Reswitching of an induction motor with remainder flux

The behaviour of the remainder flux of an induction motor after a short supply drop-out and the reswitching with a thyristor switch is presented. The initial value of the firing angle of the thyristors is dependent on the value of the voltage difference between the phase and induced voltage vectors, in amplitude and direction. To measure the voltage difference vector the three induced and supply phase voltages are transformed to a synchronous rotating two axis system. The time function of the firing angle is chosen to be a linear function, the final value of the firing angle will be the phase shift angle between voltage and current