Permanent-magnet three-phase duplex motor and electric power steering apparatus

A permanent-magnet three-phase duplex motor comprising:

• a rotor in which permanent magnets are arranged circumferentially;
• a stator that comprises a stator coil that is constituted by a first three-phase winding and a second three-phase winding;
• a first inverter circuit that supplies a driving current to said first three-phase winding;
• a second inverter circuit that supplies a driving current to said second three-phase winding;
• and
• a controlling apparatus that controls operation of said first inverter circuit and said second inverter circuit,
• wherein:
• said controlling apparatus is configured such that when one of said first inverter circuit and said second inverter circuit fails, said controlling apparatus stops operation of said failed inverter circuit, and controls operation of a normal inverter circuit to increase said driving current that is supplied from said normal inverter circuit;
• and
• said first three-phase winding and said second three-phase winding are configured such that magnetic fields that act on said permanent magnets in a demagnetizing direction when said increased driving current is supplied from said normal inverter circuit are equal to magnetic fields that normally act on said permanent magnets in said demagnetizing direction.