Talk:Variable-frequency drive

Operating principle

I changed from RPM = {{{120 \times f}\over{p}}} TO RPM = {{{60 \times f}\over{p}}} I'm right? Minute has 60 seconds, ferquency is in Hz, so it is natural to multiplie with 60 not with 120, as is stated p is Number of pole pairs, not number of poles!

Variable frequency drives operate under the principle that the synchronous speed of an AC motor is determined by the frequency of the AC supply and the number of poles in the stator winding, according to the relation:

   RPM = {{{60 \times f}\over{p}}}

where

RPM = Revolutions per minute

f = AC power frequency (hertz)

p = Number of pole pairs(an even number)

Synchronous motors operate at the synchronous speed determined by the above equation. The speed of an induction motor is slightly less than the synchronous speed.

The above unsigned material is technically correct except that the number of pole pairs can be either an even or odd number. The previous persentation was also technically correct and, I believe, the more usual way that the material is presented. I have several USA references including that state the poles in an AC motor as poles rather than pole pairs. Is "pole pairs" the more common usage elsewhere? -- C J Cowie (talk) 15:40, 26 March 2008 (UTC)

Reference re use of "poles" vs. "pole pairs": NEMA Standards Publication (2002). Information Guide for General Purpose Industrial AC Small and Medium Squirrel-Cage Induction Motor Standards (Condensed MG 1-2002). Rosslyn, VA USA: National Electrical Manufacturers Association. Retrieved 2008-03-26. -- C J Cowie (talk) 17:58, 26 March 2008 (UTC)

The following references support the previous presentation of this material:

• Campbell, Sylvester J. (1987). Solid-State AC Motor Controls. New York: Marcel Dekker, Inc. pp. p86. ISBN 0-8247-7728-X. {{cite book}}: |pages= has extra text (help); Cite has empty unknown parameter: |coauthors= (help)
• Fitzgerald, A. E. (1983). Electric Machinery (4th ed. ed.). Mc-Graw-Hill, Inc. pp. p122. ISBN 0-07-021145-0. {{cite book}}: |edition= has extra text (help); |pages= has extra text (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Gehmlich, Dietrich K. (1967). Electromechanical Systems. Mc-Graw-Hill, Inc. pp. p296. {{cite book}}: |pages= has extra text (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Siskind, Charles S. (1963). Electrical Control Systems in Industry. New York: McGraw-Hill, Inc. pp. p223. ISBN 0070577463. {{cite book}}: |pages= has extra text (help); Cite has empty unknown parameter: |coauthors= (help)
• Smith, Ralph. J. (1971). Circuits Devices and Systems (2nd ed. ed.). John Wiley & Sons, Inc. pp. p574. ISBN 0-471-80170-4. {{cite book}}: |edition= has extra text (help); |pages= has extra text (help); Cite has empty unknown parameter: |coauthors= (help)

C J Cowie (talk) 23:07, 26 March 2008 (UTC)

Unless a good rationalization and references are provided for the current version, I will revert this section to the previous version and add the references cited above. --C J Cowie (talk) 23:18, 26 March 2008 (UTC)

I agree: "I believe, the more usual way that the material is presented. I have several USA references including that state the poles in an AC motor as poles rather than pole pairs. Is "pole pairs" the more common usage elsewhere?" My personal expirience is that severeal european university are using pole pairs, but for USA references is more common use of poles. I'm living decision to You, but mayby difference should be stated somewhere in the page becouse of european students? —Preceding unsigned comment added by 89.188.39.77 (talk) 12:53, 27 March 2008 (UTC)

Braking

My understanding is that there is a way to also use a controller like this to brake a motor by purposefully lagging the phases but it is not clear to me what the power-take-off circuit looks like in this case. Can anyone explain how regenerative breaking works in conjunction with this type of controller? —Preceding unsigned comment added by Laughingskeptic (talk • contribs) 18:03, 24 November 2007 (UTC)

When the frequency is reduced more quickly than the motor will coast down, the synchronous speed drops below the operating speed and the inherent characteristics of the motor cause it to regenerate. The power returns to the DC bus through the anti-parallel diodes in the inverter circuit. If the regenerative energy is not removed, the DC bus capacitors will charge to an excessive voltage level. Standard VFDs monitor the bus voltage and limit the rate of frequency reduction to prevent excessive regeneration. There is also a DC overvoltage trip feature that will shut down the VFD if the voltage gets too high. It is also possible to switch resistors across the DC bus for dynamic braking or return the energy to the AC line for regenerative braking. The energy is returned to the AC line using a regenerative AC to DC converter circuit. -- C J Cowie (talk) 19:19, 24 November 2007 (UTC)

There is a novel (?) application of VFD in the Prius hybrid drive. The Regen energy of course goes into the traction battery. See also [1] Shannock9 (talk) 01:49, 2 December 2009 (UTC)

Regeneration

There really should be something about regenerative braking in the main article. Cowie, can you do it? --Treekids 20:18, 4 December 2007 (UTC)

Regenerative Drives

I would consider the section on regenerative drives to be misleading. Regenerative drives are not common nor are they widely used in the United States. In 10 years I have only seen one and that was when it was being pulled out and replaced due to constant failure. Major manufacturers (such as Yaskawa) are only now beginning to offer regenerative drives but they have had problems. The picture in that section shows a drive that I have never heard of and could find no information on. Crane hoist applications in the U.S. (which is one application mentioned in that section) do not use regenerative drives 99.999% of the time - at least in my experienced estimation. Crane hoist use braking transistors and power resistors to burn off the regenerative energy. If regenerative drives are more common in other countries (which I cannot find nor have ever seen any evidence of) then that should be noted. Otherwise, regenerative drives are still a "maturing" technology. Slowchaos (talk) 01:37, 7 June 2012 (UTC)

Regenerative drives section may need improving but with the huge global emphasis on renewable energy generation in energy field, on hybrids in automotive transportation field, in electric railway transportation and so on. I therefore disagree strongly in general with your view. All Toyota Prius cars and similar hybrid cares are with regenerative drives. There is currently for example a big push for regenerative drives in building elevator industry. Common DC bus drive are also increasingly being used for regeneration in drive applications. As the cost of energy increases, regenerative drives will become increasingly attractive. If you scratch hard enough below the skin, there can be no doubt that there is a vibrant present in, and attractive future for, regenerative drives. Cblambert (talk) 22:38, 8 June 2012 (UTC)

Motor Characteristics

There really should be a few graphs/tables illustrating how the torque/power/power factor/efficiency/ are effected of when a VSD is used. —Preceding unsigned comment added by 119.11.27.116 (talk) 13:59, 3 April 2009 (UTC)

LIMs

Linear motors also use VFDs. Operating principles does not seem to cover these.

Attention?

An anonymous editor just added the "Attention" template (well, sorta kinda) and the following text:

Full speed listing:

After the initial acceleration to full speed a 2-pole synchronous motor connected to a power supply that operates at 50 Hertz (cycles per seconds) runs at 3000 revolutions per minute (RPM). If 4-poles then 1500 RPM, if 8 poles then 750 RPM, etc.

After the initial acceleration to full speed a 2-pole synchronous motor connected to a power supply that operates at 60 Hertz (cycles per seconds) runs at 3600 revolutions per minute (RPM). If 4-poles then 1800 RPM, if 8 poles then 900 RPM, etc.

As the frequency of the power supply is changed, the motor's final speed is changed accordingly.

Until they added that text, I though the article was pretty fine, albeit a bit short. Now, I definitely agree that it needs "attention".

Does anyone feel strongly that this new text shouldn't be deleted (it's more relevant to Electric motor and the "attention" sorta-kinda template removed?

Atlant 17:17, 17 July 2005 (UTC)

exactly -vega007

I deleted the "attention" but left the "full speed listing" although I think the substance of it is covered under Electric motor. I would like to give this much more attention, but this is my first day. I am working on a more general article on adjustable speed drives. C J Cowie

I say loose it. It's a description of what motors do under various frequencies. VFDs certainly provide motors with variable frequency, but this article isn't about describing how things operate when connected to a VFD. Plus, the text is non-encyclopedic. Mainstreetmark 18:38, 27 October 2005 (UTC)

Although the article isn't about describing how a motor operates when connected to a VFD, the motor performance is part of the underlying principles of VFD operation. I expanded the article with that in mind. I have more material that I will add later.

Capacitor symbol polarity appears to be reversed in the PWM_VFD_Diagram.PNG image. The '+' symbol at the bus rail doesn't conform with the direction of the capacitor symbol (the 'flat' side should be towards '+'). Zootsuite 01:25, 14 May 2007 (UTC)

I have corrected the diagram, thank you. C J Cowie 14:52, 14 May 2007 (UTC)

Re VFD Motors

There are problems with the bolded addition to the following sentence: Various types of synchronous motors offer advantages in some situations, such as the use of hall sensors to control inverter frequency and pole switching to vary the frequency to rotational speed ratio, but induction motors are suitable for most purposes and are generally the most economical choice. The use of hall sensors in VFDs is generally not related to the type of motor used. Hall sensors are used in VFD circuits for current sensing and as one of several types of shaft speed and position sensor. Pole switching is a means of changing the operating speed of an AC motor, but it is generally not used in conjunction with variable frequency drives. --C J Cowie 18:07, 12 March 2006 (UTC)

Servomotor article needed

An article on servomotors, linking to this article and to "brushless DC" motors, would be useful, to fill out the area of motor control.

It's worth mentioning that "brushless DC" motors are really synchronous AC motors, and need a variable frequency drive. For historical reasons, small brushless servomotors are referred to as "brushless DC", and larger ones (1KW and up, typically) are referred to as AC motors. Brush-type DC motors, on the other hand, take a DC input.

Newer control methods

There are newer variations on PWM control method. The standard method uses an image of the motor characteristic and pulses the frequency accordingly. Latest methods use Direct Torque Control and control the pulse width by reading the feedback from the motor. This enables individual phases to be pulsed more accurately and accounts for correction of imbalances prevalent in actual motor windings. Aroonl 03:48, 31 January 2007 (UTC)

Line and load reactors

I was wondering if we should include a section on line and load reactors and their use with VFDs. Is this common practice everywhere, or just for certain industries/regions/manufacturers? --W0lfie 19:04, 15 March 2007 (UTC)

Line and load reactors are not always needed. If the VFDs don't make up too large a percentage of the connected load, harmonic distortion of the input current and voltage may not exceed acceptable levels without input reactors. If the motor is constructed to withstand high voltage spikes and dv/dt and/or is close to the VFD, load reactors may not be necessary. In addition, built-in drive features may reduce the need for external input and/or output reactors. Also, Wikipedia is not supposed to be an instruction manual. A full discussion of the proper application, installation and operation of VFDs is likely beyond the intended scope of a Wikipedia article. C J Cowie 19:21, 15 March 2007 (UTC)

I agree, it's probably not in the scope of the encyclopedia if it's not universal. That's why I asked. It's pretty common in my industry, but I didn't want to change the article if it wasn't representative of all VFD installations. --W0lfie 02:28, 25 April 2007 (UTC)

Line and load reactors are very common in heavy industry of any kind. I am a controls technician who is considered a "drive specialist" and I do service work in almost every kind of industry imaginable. Load reactors are very common and line reactors are almost as common. These reactors are not just used for harmonic issues. Line reactors are often used to prevent short power spikes coming from the power company causing the common "VSI" drives to trip for nuisance over voltage trips. Slowchaos (talk) 01:12, 7 June 2012 (UTC)

As a further note, the use of load reactors also has little to do with harmonics and the power company. Load reactors are used to help reduce the output harmonics which helps the motor run cooler - especially with long motor leads. They will also help reduce the effects of the PWM on the motor windings.Slowchaos (talk) 17:37, 7 June 2012 (UTC)

Re latest load reactor comment: The most effective way to deal with PWM-based long lead effects is using low-pass low-pass LCR sine wave filters. Load reactors come more into play as harmonics migitation option for legacy CSI drives which are not PWM, very large legacy and new LCI drives, and six-step drives.Cblambert (talk) 22:01, 8 June 2012 (UTC)

