Patent ID: 8054026

Claim:
A short circuit phase identification method by which a phase of a motor control device in which a short circuit has occurred is identified by a control signal of an inverter circuit that includes upper-stage and lower-stage transistors, which switch and supply an electric power to each phase of an alternating current motor installed on a vehicle, and a current of each phase detected by current detectors that detect an electric current supplied to each phase of the alternating current motor, the method comprising: a non-energized state determination process of determining whether each phase is non-energized when the alternative current motor is in a low-rotational speed state, based on the current detected in each phase; and a malfunction detection process of smoothing the detected current of each phase and determining whether the inverter circuit has malfunctioned if the non-energized state cannot be detected in the non-energized state determination process, based on a difference between a signal taking an absolute value of an electric current after the smoothing process and a signal obtained by smoothing an absolute value of the detected current of each phase, and also based on predetermined current levels of one-phase short circuit, two-phase short circuit, and three-phase short circuit.