Patent ID: 8169174

Claim:
A motor circuit, comprising: an alternating-current motor that includes first phase to n th phase coils; a motor drive control circuit that includes first phase to n th phase alternating-current feed lines through which an n-phase alternating-current is supplied to the alternating-current motor; and phase-open units that disconnect the motor drive control circuit and the alternating-current motor from each other in an abnormal condition where the n-phase alternating-current is not able to be output, wherein the first phase alternating-current feed line branches into paired branch feed lines; the first phase to n th phase coils are connected to each other in a ring-connection manner by arranging the first phase to n th phase coils, connected to each other in series, between the paired branch feed lines, and connecting the second phase to n th phase alternating-current feed lines to portions at which the phase coils are connected to each other in a serial connection circuit that includes the first phase to n th phase coils; the phase-open units are provided in the second phase to n th phase alternating-current feed lines and at least one of the branch feed lines; and when an electric current flows through the phase-open units when the abnormal condition occurs, the motor drive control circuit is configured to turn off each phase-open unit, where the electric current flows, after the electric current that flows through each phase-open unit becomes equal to or lower than a predetermined reference value determined by the motor drive control circuit.