Re latest line reactor comment: It is well known that line reactors are inexpensive first line of defence harmonics migitation option. For anyone interested in evaluating in quantitative terms the relative impact of different harmonics migitation options, you might for example download Trans-Coil, Inc.'s TCI Analyzer tool. Tool allows harmonics calculations, for power supplies with different levels of 'stiffness', and in ascending order of effectiveness, harmonics mitigation loading options that include:

• Linear loads
• Unfiltered VFD load with or without DC bus choke
• VFD load with 3% line reactor and with or without DC bus choke
• VFD load with 5% line reactor and with or without DC bus choke
• VFD load with line reactor and passive harmonic filter and with or without DC bus choke
• VFD load with center-tapped line reactor and passive harmonic filter with or without DC bus choke

There are several ways to skin harmonics issue cats, line reactors being used as not one first line of defence but also in conjunction with more effective/costly migitation options.Cblambert (talk) 22:14, 8 June 2012 (UTC)

And, yes, side benefits of line reactor admitably also includes diode-bridge protection against power line disturbances.Cblambert (talk) 05:24, 9 June 2012 (UTC)

Cable requirements

Also, I read somewhere that you should use shielded 1000V cable between the VFD and the motor. [2] for instance. Is that true? I haven't ever noticed any problems running regular unshielded 600V cable out to the motors. I couldn't find anything in the NEC at all about VFDs. --W0lfie 19:04, 15 March 2007 (UTC)

Article 430 of the 2005 National Electrical Code has a new section on Adjustable-Speed Drive Systems:

X. Adjustable-Speed Drive Systems

430.120 General. The installation provisions of Part I through Part IX are applicable unless modified or supplemented by Part X.

This section contains provisions: calling for branch/feeder conductor sizing for not less than 125% of the rated input current of the drive, permitting the drive to provide overload protection for the motor, and permitting the disconnecting means to be in the incoming lines to the drive and rated for not less than 115% of the rated input current of the drive.

Many if not most VFD manufacturer's instructions indicate that shielded motor cable is required to meet the EMI requirements of the European area. I know of at least one IEEE paper that discusses shielded motor cable and I believe recommends using it in some circumstances. I am pretty sure that John Bentley is one of the authors. C J Cowie 19:32, 15 March 2007 (UTC)

The IEEE paper is: Evaluation of motor power cables for PWM AC drives; Bentley, J.M.; Link, P.J.; Industry Applications, IEEE Transactions on, Vol.33, Iss.2, Mar/Apr 1997, Pages:342-358. It includes a discussion of insulation voltage ratings. C J Cowie 20:01, 15 March 2007 (UTC)

Uses?

This is an interesting page from an engineering standpoint, but perhaps someone could add a few sentences about what they're actually used for? —Preceding unsigned comment added by 204.11.6.125 (talk) 19:09, 28 September 2007 (UTC)

For uses, see Adjustable-speed drive. C J Cowie 22:23, 28 September 2007 (UTC)

Uses! Its everywhere. Patricularly in industries to control speed of machines [Sandeep Poddar] —Preceding unsigned comment added by 59.89.48.60 (talk) 02:38, 18 October 2007 (UTC)

Might I ask, can the vfd or similar be used for power generation? Is this used in hybrid cars? Wind energy generation? —Preceding unsigned comment added by 209.242.238.145 (talk) 21:16, 15 November 2007 (UTC)

VFDs are one option for controlling an electric motor(s) in a hybrid or electric car. I believe that there are some manufacturers presently using that approach. They have also been used in much larger electric vehicles such as electric railway locomotives. Some wind energy schemes use an induction motor controlled by a VFD as a generator. DC power from the VFD is passed to the grid using an inverter. C J Cowie 23:19, 15 November 2007 (UTC)

Links to Related Articles

I've tried to post external links to three variable frequency drive articles that could really be a great research resource. For some strange reason, they will not post, and it's not from a lack of trying. I've posted them about 5 times. The links are as follows:

Article 1: The Benefits of Variable Frequency Drives - This article outlines the energy savings, the tighter process control, and the extension of equipment life through variable frequency drives. The website can be found at http://vfds.com/vfdbenefits.html

Article 2: How to Specify Variable Frequency Drives - This article describes the process one should follow to identify what type of variable frequency drive needed for a specific application. The article also offers some alternative views on how to size drives. The article is found at http://vfds.com/vfdspecify.html

Article 3: Harmonic Mitigation Specification for Variable Frequency Drives - This article explains the importance of harmonic mitigation control and the potential damage it can do to one's electrical system. The article can be found at http://vfds.com/harmonic-mitigation.html

Can anyone offer an explanation to why I am have issues with this?

Webmaster emc123 (talk) 18:45, 14 February 2008 (UTC)

Carrier Switching Frequencies (CSF)

I had to guess that CSF refers to the switching frequency used in PWM systems. There should be a bit of wordage, or a link, explaining this term before using it in the article...... Jim, K7JEB (talk) 01:18, 3 August 2008 (UTC)

I had exactly the same problem - CSF is not explained, and some would regard the word Carrier as redundant/confusing - it's just a switching frequency. I understand that some manufacturers use the term CSF, nevertheless to me it's either a carrier frequency or a switching frequency, but not a carrier switching frequency. The carrier itself is a square wave - the electronic components may be switched but the carrier is not.

A big part of the problem is that in this application of PWM there is conceptually a modulating waveform (the sinusoid we are attempting to feed to the motor) whereas in DC to DC PWM inverters the "modulating waveform" is a flat line! So if you come to this from (say) PC PSUs you are not used to having a modulating wave therefore you never learned to distinguish the carrier by that name.

Note the article on Class D amplifiers does not use the term Carrier at all.

Perhaps more importantly the diagram with the red bars appears to be incorrect. In order to synthesize a sinusoid the first and third bar of each triplet should be narrower than the second bar. Shannock9 (talk) 22:13, 29 May 2009 (UTC)

Harmonics ... nice work people

Well, I am quite happy to see how the Powerline harmonics section of this article has grown from my first stab at it. Thanks for all the hard work on improving the article.

A secondary purpose of the section is to make light of the issue that while VFDs can improve motor efficiency and may reduce metered power usage for a business, VFDs can also be detrimental to overall power quality and to other customers on the line, possibly many miles away.

I would bet that the compensation for harmonics isn't entirely loss-free by itself.... a power company choosing to install filtering at a substation is probably losing a certain percentage of power to run the compensators and "smooth out" the misshapen power sinewave.

DMahalko (talk) 19:09, 3 November 2009 (UTC)

Did you mean "...make light of..." or "...shed light on..."? Shannock9 (talk) 00:03, 2 December 2009 (UTC)

overhauling load

• term needs explanation --Treekids (talk) 16:25, 6 July 2011 (UTC)

Wind back

The "clade" diagram takes up a lot of space and is mostly not about VF drives. The accuracy of much of the text was doubtful. Things like "AC drives can be classified to be dominated in terms of rating total of historical and current installations by the following application areas" are impossible to parse. --Wtshymanski (talk) 14:42, 31 January 2012 (UTC) I don't agree and will go on to other things. Thanks and goodbye. — Preceding unsigned comment added by Cblambert (talk • contribs) 01:41, 1 February 2012 (UTC) Cblambert (talk) 17:46, 1 February 2012 (UTC)See also entry for Luddite, which is germane to issues raised by Wtshymanski's regressive arbitrary undos.

The clade diagram is still not very helpful. It's a hodge-podge of "topologies" (which is never explained), active device types, and a bunch of brand names, none of which are definitive. The T1 to T13 designations are useless clutter. And where do cycloconverters fit in? --Wtshymanski (talk) 18:45, 12 April 2012 (UTC)

Editors should interact with each other in a respectful and civil manner. Please make specific constructive suggestions for improving the article.Cblambert (talk) 17:32, 13 April 2012 (UTC)

Editors should also write clear and organized prose. I thought the observation above was fairly lucid, would it be any more clear if it was phrased imperativly as "Remove both hodge and podge, do not confuse topology, device type and brand names, unless a drive topology is only made by one company in the world delete all brand names, rely on published sources instead of manufacturer's advertising literature, do not snow the article under with unexplained acronyms, give the reader some clue as to which of these techniques are important and why, and don't ignore the cycloconverter"? I think this vastly extended version of the clade diagram, compared with the original (and also poor) source, is not a benefit to the reader. --Wtshymanski (talk) 18:05, 13 April 2012 (UTC)

Please make specific constructive suggestions for improving the article.Cblambert (talk) 19:07, 13 April 2012 (UTC)

Topologies

Table A: Topologies new content made collapsable

Cblambert (talk) 02:08, 1 February 2012 (UTC)Here is proposal for coverage of poossible new section called 'Topologies', a 'Topology'^ being defined as 'A map-like diagram showing the elements of an AC drive and the relationships between them.' VFD Topologies LV Drive Topologies IGBT Multi‑pulse matrix eg, Yaskawa 2‑level PWM VSI drive Majority of manufacturers 3‑level PWM VSI drive eg, Yaskawa SCR Rectifier‑IGBT Inverter VVI (six‑step) drive eg, Baker-Hughes MV Drive Voltage Source Topologies Three‑level NPC drive GCT eg, ABB, GE IGBT eg, Eaton, GE-Toshiba, Siemens Multilevel CHB inverter drive IGBT eg, GE, Siemens (Robicon), Toshiba Flying‑capacitor inverter drive IGBT eg, GE-Converteam Two‑level inverter drive IGBT eg, GE-Converteam NPC/H‑bridge inverter drive IGBT eg, Toshiba MV Drive Current Source  Topologies LCI SCR eg, ABB, GE-Converteam, Siemens Rockwell Automation SGCT with AFE PWM CSR / PWM CSI drive with CME SCR + SGCT 18-pulse PWM CSI drive   Legend AFE - Active front end CME - Common mode elimination CHB - Cascaded H-bridge CSI - Current source inverter CSR - Current source rectifier GCT - Gate controlled thyristor IGBT - Insulated gate bipolar transistor LCI - Load commutated inverter LV - Low voltage MV - Medium voltage NPC - Neutral point clamped PWM - Pulse-width modulation SCR - Silicon controlled rectifier SGCT - Symmetrical gate controlled thyristor VSI - Voltage source inverter VVI - Variable voltage inverter ^ Refer to http://www.wmea.net/Technical%20Papers/GE%20Medium%20Voltage%20Drives.pdf PSS: Refer also to the paper Jarc, Dennis - A Graphical Approach to AC Drive Topology Classification. Cblambert (talk) 05:39, 1 February 2012 (UTC) Distinction made between LV 2-level PWM VSI drive and 3-level PWM VSI drive categories. Yaskawa is one of the few manufacturers to offer LV 3-level PWM drive, major advantanges over LV 2-level PWM drive including: - reduced common mode noise - reduced audible noise - reduced cable length issues - reduced bearing failures. See for example http://www.yaskawa.com/site/dmdrive.nsf/(DocID)/SKUS-5YBHWZ/$File/eLV.G7.01.exe http://www.yaskawa.com/site/dmdrive.nsf/(DocID)/SKUS-5YBHWZ/$File/eLV.G7.01.exe Cblambert (talk) 01:03, 2 February 2012 (UTC) Cblambert (talk) 01:29, 2 February 2012 (UTC) Cblambert (talk) 07:03, 17 February 2012 (UTC)

VFD Types

For the record this is how VFD Types section read before recent 'wind back' VFD types can be expressed in terms of the range of variable speed drives shown in the following diagram.

