Patent ID: 8410745

Claim:
A controller for a motor which is powered by a direct-current power source via a multi-phase inverter circuit composed of switch portions having switch elements and feedback diodes connected in parallel to the switch elements disposed at a positive polarity side and a negative polarity side of an arm of each phase, comprising: a short-circuit failure detecting member configured to detect an occurrence of a short-circuit failure which causes any switch portion in the inverter circuit to be in a continual conducted state during the operation of the motor; a short circuit failure polarity determining member configured to determine whether a short-circuit failure switch portion in which an occurrence of a short-circuit failure has been detected by the short-circuit failure detecting member is on the positive polarity side or on the negative polarity side; a short-circuit failure controlling member configured to control each of other switch element of the other switch portions except at least the short-circuit failure switch portion among the switch portions in the inverter circuit in such a way that a first group of the switch portions among the switch portions on the same polarity side as the short-circuit failure switch portion determined by the short-circuit failure polarity determining member are in a conducted state and the switch elements of a second group of the switch portions among the other switch portions on the different polarity side from the short-circuit failure switch portion are in a disconnected state; and a phase current detecting member configured to detect a phase current of each phase of the motor, wherein the short-circuit failure polarity determining member determines whether the short-circuit failure switch portion is on the positive polarity side or on the negative polarity side according to a direction of each phase current detected by the phase current detecting member after short-circuit failure polarity determining member has set a power source switch disposed in a power distribution path between the direct-current power source and the inverter circuit in the disconnected state and has output a control signal to all the switch elements in the inverter circuit to set the switch element in the disconnected state.