Patent ID: 8544593

Claim:
A motor drive apparatus for driving a motor, which assists steering operation of a driver, the motor drive apparatus comprising: a DC power source; a plurality of inverters for converting electric power of the DC power source to AC power; a plurality of coil sets, provided in correspondence to the plurality of inverters, for driving the motor by currents supplied from the plurality of inverters; a failure detection circuit for detecting failure in the inverters or the coil sets by detecting currents flowing in the inverters or the coil sets; a power interruption section capable of interrupting power supply from the DC power source to the inverters; a torque sensor for detecting steering torque, by which a driver operates a steering wheel; and a control circuit for setting a command value of the current outputted from the inverter to the coil set and setting a current supply limitation value, which is an upper limitation value of the current command value, wherein, when the failure detection circuit detects the failure in any one of the inverters and the coil sets, the power supply interruption section interrupts power supply to the inverter that corresponds to the inverter or the coil set, which is detected as having failure, and the control circuit reduces the current supply limitation value for the inverter that is operating normally and other than the inverter, to which power supply is interrupted, and then increases the current supply limitation value for the inverter operating normally by a predetermined amount when a detection value of the steering torque detected by the torque sensor exceeds a predetermined threshold value.