Table B: VFD types new content made collapsable

Variable Speed Drive Fixed speed motor Mechanical variator Fluid coupling Magnetic coupling Eddy current coupling Electrical DC motor (^1) Electronic commutation DC Voltage source (PWM) Mechanical commutation Thyristor converter Electro-mechanical drive AC motor Induction (^2) Wound rotor (WRIM) Electro-mechanical Slip energy recovery (Kramer), double-fed Cage rotor Matrix Current source (CSI) Variable voltage (VVI) Variable voltage (PWM VSI) Synchronous(^2) Wound field Load commutated (LCI) Cycloconverter CSI, VSI (^3) Permanent magnet rotor (PM) Axial or disk Radial Interior Surface Sinusoidal (PMSM) Trapezoidal (BLDM) Reluctance machine (SyRM) Wound field (WFSM) Variable reluctance (VRM) (^2) Switched reluctance (SRM) Stepper   Notes: ^1 - Separately excited, shunt, series, compound ^2 - Rotating or linear ^3 - CSI, VSI possible but unusual compared to LCI AC drives can be classified to be dominated in terms of rating total of historical and current installations by the following application areas : Induction motor applications Variable-voltage inverter (VVI) or 'six-step' drives Other voltage-source inverter (VSI) drives Current-source inverter (CSI) drives Synchronous machine applications VSI and CSI drives (^3) Cycloconverter drives Load-communicated inverter (LCI) drives. In a basic VVI drive, the DC output of the SCR-bridge rectifier is smoothed via DC link capacitor bus circuit to supply quasi-sinesoidal six-step voltage input to the inverter. In a basic VSI drive, the DC output of the diode-bridge rectifier stores energy via DC link capacitor bus circuit to supply stiff voltage input to the inverter. In a basic CSI drive, the DC output of the SCR-bridge rectifier stores energy via DC link inductor circuit to supply stiff current input to the inverter. A cycloconverter drive has no AC-to-DC converter and instead connects each output terminal to the appropriate input phase, making up the desired variable-frequency output waveforms by selective commutation from the fixed-frequency input waveforms. In a basic LCI drive, the DC output of the SCR-bridge converter stores energy via DC link inductor circuit to supply stiff quasi-sinesoidal six-step current input to a second SCR-bridge's inverter and an over-excited synchronous machine. Most packaged AC drives are VSI-PWM type using pulse width modulation to control the motor's frequency in scalar or open-loop Volts-per-Hertz (V/Hz) operating mode. Higher performance drives have been developed offering field-oriented control (FOC), closed-loop speed control with slip compensation, or direct torque control (DTC). PWM is not normally used with DTC. VVI drives have largely been replaced by VSI-PWM drives. CSI-PWM is also significant in high power AC drive applications. VSI-PWM drives are often incorrectly referred to as PWM drives. AC drives used in variable torque loads applications have historically been associated with general purpose 2-level PWM inverter topology in open loop V/Hz control. V/Hz control is also sometimes referred to as scalar control or variable voltage, variable frequency (VVVF) control. Higher performance load applications are increasingly been been used for AC drives with multi-level and cellular inverter topologies and closed loop and sensorless vector or DTC control.. The expectation is that vector control will eventually universally replace scalar control for AC drives.

Cblambert (talk) 07:26, 17 February 2012 (UTC)

Energy Savings

I just want to comment that VFD's not only provide energy savings for high horsepower motors, it also assist in controlling non-steady steady state operating system.

For example: if there is a sudden load change on a pump motor (ie sudden pressure drop), the VFD can slow the motor down so the pump does not lose its prime (ie cavitation)

This is not an energy savings, per se, but I think it is worth mentioning in this talk page.

I support your suggestion. This is sort of thing Talk section 'Benefits section need shoring up' below is driving at. Other benefits high horsepower VSDs have include:

• ability to 'catch a spinning column of water or oil' after outage
• slurry pipeline applications use of VFDs primarily to optimize pump/pipeline metal wear.

Cblambert (talk) 17:46, 25 April 2012 (UTC) Deekayfry (talk) 15:38, 25 April 2012 (UTC)

Table C: Energy Savings new content made collapsable

For the record, recent 'Wind Back' to Energy Savings section undid the following contribution: It is estimated that: 60-65% of the USA's grid energy is used to supply motive power loads about 75% of which in turn are variable torque fan, pump and compressor loads About 3% of all AC motors are provided with AC drives 18% of the energy used in the 40 million motors in the U.S. could be saved by efficient energy improvement technologies such as VFDs An energy consumption breakdown of the global population of AC motor installations is as shown in the following table: Global Population of Motors, 2009 Small General Purpose - Medium-Size Large Fractional kW, >1W 3/4 to 375kW >375kW, <100MW 1-ph., LV to ~240V 3-phase, LV to ~1kV 3-ph., MV, >1kV 9% energy 68% electrical energy 23% energy 2 billion Total stock: 230 million 0.6 million

Cblambert (talk) 07:32, 17 February 2012 (UTC)

Main Part of VFD Writeup

Table C: Main Part new content made collapsable

For the record, this is how 2nd paragraph of main Variable-frequency drive writeuplooked like before recent 'Wind Back' undo: Manufactured in a wide range of ratings and topologies, variable-frequency drives are used in a wide number of applications to control conveyors, divertors, palletizers, rotary kilns, fans, pumps, extruders, centrifuges, compressors, winders, chippers, cranes, punch presses, lifts, elevators, escalators, pulpers, refiners, shredders, chillers, thrusters, propellers, agitators, mixers, oxidizers, mills, equipment associated with wind generation, wind tunnel, locomotion, test stand and cogeneration installations, and so on.

Cblambert (talk) 07:40, 17 February 2012 (UTC)

VFD Technology's Importance

I propose new section something along the lines of 'VFD Technology's Importance' based on pronouncements such as made at recent Workshopon Power Elctronics for Industrial Applications and Renewable Energy Conversion by Professor Bamil Bose in the keynote address, 'Energy Scenario and Impact of Power Electronics in the 21st Century'^, that "the role of power electronics in our society in future will be as important and versatile as computers and information technology today" . . .!

In regard to VFD technology's important, I also draw attention to the fact that a search today of IEEE Xplore ditigal database shows 9,241 records for the term 'Adjustable-speed drive'.

^ http://www.peia2011.com/downloads/Bose_fullpaper.pdf Cblambert (talk) 04:17, 1 February 2012 (UTC) Cblambert (talk) 04:18, 1 February 2012 (UTC) Cblambert (talk) 04:40, 1 February 2012 (UTC) Cblambert (talk) 05:11, 1 February 2012 (UTC) Cblambert (talk) 05:34, 1 February 2012 (UTC) Cblambert (talk) 05:35, 1 February 2012 (UTC)

Relevance of content in benefits section

I am primarily an observer here but wanted to create opportunity for discussion of the relevance of the content in Benefits section. Jojalozzo 18:03, 3 February 2012 (UTC)

The relevance goes something like this:

• most of industrial production is used by AC motors
• AC motors are mostly fix-speed (97%)
• AC motors therefore waste a lot of energy
• It is estimated that ~1/5 of world's electrical motive energy could be saved by technologies such as VSDS
• Therefore it is important that these industrial production energy savings be placed in perspective.

See section immediately above VFD Technology's Importance, especially about power electronics being as important in future as communications and computers are now.

Treatment in benefits could well be in sub-section of benefits Dsection.Maybe wording could be improved accordingly. Cblambert (talk) 20:20, 3 February 2012 (UTC)

Second Wholesale Undo by User Wtshymanski (UW)

I am fairly new to making contributions to Wikipedia so I am puzzled by User Wtshymanski's wholesale ratcheting back of contributions in the past few days, including the one earlier today, which will not of course do. And I accordingly look forward to getting to the bottom of any further such arbitrary actions on User Wtshymanski' part. Best regards all Cblambert (talk) 20:33, 3 February 2012 (UTC)

• Postscript: See also in this regard http://www.wikirage.com/editor/Wtshymanski/

Cblambert (talk) 22:04, 3 February 2012 (UTC)

Encyclopedia articles should be concise, comprehensive, and well-organized. Instead of dumping bullet-form statistics on the user, it would be better form to be phrasing this as English prose. The tables of "classification of drives for AC machines" aren't relevant to this article since it is talking about motor types, it's also mis-spelled ("rotaring" is not an English word). The classification also has pages of acronyms, few of which are useful to an encyclopediac overview of this topic. The clade diagram is orignal research and appears to arbitrarily collect types, again with far too many acronyms to be useful to the general reader. The "Legend" for the clade diagrams repeats the text in the clade diagrams. --Wtshymanski (talk) 22:29, 3 February 2012 (UTC)

A much more comprehensive list of edits, free from advertising, is available from each editor's contribution pages, such as [3] or even [4]. --Wtshymanski (talk) 22:35, 3 February 2012 (UTC)

With all due respect, whoever you are you, you are completely out line. Your comments need to be professional, which they currently aren't.CblambertI have corrected the 'rotating' typo. Many thanks. (talk) 23:19, 3 February 2012 (UTC)

Re tables, refer to http://en.wikipedia.org/wiki/Wikipedia:Embedded_list

Re articles, refer to http://en.wikipedia.org/wiki/Wikipedia:Good_article_criteriahttp://en.wikipedia.org/wiki/Wikipedia:Good_article_criteria

Re original research, there is no original research; all content is based on authoritative sources.

Re Legend, legends were duplicated in tables intentionally and could easily be changed to suit user preferences.

Re acronyms, in tabulation format it would be tedious to have to repeat 'Pulse-width modulation' so many times. VFDs are complex subject as the very similar article http://en.wikipedia.org/wiki/Current_source_inverter intimates. Right balance is needed between acronyms and unnecessarily repetitive long terms. This can be changed to suit user preference.

Re advertising, there is none, examples of firms being mentioned without value judgment for specific topologies based on public sources such as Bin Wu's IEEE 2006 book and other public sources. Firms' names can easily be removed to suit user preferences. Naming of firms at the outset helps anchor topologies to viable VFD offering, not to theoretical topologies.

Re table of classification of drives for AC machines, references cited (EuroPump and Bose 2006) make clear the importance of mapping drives to machines, the two being symbiotically related.

Cblambert (talk) 17:12, 4 February 2012 (UTC)

I don't think these additions to the article are well organized or properly referenced, and I don't think they help the reader understand the topic. --Wtshymanski (talk) 17:43, 4 February 2012 (UTC)

You are entitled to your opinion. The new content is organized according to authoritative sources. New content may raise issues needing development but that is the price we all have to pay in dealing with difficult complex topics. I stand by my subtantial contributions as being offered in earnest. Cblambert (talk) 18:57, 4 February 2012 (UTC)

Postscript: Note that my emphasis has been one trying to provide a better answer to the 'VFD Types' question, the first priority being naturally enough on accuracy and completeness. In that regard, it is not enough to make unsubstantiated generalizations about new content. What is needed at this stage is, a la 'form follows function', specific comments as to what it is exactly that one disagrees with about VFD Types' accuracy and completeness.Cblambert (talk) 23:19, 4 February 2012 (UTC)

Cblambert (talk) 22:01, 15 February 2012 (UTC)For the 4th time now, User Wtshymanski (UW) yesterday made arbitrary wholesale deletions to my contributions to article's two sections, 'Energy Savings' and 'VFD types'. Which I have again restored because:

• it is not enough for UW to make sweeping unsubstantiated generalizations each time expressed in different terms but always with same all-content-deleted result
• I accordingly look forward to specific comments as to what exactly it is that is not accurate or complete about the two sections but especially about 'VFD types' sectioIn's accuracy and completeness.

Also, I would be most appreciative to read others' comments about this recent Talk discussion and associated new contributions.

