Study of start up for double squirrel-cage induction motor with discret frequency control

This paper presents an approach of the start up of double squirrel-cage induction motor by means of AC thyristors. Because wide range of spectral harmonics, it is believed that the single-cage model is not suitable to represent the behavior of squirrel-cage induction motors in dynamic studies. The mathematical model of a double cage induction machine is proposed. The developed model is studied when the motor is fed by classical soft starting control voltage and the technique of the discrete frequency control (DFC). Sub-harmonic frequencies have been generated permitting the starting of the induction machine under low frequencies such as 12.5 Hz, 16.66 Hz and 25 Hz. Using the proposed strategies of discrete frequency control, Simulation results have shown a current reduction along with significant starting torque improvement compared to soft starting method.