Patent ID: 8018195
Filing Date: 2011-09-13
Classification: H02M,H02P

Abstract:
1. An AC motor drive control device, comprising: a synchronous AC motor; an inverter; an overmodulation control unit that applies, via the inverter to the synchronous AC motor, a PWM (pulse width modulation) voltage which has a predetermined voltage amplitude and predetermined phase according to a torque command and in which the voltage amplitude exceeds a peak value of a reference triangle wave; a rectangular wave voltage phase control unit that controls a phase of a rectangular wave voltage which provides output of one pulse every half a period of an output voltage fundamental wave according to a torque command, and applies the controlled rectangular wave voltage via the inverter to the synchronous AC motor; a voltage amplitude calculator that calculates an amplitude of a voltage applied to the synchronous AC motor; a required voltage amplitude calculator that calculates a required voltage amplitude required by the synchronous AC motor; and a control mode judgment unit that performs a judgment to switch the unit for applying voltage to the synchronous AC motor from the rectangular wave voltage phase control unit to the overmodulation control unit when the required voltage amplitude becomes less than a value obtained by multiplying the peak value of the reference triangle wave by 1.27.