VARIABLE SPEED AC DRIVING DEVICE AND OPERATING METHOD

摘要

PURPOSE: To reduce a torque ripple over the whole range of a motor speed by operating an inverter bridge circuit, so that a multi-phase AC current with a shifted phase is generated in the windings of a plurality of sets of multi-phase motors. CONSTITUTION: A DC current obtained by converters 10, 11 flows into respective inverters 5, 6 through DC links 7, 8. The measured values of a link current Id1, Id2 are supplied to a control system 22 through an isolating circuit 24 together with six instantaneous values of a power source voltage. Furthermore, the phase angles θ1 , θ2 of magnetomotive force MMF which is generated from two sets of motor windings 3, 4 and measured by a synchronous generator 25 connected to a motor shaft are supplied to a control system. The control system 22 generates an ignition pulse sent to the thyristor of a multiple converter/inverter device by utilizing those measured values. The converters 10, 11 are controlled so as to generate a nearly constant DC current in the DC links 7, 8.