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Vibration motor

A vibration motor is an electric motor driven by alternating current(AC) or Direct Current(DC) to produce the vibration in device. It usually consists of electric motor with attached unbalanced eccentric mass at the edges of motor driven shaft. The combination of both specific designed motor and the eccentric block enable the motor to rotate with vibration. It is designed in single phase and three phase supply.

Vibration motor has wide application in almost all types of industry to generate the vibration in operating device and knowingly as AC vibration motor for AC supply and DC Brushless vibration motor for DC supply.

Working principle of vibration motor

Vibration motor is essentially a motor that is unbalanced. In other words, there is an off centred counter weight attached to the motor rotational shaft that produce centrifugal force. Unbalanced force is transmitted to the vibration machine through the motor. The vibration frequency transmitted to the vibration machine can be determined by following formula :
f_v = (motor rpm)/60
F_V = m×r×ɯ²
where :
f_v is the vibration frequency
F_v is the vibration force
m is the mass of eccentric block
r is the mass offset distance
ɯ is the angular speed of motor in radian

Vibration machine frequency adjustment

As eccentric block at the edge of motor plays vital role to generate the vibration frequency for the vibration machine. Therefore, Frequency generated by the vibration motor can be adjusted in several way to control the vibration in vibration machine. The Most common ways are :

• By adjusting the eccentric weight - Vibration frequency is directly proportional to the mass of the eccentric weight. Frequency of vibration can be increased by increasing the weight of the block and can be decreased by decreasing the weight of the block.
  
• Using Voltage speed controller - Increasing the voltage supplied to the motor will increase the speed of motor. Hence vibration frequency is directly proportional to the speed of rotation motor will result in increasing the frequency as well as amplitude of vibration motor.
  
• Mass distance from the motor shaft - Bigger offset from the shaft will produce more force and hence more vibration amplitude will be transmitted to the vibration machine. Some time overheat of vibration motor also influence the frequency of vibration motor
  
• Angle between the centre of mass of eccentric weight and shaft centre axis - The angle between eccentric block will determine not only the direction of vibration and trajectory as well as determines the frequency of vibration machine. In case, both the eccentric block are symmetric about the plane intersecting the centre of electric motor and perpendicular to the shaft axis will generate the maximum force, frequency and amplitude.

Application of Vibration motor

There is vital application of vibration motor in industry. It is used almost in all industry to generate the vibration in vibration machine. Its very user friendly and without this its almost not possible to generate the heavy vibration. Here are the some industry where vibration motors are used :

1. Mines and Minerals industry
2. Coal Mines and construction industry
3. Chemicals andmedical
4. Food and agricultural machinery
5. Powder spraying equipment
6. Conveyors and grain machinery
7. Fire work machinery

Reference

• Electric motors and drives : Fundamental, Types and application 4th edition by Austin Hughes book Vibration motor
• Application of Vibration motor and specification
• Causes to an overheat of vibration motor
• Vibration motor frequency adjustment ways