Abstract: A method of eliminating self-oscillations of an induction motor powered from a thyristor frequency changer, differing from those known in the prior art in that it provides for forming a signal proportional to a first derivative of the low frequency component of the motor reactive current oscillations which signal is applied as a positive feedback, in sequence with a main control, signal to an output frequency control circuit of the thyristor frequency changer.A control system provided comprising a power supply and a power circuit energized by the former to produce an a.c. output voltage whose amplitude and frequency are proportionally regulated, and a control circuit energized by the power supply to control the power circuit. The latter circuit includes a three-phase rectifier bridge and an independent inverter. The control circuit includes respective means for controlling the amplitude and the frequency of the inverter output voltage.