Motor drive device

摘要

A motor drive device includes: an inverter circuit that has three switching elements corresponding to three phases of a three-phase motor coil, converts a DC applied voltage of a power source to an AC voltage by a PWM, and output the AC voltage to the motor coil; a voltage detection device for the DC applied voltage; and a control device that controls the PWM. The control device selects a first modulation method, for fixing the on/off-state of a part of the switching elements and for switching the on/off-state of the other part of the switching elements, or a second modulation method, for switching the on/off-state of the switching elements corresponding to three phases. The control device switches from the first modulation method to the second modulation method when the DC applied voltage is equal to or greater than a predetermined voltage, and the first modulation method is selected.

主权项

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.