Best regards all

I have restored latest wholesale undo by UW for the reasons mentioned earlier here, and especially in terms of previous indent's comments. Cblambert (talk) 19:58, 11 March 2012 (UTC)

I have restored today's wholesale undo by UW. UW needs to offer constructive alternative to the information provided in contribution starting with specific comments as to the accuracy and completeness of 'Classification of Drives for AC Machines'.Cblambert (talk) 23:35, 11 March 2012 (UTC)

It's called "editing", we do a lot of that here. Can we not find more reliable sources than PowerPoint salesman slides, especially when at least one of the salesmen thinks that all VFAC drives must rectify to DC before converting to AC? The clade diagrams are horrible and I've tried to remove some of the horror, but it was more work than it was worth; they are still ugly and confusing. We shouldn't use templates that are meant to be used on user pages or talk pages, not in articles. It would be better to explain drive types in (short clear) English instead of sales-pitch-ese. You know, say things like " A current-source inverter uses an inductor between the rectifier and the inverter stages" instead of whatever horrible sales patter mumbo-jumbo is in here now.--Wtshymanski (talk) 15:16, 13 March 2012 (UTC)

Cblambert (talk) 17:45, 13 March 2012 (UTC)

Ugly charts

Those are some really ugly looking charts. The information pushes off the right edge of the screen unnecessarily because the heading branches don't nest subheadings underneath. Excessive abbreviation isn't helped by the table below it all.

Bullet lists would handle the data much more compactly, with greater readability, and allow for removal of all abbreviations, because long lines can be permitted to wrap around the page.

Applicable VFD types, listed by machine class

• Induction motor
  • Cage rotor
    • Current source inverter
    • Matrix
    • Voltage source inverter
    • Variable voltage inverter
  • Wound rotor induction motor
    • Electro-mechanical
  • Doubly fed electric machine
    • Slip energy recovery (Kramer/Schreiber)
• Synchronous motor
  • Wound field synchronous machine
    • Current source inverter
    • Cycloconverter
    • Load commutated inverter
    • Voltage source inverter
  • Permanent magnet rotor
    • Axial or disk
      • ?
    • Radial
      • Interior
        • ?
      • Surface
        • Trapezoidal Brushless DC electric motor, Sinusoidal Permanent magnet synchronous generator
          • Voltage source inverter
  • Synchronous reluctance machine
    • Voltage source inverter
• Variable reluctance machine (Rotating or linear)
  • Switched reluctance motor, Stepper motor
    • Voltage source inverter

I don't claim to know what all these terms mean but it appears some types are either skipped or incomplete, which I've marked with ?. If there's no information available then the branches should likely be removed as they add nothing to the article.

DMahalko (talk) 17:51, 13 March 2012 (UTC)

Matrix means nothing to me. Needs a wikilink. Maybe this? Sparse matrix converter

Similarly Electro-mechanical is vague and meaningless. Maybe this? Electromechanical drive

DMahalko (talk) 18:02, 13 March 2012 (UTC)

The machine classification is derived in great great part from Bose (2006) FIGURE 6.1 Classification of machines for drives. Matrix drives's are mentioned in several of article's reference and is manufactured by Yaskawa. Have fun.96.52.198.210 (talk) 18:38, 13 March 2012 (UTC)

I've always disliked the clade diagrams for this article. They are meant to show inheritance or derivation from base types - the tree strucure does not well describe the attributes of VFDs, which can be orthoganal. Plain old tables would be much better. Describing the types in English would be best yet. SOme of the terms are unfamiliar to me, which either means the creator knows more than I do, or less than I do. --Wtshymanski (talk) 19:18, 13 March 2012 (UTC)

Accuracy and completeness of machine classification and topologies tables

New section started to keep the disussion at the professional level. Re clade diagrams:

• Refer to VFD article reference at link http://www1.eere.energy.gov/industry/bestpractices/pdfs/variable_speed_pumping.pdf, Figure ES-7. Types of Variable Speed Drives, which is also very similar to Bose's machine classification.
• I am not personally hung up on their use.
• I am not convinced that collapsable tables cannot be used - that is not the way I read it.
• Article can't have it's cake and eat it to and collapsable table sure is convenient as in the case of Motors template as the bottom.
• For topologies, see especially article's Wu reference, last slide (slide 159), link at http://www.ee.ryerson.ca/~bwu/seminars/pesc05_seminar.pdf, see also references by Klug and Paes.
• There is a 'wealth of information about these and other related issues out there which hasn't yet been mined.Cblambert (talk) 22:53, 13 March 2012 (UTC)

Well, Template:COT says in part The collapse top template and its paired template collapse bottom are used for placing a collapse box around a talk page discussion, especially when the content contains complex wikimarkup such as tables. which seems a pretty direct indication that it was meant for talk pages, not articles. If these horrible line diagrams were actually good illustrations, we wouldn't have to collapse them. --Wtshymanski (talk) 23:12, 13 March 2012 (UTC)

Ah, after looking at that PDF, I see real problem now. Cblambert, you are confusing this article Variable-frequency drive with Variable-speed drive which is what that PDF is about. The table/chart/clade doesn't belong here but rather in the other article. This article is a subtype of variable speed drive, of which there are many beyond just electronic means. That DoE PDF says this right in the 2nd paragraph of the first page:

Speed can be controlled in a number of ways, with the most popular type of variable speed drive (VSD) being the variable frequency drive (VFD).

And mechanical methods are included in the original diagram which you've cropped out to make it seem to fit here. DMahalko (talk) 23:20, 13 March 2012 (UTC)w

Were are all trying to solve a problem. And yes there needs to be some overlap in order to be able to define the interfaces between adjacent articles. There is no one way perfect way to go about this. People are actual looking at the references. That is really good.Cblambert (talk) 23:33, 13 March 2012 (UTC)

I is what Manual of Style has to say about scolling and collapsible stuff:

"Scrolling lists and boxes that toggle text display between hide and show should not conceal article content, including reference lists, image galleries, and image captions. They especially should not be used to conceal "spoiler" information (see Wikipedia:Spoiler). Collapsible sections or cells may be used in tables that consolidate information covered in the main text, navboxes, infoboxes, or chess puzzles. When scrolling lists or collapsible content are used, take care that the content will still be accessible on devices that do not support JavaScript or CSS."

In my view, first priority, is accuracy and completeness. Then, someone can prepare a format suitable for everybody. Collapsible with clade would suit me because it can easily be modified and does not intrude. But I'm easy on exact table format be it clade and/or collapsible. Cblambert (talk) 23:52, 13 March 2012 (UTC)

Just so we're clear, I am not confusing this article. Bose's diagram targets ALL VFDs. variable_speed_pumping.pdf reference diagram shows all variable speed drives, which is why, following discussion, mechanical ones were cropped.Cblambert (talk) 00:16, 14 March 2012 (UTC)

Explain what low and medium voltage mean in VFD world. (NEC defines these as "high voltage")

Recent changes related to previous line here were restored to previous version because such barebones legend entries should not be cluttered with detail but should instead be dealt with separately in the article. Also, cursory search on the Internet can show that medium voltage is indeed proper parlance for motor controls generally and drives in particular.Cblambert (talk) 03:53, 14 March 2012 (UTC)

Cblambert, I'll defer to your opinion on what the legend should and shouldn't contain. But I'm not sure how useful the VFD type tables are as presented: they're too terse to be intelligible to non-experts, yet an expert will already know the information. Somehow, it'd be nice to capture the same information in a format that provides more opportunity for explanation, such as narrative text. Motor control terms of art which have unexpected meanings (like 6KV being "medium voltage"), really deserve an introductory explanation. Olawlor (talk) 08:19, 14 March 2012 (UTC)

We need clear English text, otherwise all the acronyms make it look like someone is transcribing a box of Alpha-Bits. --Wtshymanski (talk) 13:19, 14 March 2012 (UTC)

These are all excellent questions. It could be that the tables are the end product with appropriate text introduction ahead, tables acting as summary.Cblambert (talk) 16:40, 14 March 2012 (UTC)

Indeed, maybe the tables and legend are just sort of a long to medium term checklist to identify VFD article gaps.Cblambert (talk) 16:52, 14 March 2012 (UTC)

I am actually in favor of populating the legend with English text to accomplish this long to medium term gap-filling objective.Cblambert (talk) 17:12, 14 March 2012 (UTC)

Article's Ref. 13^ defines (on slide 3) AC drive topology as a 'A map-like diagram showing the elements of an AC drive and the relationship between them.', which until this week used to be referenced with Table 2. This definition cries out for the VFD article to come up with:

• a generalized topology diagram such as the one on slide 2 of Ref. 13
• a series of topology diagrams to make sense of the various different available topologies, all more or less along the lines of the topology article but for VFD topologies instead.Cblambert (talk) 18:36, 14 March 2012 (UTC)

^ TMEIC link as http://tmeic-ge.com/upload/library_docs/english/MV_AC_Drive_Topology_Analysis_1143643595.pdf

You know, just because it's in a book somewhere doesn't mean the idea is any good. There's no *relation* between the various kinds of drive that is shown by these bogus clade diagrams. They are meant to show *families*, so you can see the two-toed sloth is a descendant of the 3-toed sloth and a distant cousin of the once feared Antarctic man-eating sloth. Drives don't classify like that. --Wtshymanski (talk) 20:59, 14 March 2012 (UTC)

It appears that no amount of referencing interests so people you so I refer again to Bose and variable_speed_pumping.pdf Cblambert (talk) 21:33, 14 March 2012 (UTC)

Them diagrams completely fail to include linear motors. Where do they fall in the evolutionary tree? DMahalko (talk) 21:56, 14 March 2012 (UTC)

In Table 1, the three 'Machines' types are suffixed with '^^^', which in the Legend signifies 'Rotating or linear', all in accordance with Bose (2006) p. 328.Cblambert (talk) 22:21, 14 March 2012 (UTC)

Actually, now that the "drives by topologies" diagram now contains manufacturer info, I find it a lot more useful. Cblambert, when the content is basically done, let me know and I can try to reformat it as a more readable table. I'm also trying to figure out the commonalities of all the topologies enough to draw a useful generic system diagram: but there are a lot of options between {diode or thyristor rectification} x {inductor or capacitor energy storage} x {transistor or thyristor inverter} x {multi levels}. Plus I'm realizing quite how out of my depth I am in this stuff... (Off topic: I ordered my first VFD today! A little 1.5kW 240V unit for my lathe.) Olawlor (talk) 11:00, 17 March 2012 (UTC)

Congratulations on your own new VFD. Be safe with the lathe. There is no hurry to reformat the clade-based tree structure, which is easy to modify. First priority in my view is as you suggest to start with a generic topology diagram along the lines possibly of slide 2 of TMEIC ref (now ref 13). It could be that in long run there would need to be several topology diagrams (possibly at the extreme as a separate Wikipedia article . . . ?). Re being out of one's depth, this is exactly what a Wikipedia article seeks to do -- to demystify something that is actually quite complex into something that is understandable to the layman or laywoman. Still in brainstorm mode, at the highest level of detail, a generic topology might want to keeep in mind Fig 1 of the WEG article at http://catalogo.weg.com.br/files/wegnet/WEG-medium-voltage-industrial-variable-speed-drives-technical-article-english.pdf . . .

Cblambert (talk) 16:50, 17 March 2012 (UTC)

Topology diagramming

Article's Ref. 13^ defines (on slide 3) AC drive topology as a 'A map-like diagram showing the elements of an AC drive and the relationship between them.', which until this week used to be referenced with Table 2. This definition cries out for the VFD article to come up with:

• a generalized topology diagram such as the one on slide 2 of Ref. 13
• a series of topology diagrams to make sense of the various different available topologies, all more or less along the lines of the topology article but for VFD topologies instead.Cblambert (talk) 18:36, 14 March 2012 (UTC)

^ TMEIC link as http://tmeic-ge.com/upload/library_docs/english/MV_AC_Drive_Topology_Analysis_1143643595.pdf

I have created this sub-section to highlight perceived importance of topology diagram or diagrams as mentioned earlier today. Finding easy way to make such topology diagram(s) would be very valuable for the article.Cblambert (talk) 01:17, 15 March 2012 (UTC)

Cblambert (talk) 05:29, 15 March 2012 (UTC)

Benefits section needs shoring up

I have always felt that article's 'Benefits' section needed shoring up in terms of:

• Sub-sections beyond Energy Savings and Torque Control
• In particular, DC vs. AC drive comparison table of Torque Control sub-section should become a separate distinct sub-section of Torque Control sub-section.
• DC vs. AC drive comparison table simply does not do justice to the wealth of info from the likes of ABB, Powertec, Reliance and others on the issue to the point that it should be scapped unless something major is done to improve it.Cblambert (talk) 00:51, 14 March 2012 (UTC)

Re shoring up beyond Energy Savings and 'Torque Control', I was for example amazed to find out about my neighbour's model airplane not only being fitted with not only two elaborate remote-controlled 3-phase VFDs (each smaller than a match book) but VFDs that could turn the propeller at 60,000 rpm!!!Cblambert (talk) 01:10, 14 March 2012 (UTC)

Better Introductory Figure?

