Voltage Control of the Three-Phase Induction Motor by Thyristor Switching: a Time-Domain Analysis Using the α--β--0 Transformation

Phase-controlled thyristors connected back-to-back can be used to control the speed of induction motors. The motor windings carry a discontinuous pattern of current. The extinction angle of the thyristors is a function of the firing angle and the motor parameters. The α--β--0 transformation has been used to obtain a complete solution of the voltage equations for a constant speed of the motor. An approximate solution as well as the experimental results are presented.