16 March 2017

Speed Control of Slip Ring Induction Motor By Chopper

  • The speed control of the slip ring induction motor by chopper is shown in the figure A. 
  • The ON and OFF time of chopper is adjusted in order to get desirable speed of the motor. 
  • The three phase rectifier converts ac into dc. 
  • The copper losses are very high due to high content of harmonics at the output of the rectifier.
  • The function of the inductor is to reduce ripple at the output of the rectifier.
  • When chopper CH is ON, the resistance R2 is short circuited. 
  • Similarly when the chopper CH is OFF, the external resistance is equal to R1 + R2. The average external resistance can vary by switching chopper.
Effective external resistance =
           R1 ( TON ) + ( R1 + R2 )( TON + TOFF ) / ( TON + TOFF )

  • The speed of the slip ring induction motor depends upon rotor resistance. The high speed operation of motor is obtained by low rotor resistance and vice versa. The speed of the motor can be changed by ON – OFF control of chopper.
  • The transistor is used as switching device for low power, GTO for medium power and SCR for high power requirement in the chopper circuit. 


speed control of slip ring induction motor by chopper


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