A typical application of a variable-frequency drive (VFD): convert fixed line frequency input power into variable-frequency 3 phase output power, as commanded by a speed control line.

Cblambert, would you care to discuss your wholesale revert of my work on 16:26, 14 March 2012‎? The existing system diagram doesn't clearly illustrate (1) multipole inputs and outputs nor (2) actual variable-frequency output (the output signal just looks like a quantized sin wave). For discussion purposes, I've attached my figure here. Any other editors care to chime in as to whether this figure would improve the article? My goal is to briefly convey what on earth a VFD does before going into the gory details. Olawlor (talk) 08:32, 15 March 2012 (UTC)

Maybe image in System Description should be shown at the beginning. I don't think the quality of the new image is adequate. New image is misleading in showing only 1-phase on the input and saying it is 2-phase. Better to come up with a topology drawing to start making sense of all these different topologies. With all due respect, new image does not in my view make the grade. Need something that is less amateurish.Cblambert (talk) 15:59, 15 March 2012 (UTC)

I screwed up in the image's title saying the split-phase input was "2 phase." Mea culpa. But the specific case I was illustrating was a typical industrial drive converting split-phase 240 or 480 (180 degrees out of phase) into fast (10KHz) IGBT PWM-switched inductance-filtered three phase output (120 degree phase separation) to drive a three phase motor. The figure shows the 180 degree and 120 degree phase separation accurately. This is by far the most common application of low-horse VFDs today (http://ecmweb.com/mag/electric_understanding_variable_speed_4/), providing speed control commanded via either a manual voltage divider knob or CNC analog output. They even do closed-loop by monitoring the current flow, to adjust the PWM in "flux vector" mode. A typical model like this is the Westinghouse/Teco EV series (though there about a hundred current manufacturers). Who uses VVI nowadays--aren't most modern machines PWM? What specific model number/application is the "System Diagram" trying to illustrate? Olawlor (talk) 22:13, 15 March 2012 (UTC)

I added a three-phase input figure, Electrical VFD Diagram, 3phase to 3phase.svg, if that'd be more useful. Most heavy industrial applications start from three phase, and the "three in, three out" wiring should help focus attention on the varying frequencies.Olawlor (talk) 23:03, 15 March 2012 (UTC)

Also, I would think that any new image along the lines you propose, Olawlor, would detract from, and be confusing to, existing System Description image. Any new image should in my view be thought up in terms of also being acceptable for System Description purposes. That is, only one image for both purposes. Note incidently article's ref. 13 by Waide of International Energy Agency (link at http://www.iea.org/papers/2011/EE_for_ElectricSystems.pdf) uses on p. 53 the System Description image for it's layman's treatment of VFDs.Cblambert (talk) 16:55, 15 March 2012 (UTC)

Note also that System Description image's VFD output is showing neither a quantified sine wave or 'quantized sin' wave but is, strictly-speaking, showing the output for a 6-step or variable voltage (VVI) VFD's inverter, which is why it is called a 6-step VFD. But this is irrelevant to the layman who is starting to read VFD article . . . Isn't it? Why the random waves in the new image? Layman would surely wonder why there are 2 random waves on the input and 3 random waves on the output. Cblambert (talk) 17:14, 15 March 2012 (UTC)

Sure, the quantization is just an artifact of a VVI's crappy D/A conversion.Olawlor (talk) 23:03, 15 March 2012 (UTC)

Take a look at Fig 1, Principles of Speed Regulation, from Schneider-supplied link at http://www2.schneider-electric.com/documents/technical-publications/en/shared/automation/automation-information-networks/ect208.pdf, which in most simple terms introduces the idea that, like in the case of a home thermostat, any speeed control must have a way to:

• set the desire speed to a certain value
• get feedback as to how the 'regulator' output in comparison to the desired value
• accordingly make changes to the drive.

It would be useful for the article to deal this the 'principles of speed regulation'. Cblambert (talk) 19:26, 15 March 2012 (UTC)

Feedback is nice for efficiency and smoothness (e.g., flux vector control), but you can definitely run a useful system open loop as well--it just makes your three phase motor act like a stepper. Olawlor (talk) 23:03, 15 March 2012 (UTC)

I think the new image is uncceptable. It adds nothing that could not be included in System Description (SD) image. That the SD image happens to be VVI is incidental. Largest electical submersible pumping (ESP) application VFD manufacturer in the world still uses VVI; here again article should be generally neutral about VVI within the grand scheme of the VFD universe. Article treatment should be neutral as to issues of input voltage rating, number of phases. Principle of speed control is universe to all VFD no matter if open loop or closed loop. VFD always has to check how speed setting is doing, as in a home thermostat. Sometimes the checking is done at the motor, sometime at the VFD output. But the very nature of VFD operation is that there is setting of the speed/frequency and checking how the VFD is doing in achieving that objective. Any new all-purpose SD-like image should be relatively neutral number of phases on the input, number of wires on the input or output, unusual waves, and so on. Some LCI drives for example have 12-pulse/6-phase output. It does not look to me that the new image is going in right direction. Existing SD image should cover your stated objective.Cblambert (talk) 00:02, 16 March 2012 (UTC)

I've looked at the http://ecmweb.com/mag/electric_understanding_variable_speed_4/ article, which in general is a good one as most ECM articles are. But this article cannot be covered by one little image as you suggest. What is needed to so justice to the article is to go about in a systematic fashion including in terms of topologies article's Table 2, defining what is meant by VSI, CSI, LCI, matrix, cycloconverter, and so on, and so on. Which is very competely different then the new image you are suggesting.Cblambert (talk) 00:32, 16 March 2012 (UTC)

VFD history

(Comment edited as follows as it occurs to me that original text may contravene Professor Bose's copyright.)

This AC drive article would benefit from having a detailed history section along the lines of of the excellent history section off provided in the Transformer article. Professor Bose's 2006 book provides in Fig 1.16 (to use as broad outline for discussion purposes) the following four generations of solid-state power electronics:

• 1st Generation (1958–1975) (Thyristor Era)
• 2nd Generation (1975–1985)
• 3rd Generation (1985–1995)
• 4th Generation (1995–)

Professor Bose uses an impressive number of Wikipedia entries to describe these four generation including the following entries: Diode, Thyristor, Triac, Power BJT, power MOSFET, GTO, Microprocessor, ASIC, PIC, advanced control, IGBT, DSPs, advanced control, IGCT, cool MOS, sensorless control, AI, fuzzy logic, and neural networks (Only a handful of other terms are not Wikipedia entries.)

Anyone interested in working on such VFD history section?Cblambert (talk) 21:59, 15 March 2012 (UTC)

Ref 17 (Rashid, ed.) has a good historical review on p. 882 spanning 1886 to 1998 by Dr. Yahya Shakweh. Incidently Bose's 2006 book recommends Rashid as a good power electronics reference.Cblambert (talk) 06:36, 17 March 2012 (UTC)

An interesting VFD history is also provided by Professor Bill Drury at the beginning of his book The Control Techniques Drives and Controls Handbook.Cblambert (talk) 02:04, 20 March 2012 (UTC)

Editors should interact with each other in a respectful and civil manner.

This Wikipedia pillar is sorely lacking a the part of some editors in this an other similar associated articles.Cblambert (talk) 20:13, 17 March 2012 (UTC)

'Green energy' section

It would be nice to come up with a 'Green energy' section in the form of possible a HEV Hybrid Block Diagram at link http://twinkle_toes_engineering.home.comcast.net/~twinkle_toes_engineering/hybrid_car.htm#Toyota/Ford/Lexus hybrid block diagram (2nd link in link from the top).Cblambert (talk) 02:52, 21 March 2012 (UTC)

Citation footnotes - Some comments

Re: http://www.emcsolutions.com/article_vfd_benefits.html

• One of the citation footnotes which I did not clean up. Citation could be done away with.

Re: "Guide to Variable Speed Drives - Technical Guide No. 4". Technical Guides (ABB).

• Good technical guide. Copyrighted material

Re: "DC or AC Drives? A guide for users of variable-speed drives (VSDs)". ABB

• Good technical source. Does not say copyrighted but evidently copyrighted.

Re: http://www.optimacs.com/reports/Understanding%20the%20control%20system.pdf One of the citation footnotes which I did not clean up. Citation could be done away with.

^ "AC and DC Variable Speed Drives Application Considerations". Rockwell Automation.

• Good technical source. All rights reserved.

Re: "A Guide to Standard Medium Voltage Variable Speed Drives, Part 2". ABB

• Good technical source. Written by Ewan Morris and David Armitage. Evidently copyrighted.

Re: Paes, Richard (June 2011). "An Overview of Medium Voltage AC Adjustable Speed Drives and IEEE Std. 1566 – Standard for Performance of Adjustable Speed AC Drives Rated 375 kW* and Larger".

• Paes has long been associated with A-B

Re: ACS800 Catalog - Single Drives 0.55 to 5600 kW. ABB.

• Old citation that I recently cleaned up to show that upper end of LV drive rating capacity is between 5 and 6 MW

Re: Lockley, Bill; Wood, Barry, Paes, Richard, DeWinter, Frank (Jan.-Feb. 2008). "Standard 1566 for (Un)Familiar Hands".

• Paes has long been associated with A-B; DeWinter has long been associated with A-B and Siemens

Re: Klug, Dieter-Rolf; Klaassen, Norbert (2005). "High Power Medium Voltage Drives - Innovations, Portfolio, Trends".

• Authors were with Siemens

Re: DuraBilt5i MV Topologies Comparisons & Features-Benefits". TMEIC.

• Excellent technical source. Copyrighted material

^ "Guide to Harmonics with AC Drives - Technical Guide No. 6". Technical Guides (ABB).

• Good technical guide. Copyrighted material

Re: Skibinski, Gary; Breit, Stephen (2004). "Line and Load Friendly Drive Solutions for Long Length Cable Applications in Electrical Submersible Pump Applications".

• Skibinski has long been associated with A-B; Breit has long been associated with GE/Wood Group

Re: "Application Report Long Drive/Motor Leads". Yaskawa Electric America, Inc.

• Good technical source. Does not say copyrighted but evidently copyrighted.

Re: "A-B Reliance GV3000 FAQs Who Cares About Carrier Frequency?".

• Good technical source. Does not say copyrighted but evidently copyrighted.

Re: "Bearing Currents in Modern AC Drive Systems - Technical Guide No. 5". Technical Guides (ABB).

• Excellent technical guide. Copyrighted material

Re: "EMC Compliant Installation and Configuration for a Power Drive System - Technical Guide No. 3". Technical Guides (ABB).

• Excellent technical guide. Copyrighted material

Cblambert (talk) 21:10, 12 April 2012 (UTC)

I nearly forgot.

Re: Drury, Bill (2009). The Control Techniques Drives and Controls Handbook (2nd ed.).

• 2nd edition of Institution of Engineering and Technology sponsored, copyrighted book, Control Techniques being owned by Emerson Industrial Automation, Dr. Drury being Royal Academy of Engineering Visiting Professor of Innovation at University of Bristol. Still this is an excellent source.

Cblambert (talk) 22:13, 12 April 2012 (UTC)

Note that also regarding above DuraBilt5i/TMEIC citation, 'TMEIC' should read 'TMEIC GE', TMEIC GE being a joint venture between Toshiba, Mitsubishi and GE.

