Patent ID: 9628004
Date: 2017-04-18
CPC Classifications: B60L,H02K,H02M,H02P,Y02T

Claim:
1. A motor drive device comprising: an inverter circuit that has three switching elements arranged so as to respectively correspond to three phases of a motor having a three-phase motor coil, converts a direct-current applied voltage applied from a power source to an alternating-current voltage by a pulse width modulation according to a switching operation for switching between an on-state and an off-state of each switching element, and output the alternating-current voltage to each phase of the motor coil; a voltage detection device that detects the direct-current applied voltage; a control device that controls the PWM of the inverter circuit, wherein: the control device selectively switches a PWM method between a first modulation method, for fixing the on-state and the off-state of the switching element corresponding to at least one of three phases and for switching the on-state and the off-state of the switching element corresponding to the other at least one of three phases, and a second modulation method, for switching the on-state and the off-state of the switching elements corresponding to three phases; and the control device switches the PWM method from the first modulation method to the second modulation method when the direct-current applied voltage detected by the voltage detection device is equal to or greater than a predetermined voltage under a condition that the first modulation method is selected; the second modulation method is a three-phase modulation method; and when the direct-current applied voltage is equal to or greater than the predetermined voltage, and the three-phase modulation method is selected, the control device executes the PWM with limiting an absolute value of a modulation factor to be less than a predetermined value.