Static Rotor Resistance Control Methods

This method is used only for slip  ring induction motor in SRIM  3- phase  variable  resistor can be inserted in the rotor  circuit and by  varying this resistance in the rotor  circuit and by  varying this resistance  the motor  torque and hence speed  of th motor  can be  controlled. This methods  is  used when speed drop  is required for a short  time.

It has some  disadvantages if rotor  resistances are  not equal unbalances in voltages and  currents  occur at low  speeds efficiency is reduced and with  load variation speed  is changed very  quickly therefore  chopper circuit  is used.