Cblambert (talk) 22:58, 12 April 2012 (UTC)

What Bose has to say about power electtronics information is interesting:

• Key Books in Power Electronics
  • Bose, Mohan, Rashid, etc.
• IEEE Publications (ieeexplore.ieee.org)
• Individual Author Publication Websites , (scholar.google.com, scopus.com, etc.)
• Conference Records and Transactions – IAS, IES, PELS, PES, SES, APEC, PEDS/PEDES, CIEP – Mexico, etc.
• Proc. of the IEEE
• Conference Records of: EPE (Europe), ICEM, IPEC (Japan), PCC (Japan), PCIM, etc.
• Product Information in Key Power Electronic Company
• Websites:
  • ABB, GE, Fuji, Toshiba, Hitachi, Mitsubishi, Siemens, Rockwell, Samsung, etc.

Cblambert (talk) 21:20, 17 April 2012 (UTC)

Re: Basics of AC Drives

• Good review of, well, the basics. Copyrighted material

Re: Motoring Ahead

• Good stat to know about 30-40% VFDs and good article. ABB Review is evidently copyrighted material

Cblambert (talk) 15:15, 18 April 2012 (UTC)

Derivation of Ii = Tm.Nm/Ui; that is, AC current input to VFD is directly proportional to motor power

In case deletion of subject derivation should need to be restored, I have revised compared to last article version to read as follows:

"In principle, the inverter current and voltage outputs to the motor are respectively directly proportional to the motor torque and speed, whereas on the constant-voltage AC input to the VFD, the current is directly proportional to the power drawn by the motor. That is, neglecting VFD system losses and assuming unity power factor at AC input to VFD, U*I ~ T*N, where T = motor shaft torque, N = motor speed.

• i stands for AC line input to VFD, m for motor
• T stands for torque [Nm], U for voltage [V], I for current [A], N for speed [rad/s], PFm for motor power factor, and ~ for direct proportionality.

Neglecting losses assuming unity VFD input power factor, we have:

1. 1.732*Ui*Ii = 1.732*Um*Im*PFm (same 3-phase power drawn from VFD input as from VFD output)
2. Tm*Nm = 1.732*Um*Im*PFm (motor mechanical power = motor 3-phase electrical power)

Given that 1.732*Ui is a constant, Ii = Tm*Nm/1.732*Ui and Ii ~ Tm*Nm; that is, AC current input to VFD is directly proportional to motor power."

Derivation has not enough to do with VFD operation. Unity power factor assumption for VFD input is approximately true for diode rectifier drives but not active switching device VFD front ends. As stated, derivation is not really relevant.

Cblambert (talk) 18:21, 15 April 2012 (UTC)

Benchmarking VFD, motor and transformer article number of watchers

As a matter of interest, number of watchers of VFD article (~65) is about 4 times less than transformer and motor articles (each ~245). I don't know exactly what you make of this but others may have insights worth sharing.Cblambert (talk) 20:22, 18 April 2012 (UTC)

four quadrant control

added information on four quadrant control Shrikanthv (talk) 08:07, 19 April 2012 (UTC)

Electric motor speed-torque chart is incorrect:

• Quadrant I should read 'Motoring', not driving (VFD is drive, not a car)
• Quadrant III should read 'Reverse motoring/Regeration', not driving, (VFD is drive, not a car)

The image copies the same mistake as 'Basics of AC Drives' 4-quadrant speed-torque chart and is likely violation of copyright.Cblambert (talk) 20:18, 19 April 2012 (UTC)

Image should be labelled to match this text:

• Quadrant I - Motoring, forward accelerating quadrant with positive speed and torque
• Quadrant II - Generating, forward braking-decelleration quadrant with positive speed and negative torque
• Quadrant III - Motoring, reverse accelerating quadrant with negative speed and torque
• Quadrant IV - Generating, reverse braking-decellerating quadrant with negative speed and positive torque.

Cblambert (talk) 02:48, 20 April 2012 (UTC)

Some of the information regarding regeneration and braking were got from the links below , why are they being considered commercial links and being deleted ? please discuss

1) http://kimo.de/index.php?file=produkte/fu/u2/PB-TU2-06-08-22.html&menu=6&nav=1&lang=EN 2) http://kimo.de/index.php?file=anwend/kostenfu/PRO-Kosten-FU.html&lang=EN

It is true company related articles does contain wordings like , this is best suitable ... but i do believe information outwieghs the possible 'loss' Shrikanthv (talk) 08:09, 20 April 2012 (UTC)

We can use manufacturer's technical documents as sources for statements about the specific models they address. We cannot generalize from them to make statements about other manufacturer's products. This article is about variable-frequency drives in general not about any particular manufacturer's products.

The second source you list is a cost analysis. A manufacturer is not a reliable source for any generalized statements about economics or anything else about the industry. We need independent sources for such statements. Jojalozzo 15:29, 20 April 2012 (UTC)

I see you reverted the removal of the cost analysis link. It is inappropriate to make such changes before we have reached a conclusion on the talk page and I have removed that content again. Please leave it as it is while we are discussing it. We can restore it if and when there is general support for doing so.

In your edit summary you mentioned copyright violations. There would only be copyright violations if text were copied out of the source word for word or if the source were closely paraphrased. If that's the case it would not matter if the source were cited or not, it's still a violation. If that text is copied from the source we should reword the content in any case. Please explain. Jojalozzo 15:44, 20 April 2012 (UTC)

Little is accomplished by citing obscure, little known sources such as the one you refer to above hoping it will stick to the article wall. Can you respond to suggestion above regarding need for 4-quadrant image be labelled to match lastest revision of 'Drive Operation' section text?Cblambert (talk) 15:58, 20 April 2012 (UTC)

GAN nomination

The sourcing in this article needs some work. In particular there is one [citation needed] tag and some paragraphs have no citations at all. The citation style is also a bit confusing (why are there references linked on their own line below the headings. The multiple citations (although not strictly a criteria) could be reduced. A large number of citations following a sentence tend to suggest the presence of original research and make reading the prose difficult. AIRcorn (talk) 04:13, 17 May 2012 (UTC)

Original research inference is dead wrong. Read prior Talk discussions about controversies necessitating multiple citations to counter doubting Thomas arguments.Cblambert (talk) 05:23, 20 May 2012 (UTC)

GA Review

This review is transcluded from Talk:Variable-frequency drive/GA1. The edit link for this section can be used to add comments to the review.

Reviewer: Pyrotec (talk · contribs) 14:03, 17 May 2012 (UTC)

I will review. Pyrotec (talk) 14:03, 17 May 2012 (UTC)

Initial comments

I've had a quick read of the article and now I'm going to work my way through the article section by section, but leaving the WP:Lead until the end of the article.

On the basis of this quick reading, the article appears to have sufficient material to be considered for GA-status; but further improvements will be needed to obtain GA status this time round. For example: the current Lead is non-compliant with the requirements of WP:Lead since it is only provides an introduction for the article and makes no effort to summarise the main points. (I shall be covering this later in detail). There are also whole paragraphs, such as the first paragraph of Energy savings subsection of Benefits, that are unreferenced. The grammar/prose in some sentences is poor.

The article appears to have sufficient material to be considered for GA-status'

ExcellentCblambert (talk) 04:33, 20 May 2012 (UTC)

The requirements for GA can be found in WP:WIAGA, which is what I will be assessing the article against.

• System description and operation -

• There are two inconsistent types of referencing: ref 4 is "Jaeschke, pp. 210-211" and there is (an earlier) ref 2 a&b "Jaeschke, Ralph L. (1978). Controlling Power Transmission Systems. Cleveland, OH: Penton/IPC. pp. 210–215." I would argue that ref 4 could be combined with ref 2.
• Ref 5 is "NEMA Standards Publication (2007). Application Guide for AC Adjustable Speed Drive Systems. Rosslyn, VA USA: National Electrical Manufacturers Association (now The Association of Electrical Equipment and Medical Imaging Manufacturers). p. 4. Retrieved Mar. 27, 2008" and this is followed by ref 6, i.e. "NEMA, p. 13".
• Harvard-type citations should be made consistent. Using Jaeschke as an exmaple: "Jaeschke, Ralph L. (1978). Controlling Power Transmission Systems. Cleveland, OH: Penton/IPC." is quoted as a reference. Jaeschke, pp. 210-220 and Jaescke, pp. 210-210 are used a citations (possibly a poor example, as arguably the same reference could be used for all three occurrences).Pyrotec (talk) 18:13, 20 May 2012 (UTC)

My understanding is that first instance of reference is provided with full details with subsequent citations being in form 'last name (year/date), p. xxx).Cblambert (talk) 19:20, 20 May 2012 (UTC)

There is this Wikipedia:Citing sources, and if you wish to see a good example of a GA using that style try Leoš Janáček. Arguable this is Scientific article (well, engineering) so there is also Wikipedia:Scientific citation guidelines. Pyrotec (talk) 20:09, 20 May 2012 (UTC)

I have cleaned up citations to restore them to my current citation forma understanding in light of recent re-org of sections, which is my preference for now. Can go to Harvard format if need be. I have hesitated to make changes to old citations' pages because those old sources are in most cases not easy to access.Cblambert (talk) 01:47, 21 May 2012 (UTC)

• • Motor -

• A good, clear and well referenced paragraph. My only concern is that citation for the claims is NEMA Standard MG-1, which appears to be domestic USA standard. In Europe, where I am, we would be using EN, ISO or IEC standards. comment struck out. Pyrotec (talk) 20:09, 20 May 2012 (UTC)

This is why it says '. . . accordance to such requirements as Part 31 of NEMA Standard . . .' but I can see about European standard equivalent.Cblambert (talk) 17:46, 20 May 2012 (UTC)

Internet search for NEMA MG-1 Part 31 equivalent states in Eaton Application Note 'The Reflective Wave Phenomena' that ". . . 380V AC motors are typically European manufactured and have 1000V AC insulation. Therefore, the theoretical worst case voltage doubling effect is still within the capability of the insulation. Ergo, likely no equivalent European standard exists for NEMA MG-1 Part 31.Cblambert (talk) 18:48, 20 May 2012 (UTC)

Is the general statement "Elevated voltage stresses imposed on induction motors that are supplied by VFDs require that such motors be designed for definite-purpose inverter-fed duty " correct, i.e. can I use my existing (European) AC motor and just add a VFD drive, if I need a new motor and a drive I'll strike out this comment. Pyrotec (talk) 19:04, 20 May 2012 (UTC)

Not sure what you mean by 'strike out' but, yes, European general purpose low voltage motor can be used when adding a VFD drive.Cblambert (talk) 19:31, 20 May 2012 (UTC)

• • Controller -

• A repeat of a question I've asked below. What does "stiff" mean? Pyrotec (talk) 18:58, 20 May 2012 (UTC)
• See my comments above about citations/references.

... to be continued. Pyrotec (talk) 17:27, 20 May 2012 (UTC)

• Y Pyrotec (talk) 08:14, 22 May 2012 (UTC) - Citation 10, "Eisenbrown, Robert E. (May 18, 2008)" at the moment is coming up as a dead link - claimed to "Dead since 2012-04-28". Possibly, just removing the web link would (still) leave a valid citation; but a valid web link would be better.

Link removed. Cannot find link in Internet.Cblambert (talk) 22:37, 20 May 2012 (UTC)

• Y Pyrotec (talk) 08:14, 22 May 2012 (UTC) - "V/Hz drive control" is starting to appear in the text without any prior definition. I might assume that its shorthand for variable frequency drive(s), the title of the article being variable-frequency drive, which has an existing defined abbreviation of VFD (sometimes VF drive), also AFD and VSD. However, it is used as engineering unit: Volts per HZ.

