Rotor Chopper Control for Induction Motor Drive: TRC Strategy

A solid-state induction motor speed regulating scheme using a rotor chopper-controlled external resistor is investigated. This control scheme provides continuous and contactless variation of rotor resistance and thereby eliminates the undesirable features of the conventional rotor resistance control method. A thorough analysis of the steady-state performance of the system is presented. Both dc and ac circuit models are derived to describe the performance characteristics when the chopper operates under the time-ratio control (TRC) strategy. Effects of machine parameters on performance characteristics are studied. Theoretical results from the model are verified by comparison with experimental results. The torque¿speed characteristic of this speed control system is essentially linear for a particular time ratio.