INDUCTION MOTOR SPEED CONTROL METHOD Russian patent published in 2000 - IPC

FIELD: variable- speed induction-motor drives. SUBSTANCE: motor supply frequency is varied by applying control-voltage pulses to thyristors of three reversing converters. Pulses are fed to rectifier bridges of converters in turn, as follows: first to thyristors of first bridge, then in certain time interval equal to one sixth of supply voltage cycle, to those of second bridge, and after that, to thyristors of third bridge, also in certain time interval. The cycle is then repeated. Control-voltage pulses are synchronously fed to six thyristors of three inverter bridges of converters as follows: to three thyristors of valve anode groups connected to one phase winding of motor and to three thyristors of motor cathode groups connected to other phase winding of motor. In mentioned time interval supply of pulses to thyristors of one group of inverter-bridge valves is ceased and at the same time they are applied to other thyristors of same group of valves connected to other winding of motor. Then the cycle is repeated. EFFECT: enlarged speed control range. 3 dwg