In V/Hz control a VFD's voltage magnitude output is proportional to frequency or speed. V/Hz is also referred to as scalar control because there is only one controllable variable, say frequency or Hz with V being derived from actual Hz. V/Hz is suitable for low performance load application, which is most loads, i.e., centrifugal pumps, fans, compressors, etc. Trend however is for vector control or direct torque control due to trend to standarize on DSP-based microprocessors.Cblambert (talk) 22:37, 20 May 2012 (UTC)

Thanks for the explanation. Its first occurrence seems to be here: "In variable-torque applications suited for V/Hz drive control, AC motor characteristics require that ....". A minor change such as "In variable-torque applications suited for scalar control drives (V/Hz drive control), AC motor characteristics require that ..." would satisfy me. You don't have to do it this way, its merely one suggested approach. Pyrotec (talk) 10:40, 21 May 2012 (UTC)

• Y Pyrotec (talk) 08:32, 22 May 2012 (UTC) -I'm having trouble understanding: "In variable-torque applications suited for V/Hz drive control, AC motor characteristics require that the magnitude of the inverter voltage output to the motor be adjusted to match the required load torque with inverter frequency being derived from this voltage magnitude on a linear V/Hz relationship.".

At link as http://www3.sea.siemens.com/step/flash/STEPACDrives/index.htm, (Basics of AC Drives), go to part about 'AC Motors', slide 7 or 10 entitled "Motor Performance Under Load". You will see number of motor and load torque curves:

* One is a standard NEMA B type motor torque curve

* Two are variable torque load torque curves

A motor is designed to operate in the part of the motor torque curve to the right of the breakdown (i.e. highest) point of the curve, as one of the variable torque curve shows. (see in same 'AC Motors' part slides 4 and 5 for detailed treatment of NEMA B )

In order for this to happen, VFD inverter output voltage magnitude (and hence speed) must be adjusted to match the intersection of the two above torque curves.

See also in same 'Basics of AC Drives', part about 'AC Motors and Drives' slide 1 of 5 entitled 'Volts Per Hertz Ratio'.Cblambert (talk) 22:37, 20 May 2012 (UTC)

Thanks. It's the prose that I'm having problems with. Could it be written as (for instance): "In variable-torque applications suited for V/Hz drive control, the AC motor characteristics require that the magnitude of the inverter's output voltage supplied to the motor be adjusted to match the required load torque, such that there is linear (V/Hz) relationship between the inverter's frequency and output voltage."? (this is British English, I'm not too good at American English)? Pyrotec (talk) 10:40, 21 May 2012 (UTC)

•  Not done Pyrotec (talk) 11:27, 25 May 2012 (UTC) - I suspect that breakaway torque needs a definition or an explanation in brackets (braces).

• • Operator interface -

OK.

• • Drive operation -

• Y Pyrotec (talk) 11:46, 23 May 2012 (UTC) - Labelling between the chart and the first paragraphs is not consistent. The paragraph describes I & III as motoring and II & IV as Generation, but in the chart its Driving and braking. Possibly a minor difference in terminology, but it does stand out.

Labelling changed accordingly.Cblambert (talk) 22:12, 22 May 2012 (UTC)

• Benefits -
  • Energy savings -

•  Not done Pyrotec (talk) 11:27, 25 May 2012 (UTC) - The first paragraph makes a number of claims, but there are no references to support them.
• Y Pyrotec (talk) 15:45, 20 May 2012 (UTC) - Technical terms such as torque are used without explanation, they should be wikilinked on their first occurrence (I wikilinked horsepower).
• Y Pyrotec (talk) 15:45, 20 May 2012 (UTC) - The first paragraph appears to be confused. It starts talking about "variable speed drive"s, then it goes onto variable torque (twice), there are discussions of the relationships of torque, speed and horsepower, then it talks about speed and horsepower, and the relationships are named (the affinity laws). The second paragraph is mostly about variable torque, so perhaps the first was as well? The paragraph needs to be rewritten to improve readability.

• I did a couple of edits to improve the legibility. I hope that I've not changed the meaning. Pyrotec (talk) 15:45, 20 May 2012 (UTC)

•  Not done Pyrotec (talk) 11:27, 25 May 2012 (UTC) - References 6 and 8 are 44 and 132 pages long. The citations should therefore give the page number or numbers where "evidence" for the claimed statements can be found.

I have done editing accordingly. References can easily be provided.Cblambert (talk) 04:33, 20 May 2012 (UTC)

The reference numbers have changed due as a result of editing, ref 6 now appears to be ref 32 and ref 8 now 34. Pyrotec (talk) 11:27, 25 May 2012 (UTC)

... to be continued. Pyrotec (talk) 12:49, 19 May 2012 (UTC)

• • Control performance -

• Y Pyrotec (talk) 21:51, 20 May 2012 (UTC) - This whole subsection could do with a clean up. It is not clear what this subsection is about. Unless someone can explain what this stuff is here, I would be strongly tempted to fail the article on WP:WIAGA clause 3(a).

Most important benefit, for great majority of AC drives, is energy savings but AC drives inherently benefit in other ways including especially first sentence: 'AC drives are used to bring about process and quality improvements in industrial and commercial applications' acceleration, flow, monitoring, pressure, speed, temperature, tension and torque.'

• The subsection, unfortunately, looks much like a bullet-point list without bullet points. It consists of one single-sentence paragraph (1st paragraph), two two-sentence paragraphs (2nd & 4th) and one three-sentence paragraph (3rd). The first paragraph is badly written, but it seems to be about the benefits of AC drives. The second is unreferenced and appears to have a technical term (Across-the-line single-speed starters) that is not wikilinked or otherwise explained; it also appears to be comparing variable speed drives against AC motors that don't have them. The third is also unreferenced and appears to be comparing VFD's against what I assume is variable voltage drives (is reduced-voltage starting a drive?). The fourth paragraph gives a table comparing DC drives against what I assume is different types of AC drives, only one of which (AC V/Hz Control) appears to be a VFD. Since the Lead makes no mention of DC motors why are they here. Four-quadrant operation and hazardous area operation are technical terms that should be wikilinked or otherwise explained.

1st sentence re-written and sentence about 'reduced-voltage starting' has been deleted because largely redundant.Cblambert (talk) 04:33, 20 May 2012 (UTC)

Article would benefit from having a 'History' section to put things in perspective.Cblambert (talk) 04:33, 20 May 2012 (UTC)

'System description and operation' section moved to beginning of the article to ease in understanding of 'Benefits' and 'VFD Types and Ratings' sections.Cblambert (talk) 04:33, 20 May 2012 (UTC)

In 4th paragraph DC drive is compared to three AC drive/VFD control options.

• Y Pyrotec (talk) 21:51, 20 May 2012 (UTC) - Having looked at the table: AC V/HZ has the poorest speed regulation, it can't use a feedback device and it has the worst performance at zero/low speed and low speed constant torque operation. Its sole advantage is multiple motor operation. Am I right?

With all due respect, you are more or less wrong. In terms of performance:

* Speed regulation for DC drive and AC closed-loop (i.e., feedback) vector control drive is 100 time better than AC open-loop vector control drive

• Is a AC open-loop vector control drive a VFD? Where does it state that it is? Pyrotec (talk) 15:45, 20 May 2012 (UTC)

* Low end of speed range is infinity better for DC drive and closed-loop vector control AC drive than for the two open-loop AC drive options; in motion control/robotic application standstill is only game in town.Cblambert (talk) 04:33, 20 May 2012 (UTC)

• Is a AC closed-loop vector control drive a VFD? Where does it state that it is? Pyrotec (talk) 15:45, 20 May 2012 (UTC)

* It should really point out that V/Hz control is unsuitable for high-performance applications which can become unstable especially as low speed end of the range.Cblambert (talk) 04:33, 20 May 2012 (UTC)

In summary, beyond obvious benefit of soft starting, other control performance factor are crucial in many industrial applications.Cblambert (talk) 04:33, 20 May 2012 (UTC)

I will think further on the section and advise.Cblambert (talk) 04:33, 20 May 2012 (UTC)

It's my job to asses the nomination against WP:WIAGA. Considering clause 1 (a) "the prose is clear and concise, respects copyright laws, and the spelling and grammar are correct", it not clear what the drives labelled "AC V/Hz Control", "AC Open-Loop Vector", "AC Closed-Loop Flux Vector" are. The introduction to the table states; "The following table compares AC and DC drives according to certain key parameters", so one of the few things that is clear is that there is one DC and three AC drives in the table. I searched for "Flux vector" and "loop vector" and they only occur once in the article, and that is in this table. Its' not even clear that "AC V/Hz Control" is a VFD, I sort of assumed that it was. Let's have an unambiguous declaration in the table was to which AC drives are VFDs and which are not: as I said above "AC V/Hz Control" looked like it was a VFD simply because I recognised Hz as measure of frequency. Pyrotec (talk) 15:45, 20 May 2012 (UTC)

• Y Pyrotec (talk) 21:51, 20 May 2012 (UTC) - It simple to do, i.e.

Drive type	DC	VFD	VFD	VFD
Criteria	Brush Type DC	AC V/Hz Control	AC Open-Loop Vector	AC Closed-Loop Flux Vector
Typical speed regulation (%)	0.01	1	0.5	0.01
Typical speed range at constant torque	0-100	10-100	3-100	0-100
Min. speed at 100% torque (% of base)	Standstill	8%	2%	Standstill
Multiple-motor operation recommended	No	Yes	No	No
Fault protection (Fused only or inherent to drive)	Fused only	Inherent	Inherent	Inherent
Maintenance	(Brushes)	Low	Low	Low
Feedback device	Tachometer or encoder	N/A	N/A	Encoder

Done. Per article's 1st paragraph, last sentence,

Variable-frequency drives are also known as adjustable-frequency drives (AFD), variable-speed drives (VSD), AC drives, microdrives or inverter drives.,

it should be clear to you that the terms 'VFD' and 'AC drives' are used interchangeably.Cblambert (talk) 18:07, 20 May 2012 (UTC)

• VFD types and ratings -
  • Generic topologies -

• This subsection as written is not really acceptable as it stands. Much of it appears to be technobabble pretending to be explanation.

Technobabble!!?? Pretending!!?? I don't agree.

By all means disagree. The pass fail criteria is WP:WIAGA, so if I fail it, it will be against clause 1(a). I fail very few articles at WP:GAN (less than 10% of what I review), but I do fail articles. Pyrotec (talk) 16:05, 20 May 2012 (UTC)

Figure 1 from link at http://www05.abb.com/global/scot/scot239.nsf/veritydisplay/fec1a7b62d273351c12571b60056a0fd/$file/voltstress.pdf, "Principles of Operation for Variable Frequency Drives", provides good visualization relating AC drive topology elements with corresponding waveforms and functions. I will see about adding such treatment at beginning of 'System description and operation' section.Cblambert (talk) 19:04, 20 May 2012 (UTC)

• Y Pyrotec (talk) 16:05, 20 May 2012 (UTC) - The concept of Topology is not explained, but to me it seems to be how the AC is converted to DC and back to AC with an inverter (or not in one case). This should be stated explicitly. Note: the two figures for the VSI and CSI drives appear to show this diagrammatically. Very little is explained in English, not even DC is defined as Direct current (see the disambiguation page DC for instance). There is also one occurrence of D.C. in the Six-step inverter drives discussion. Is that the same as DC?

The concept of Topology has been explained.Cblambert (talk) 04:33, 20 May 2012 (UTC)

Article would benefit from having a 'History' section to put things in perspective.Cblambert (talk) 04:33, 20 May 2012 (UTC)

• Y Pyrotec (talk) 16:05, 20 May 2012 (UTC) - There are numerous technical terms such as: Diodes,capacitor and SCR-bridge, that are not wikilinked or even named. Darlington Pair is one exception that is wikilinked, but IGBT inverter, quasi-sinusoidal, stiff volatage and stiff quasi-sinusoidal appear without explanation nearby.

Wikilinks added where possible.Cblambert (talk) 04:33, 20 May 2012 (UTC)

Need to explain terms 'quasi' noted.

