METHOD FOR REGULATION OF INDUCTION MOTOR ROTATION SPEED Russian patent published in 1997 - IPC

FIELD: low-speed electric motors. SUBSTANCE: method involves alternation of frequency of single- phase voltage which supplies stator winding of electric motor by means of application of control voltage to thyristors of commutator simultaneously to two thyristors of group of gates of commutator and one thyristor of another group of gates which are connected to three phases of stator winding of electric motor for time interval , where T is voltage period of power supply line, n is integer and is in range of 1-10. Then control voltage on one of two thyristors of group of commutator gates is switched off and simultaneously voltage is applied to thyristor of another group of commutator gates which is connected to same phase of stator winding of electric motor. This results in possibility shift vector of magnetic field by 60 electric degrees in direction of rotation. Shift speed is determined by used integer. EFFECT: possibility to control decreased rotation speed. 3 dwg