Inverter unit for driving ac motor

Abstract

Abstract PURPOSE:To spare a special motor with a neutral point for a load motor with a higher harmonic current generated on current control to be flowed to a 3rd phase, by subjecting 2 phases to a current control and the 3rd phase to a voltage control. CONSTITUTION:A current control circuit of 2 phases, an amplifier 30, a NOT circuit 33, an amplifier 36 and comparators 22, 23 are arranged. A respective output of comparators 22, 23 are input to an adding circuit 39 respectively through filters 37, 38 to obtain a voltage waveform A. Then an output thereof is input to a modulation circuit 40 (modulation wave triangle wave B) and modulated as shown in the figure C, and applied through the amplifier 30 and the NOT circuit 33 to electric valves 7, 8 to control them. That is, 2 phases are current-controlled so that a current of each phase coincides with each normal current waveform by an on-off state of each electric valve, and the remaining one phase is voltage-controlled according to a normal voltage waveform obtained by composing control signals of other phases by an on-off state of its electric valve.

Inventors

• 👤 Isamu Ukai

Bibliographic Details