Y Pyrotec (talk) 10:43, 21 May 2012 (UTC) - "stiff" - does that mean the same as stiff in English, i.e. (1) not easily bent, (2) not relaxed/friendly, (3) strong, (4) full of, and if so which one? Pyrotec (talk) 16:05, 20 May 2012 (UTC)

...stopping for now. To be continued. Pyrotec (talk) 19:01, 19 May 2012 (UTC)

"Stiff" relates to electrical distribution system's (AC line power's) ability to not sag; in case of VFD, stiff relates to voltage in DC link capacitor's, or current in DC link inductor's, ability to not decay or sag when acted on by the inverter's motor load. Hence, why the two main inverter topologies are called voltage-source or current-source inverters. Has to do with circuit theory's Thévenin's theorem whereby ideal voltage and current sources behave as if there are 'infinite'(i.e., zero impedance) sources.Cblambert (talk) 17:12, 20 May 2012 (UTC)

The prefix term 'quasi-sinusoidal' implies 'close to sinusoidal'. A perfect inverter output is pure sine wave, which costs due to VFD rectification function's non-linearities. Older VFDs therefore used six-step, i.e., quasi-sinusoidal, inverter topologies, which in addition to the pure 'fundamental' sine wave component produced an infinite number of higher harmonic components. Some various small low performance VFDs even operate with square wave output, which can also be considered quasi-sinusoidal but is even higher in harmonic content.Cblambert (talk) 16:00, 21 May 2012 (UTC)

• Y Pyrotec (talk) 11:46, 23 May 2012 (UTC) - It was not obvious why six Generic topologies were dumped in this subsection without discussion; and for them to reappear in tables 1 and 2 without discussion. However, further discussion does appear later in the "Controller" subsection of System description and operation. It would be helpful to refer to this.

'System description and operation' section moved to beginning of the article to easy enhance understanding of 'Benefits' and 'VFD Types and Ratings' sections.Cblambert (talk) 04:33, 20 May 2012 (UTC)

Re tables 1 thru 4, this is admitedly a work in progess needing accompanying discussion.Cblambert (talk) 04:33, 20 May 2012 (UTC)

• • Control platforms & Load torque and power characteristics -

• Y Pyrotec (talk) 09:18, 22 May 2012 (UTC) - Again, I can't see the point of these subsections, as they are here without explanation.
• The first of these consists of a sentence with three bullet points and two see also's. "Control platforms" seems to only appear once again, as a single-sentence paragraph in "Controller" subsection of System description and operation.

Will think on this but this is intended as a summary of AC drive types.Cblambert (talk) 04:33, 20 May 2012 (UTC)

• Y Pyrotec (talk) 09:18, 22 May 2012 (UTC) - The second is an unreferenced sentence with three bullet points.

Will think on this but this is intended as a summary of AC drive types.Cblambert (talk) 04:33, 20 May 2012 (UTC)

...stopping for now. To be continued. Pyrotec (talk) 21:31, 19 May 2012 (UTC)

• • Available power ratings & Drives by machines & detailed topologies -

• OK.

• Application considerations -
  • AC line harmonics -

• Y Pyrotec (talk) 11:46, 23 May 2012 (UTC) - I suspect that "utility" (used three times in different paragraphs) is a USA term for the mains electricity supplier, we would probably call them power supply company, supplier, utility company. Its more obvious the second and third times what the term is being used for (substations and grid are the "clues" that clarify - I wikilinked both).

Changed accordingly to electrical power company in 1st instance and 'power company' in subsequent mention.Cblambert (talk) 22:12, 22 May 2012 (UTC)

• • AC line harmonics & Long lead effects -

• The second subsection starts off with "The output voltage of a PWM VFD consists of a train of pulses switched at what is called the carrier frequency." but carrier frequency is first discussed in the first subsection. I suggest that these two subsections be reviewed.

I have combined 1st two sentences of 'Long lead effects' in order to de-emphasize compard to 1st sentence in 'AC line harmonics'. AC line harmonics phenomena have to do with upsteam side of VFD whereas long lead effect phenomena have to do with downsteam side of VFD. Line harmonics are of relatively low frequencies compared to long lead effects. A big problem that PWM solved compared to older six-step inverter is PWM's ability to better approximate sine wave output to the motor. PWM thus allowed harmonic-free inverter output for frequencies below the carrier frequency. Which leave PWM drive with the two disctint problems:

Lower frequency harmonics on the AC line side of VFD

High frequency long lead effects on the motor side of the VFD.Cblambert (talk) 22:12, 22 May 2012 (UTC)

• Y Pyrotec (talk) 11:46, 23 May 2012 (UTC) - dv/dt filter needs a wikilink, explanation or description.

Changed accordingly.Cblambert (talk) 22:12, 22 May 2012 (UTC)

I made it into a footnote using the {{efn}} - three edits - this is not mandatory for GA, so you can undo it if you have objections. Pyrotec (talk) 12:05, 23 May 2012 (UTC)

• • Motor bearing currents -

• I'm not sure what those three citations are doing at the start of the subsection. The first paragraph is unreferenced as is the last one, so do they belong there?

I have repositioned two the three citations at the end of the paragraph. The remaining 'general' citation is still there because it is an old citation and I would have to dig back to see if it warrants keeping.Cblambert (talk) 22:12, 22 May 2012 (UTC)

That 3rd citation is in fact relevant to 1st sentence and has been positioned as such.Cblambert (talk) 16:37, 23 May 2012 (UTC)

• • Dynamic braking -

• The "slip" in "Torque generated by the drive causes the induction motor to run at synchronous speed less the slip" needs an explanation.

In first instance, I have noted 'slip' as being described in induction motor.Cblambert (talk) 22:12, 22 May 2012 (UTC)

• Y Pyrotec (talk) 12:24, 23 May 2012 (UTC) - That {{citation needed}} flag is rather obvious.

I had added a citation accordingly.Cblambert (talk) 22:12, 22 May 2012 (UTC)

• • Regenerative drives -

...stopping for now. Pyrotec (talk) 09:33, 22 May 2012 (UTC)

• WP:LEAD -

((tick|15}} Pyrotec (talk) 11:10, 25 May 2012 (UTC) - The function of the Lead is to both introduce the topic and to summarise the main points of the article. The current lead at 1.5 paragraphs is rather short. It does introduce the article but (in my opinion) is not all that good at summarising main points of the article.

I have no strong opinion on what is important (this is not my field), however, energy saving seems to be important. Different topologies, applications considerations could be important.

Possibly the current lead needs to be twice or three times as long (this is not a requirement just a hint at what I'm looking for), but only three (at most) four paragraphs long.

Pyrotec (talk) 12:24, 23 May 2012 (UTC)

Any comment on my kick at lead cat?Cblambert (talk) 16:50, 24 May 2012 (UTC)

I'm happy. Pyrotec (talk) 11:10, 25 May 2012 (UTC)

Overall summary

GA review – see WP:WIAGA for criteria

1. Is it reasonably well written?

   A. Prose quality:

   B. MoS compliance for lead, layout, words to watch, fiction, and lists:

   Yes, various edits during the course of this review have resulted in considerable improvements.

2. Is it factually accurate and verifiable?

   A. References to sources:

   B. Citation of reliable sources where necessary:

   Please note that there are two long citations 44 and 132 pages long. The relevant page number(s) have not been provided for these two reference publications

   C. No original research:

3. Is it broad in its coverage?

   A. Major aspects:

   B. Focused:

4. Is it neutral?

   Fair representation without bias:

5. Is it stable?

   No edit wars, etc:

I'm awarding this article GA status. Congratulations on producing what is now fine article. Pyrotec (talk) 11:37, 25 May 2012 (UTC)

2. Does it contain images to illustrate the topic?

   A. Images are copyright tagged, and non-free images have fair use rationales:

   Well illustrated.

   B. Images are provided where possible and appropriate, with suitable captions:

   Well illustrated.

3. Overall:

   Pass or Fail:

   In the light of the corrective actions that have been undertaken, I'm happy to award GA status.

I'm awarding this article GA status. Congratulations on producing, what is now, a fine article. Pyrotec (talk) 11:37, 25 May 2012 (UTC)

Rewriting lead according to wiki guidlines

I am going to rewrite lead section matching with wiki guidlines Shrikanthv (talk) 11:49, 24 May 2012 (UTC)

Can we have comments about lead from you reviewer and others?Cblambert (talk) 17:00, 24 May 2012 (UTC)

I could write a draft lead and paste it here, that that could lead to a conflict of interest. So I don't wish to do that. Are there any specific questions? If it helps: please remember that the lead is there as both as an introduction and to provide a summary of main points in the article. It should not "tease" by including material that is not in the article; and provided references are given for material in the body of the article the lead does not need to be separately referenced (unless its contentious). Pyrotec (talk) 17:51, 24 May 2012 (UTC)

I have no specific questions and away further comments about lead from all.Cblambert (talk) 19:19, 24 May 2012 (UTC)

Please check revert back on new edits on Lead section , hope it is now matching wiki guidlines Shrikanthv (talk) 11:05, 25 May 2012 (UTC)

Lead Reverts

Can we talk why the lead is being reverted back after getting GA ? , while the current (which was previous one ) did not match with GA guidlines Shrikanthv (talk) 15:31, 25 May 2012 (UTC)

I only made these minor edits which was mostly commas and full stops (or periods) and then awarded the article GA. The changes made since then do not invalidate its GA-status. Pyrotec (talk) 15:58, 25 May 2012 (UTC)

Stiffness - gloss

Good article - obviously lots of thought and time spent. However the "stiffness" query was never answered (Thévenin's theorem article has no mention). I concede that to anyone with any exposure to AC circuit theory it's an obvious metaphor, but we cannot assume that background. So I propose the following edit to the first appearances...stiff voltage [low impedance]...stiff current [high impedance]. Note the links to the Impedance article.Shannock9 (talk) 09:55, 26 August 2013 (UTC)

Query about tone?

Dup. of note posted to User talk:Cblambert (a user who has worked a lot on this page in the past) in case he/she is inactive.

I have a concern that I'm not knowledgeable enough to resolve.

Probably quite unintentionally by its authors, the article tone comes over (on the surface) to be generally skewed towards promoting these devices, or making them sound desirable or a significant opportunity, rather than merely factual info about that topic. For example -

• Introduction: VFDs' global market penetration... is still relatively small. That lack of penetration highlights significant ... opportunities
• Benefits: In the United States, an estimated 60-65% of electrical energy is used to supply motors ... Eighteen percent of the energy used in the 40 million motors in the U.S. could be saved by ... improvement technologies such as VFDs
• Benefits: Only about 3% of the total installed base of AC motors are provided with AC drives. However, it is estimated that drive technology is adopted in as many as 30-40% of all newly installed motors.
• At that point there's a table - but it's not of VFD's specifically, but of general motor installations (presumably to show VFD conversion opportunity?)

Perhaps these aspects of the topic can be better covered under a section "VFD market and adoption" - they are relevant to the topic, but placed as they are, it comes over as pushing this angle rather than providing encyclopedic coverage. FT2 ^{(Talk | email)} 07:20, 9 October 2015 (UTC)

Extremely confusing lead section

The lead section of this article is extremely difficult to fathom:

VFDs are used in applications ranging from small appliances to the largest of mine mill drives and compressors. However, around 25% of the world's electrical energy is consumed by electric motors in industrial applications, which are especially conducive for energy savings using VFDs in centrifugal load service,[5] and VFDs' global market penetration for all applications is still relatively small. That lack of penetration highlights significant energy efficiency improvement opportunities for retrofitted and new VFD installations.

I see no reason at all why the word "However" appears there, the term "centrifugal load service" seems to be very obscure, and the end of the paragraph seems disconnected from the beginning of it. NotYourFathersOldsmobile (talk) 02:11, 18 March 2016 (UTC)

GASP

VFD as in the volunteer fire department aaaaa jacques is dead — Preceding unsigned comment added by Plutonical (talk • contribs) 21:49, 7 April 2018 (UTC)