Motor drive apparatus

A motor drive apparatus receiving electric power supplied from a DC power source and driving a motor that is provided with a plurality of independent polyphase systems of excitation coils, comprising:

• a control circuit and a plurality of power converters each corresponding to one of the systems, wherein
• each of the power converters includes an inverter circuit, an interrupter circuit connected between the inverter circuit and an excitation coil of a phase of the system, and a temperature detector,
• the inverter circuits are connected in series to the DC power source and, while not in a short-circuit mode, each inverter circuit supplies electric power to the excitation coil of a corresponding phase, and
• the control circuit detects an operating state of the motor, and switches the inverter circuits to the short-circuit mode and the interrupter circuits to an interruption mode, the inverter circuits and the interrupter circuits pertaining to a subset of the power converters defined according to the operating state of the motor, such that the control circuit causes a source voltage from the DC power source to be supplied to the inverter circuits that are not in the short-circuit mode, and, when a temperature detected for a given power converter by the temperature detector exceeds a predetermined temperature, the control circuit switches the inverter circuit of the given power converter to the short-circuit mode and switches the interrupter circuit of the given power converter to the interruption mode, and, in another power converter for which the temperature detected by the temperature detector does not exceed the predetermined temperature, switches the inverter circuit to an operation mode and switches the interrupter circuit to a connection mode.