Motor circuit and electric power steering apparatus

A motor circuit, comprising:

• an alternating-current motor that includes first phase to nth phase coils;
• a motor drive control circuit that includes first phase to nth 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 nth phase coils are connected to each other in a ring-connection manner by arranging the first phase to nth phase coils, connected to each other in series, between the paired branch feed lines, and connecting the second phase to nth 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 nth phase coils;
• the phase-open units are provided in the second phase to nth 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.