Permanent-magnet three-phase duplex motor and electric power steering apparatus
A permanent-magnet three-phase duplex motor is provided with two systems, namely a system that includes a first three-phase winding and a first inverter circuit, and a system that includes a second three-phase winding and a second inverter circuit, and a controlling apparatus is configured such that when one system fails, the controlling apparatus stops operation of the inverter circuit of the failed system, and controls operation of the inverter circuit of the normal system to increase the driving current that is supplied from the inverter circuit of the normal system, and the first three-phase winding and the second three-phase winding are configured such that magnetic fields that act on the permanent magnets in a demagnetizing direction when the increased driving current is supplied from the inverter circuit of the normal system are equal to magnetic fields that normally act on the permanent magnets in the demagnetizing direction.
1. 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 said driving current that is supplied from each of said first inverter circuit and said second inverter circuit to said first three-phase winding and said second three-phase winding during normal operation is set to a first electric current, and 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 two times said first electric current to increase said driving current that is supplied from said normal inverter circuit to increase the torque induced on the motor from the 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 driving current that is increased to two times said first electric current is supplied from said normal inverter circuit are identical to magnetic fields that normally act on said permanent magnets in said demagnetizing direction.
2. The permanent-magnet three-phase duplex motor according to claim 1 , wherein:
phase windings that constitute said first three-phase winding and said second three-phase winding are configured by connecting a plurality of unit coils that are each configured by winding a conductor wire into slots that are positioned on two sides of a plurality of contiguous teeth; and
circumferential regions between said slots into which said unit coils are wound that constitute same-phase phase windings of said first three-phase winding and said second three-phase winding overlap.
3. The permanent-magnet three-phase duplex motor according to claim 2 , wherein said first three-phase winding and said second three-phase winding are disposed so as to have a phase difference of thirty electrical degrees.
4. The permanent-magnet three-phase duplex motor according to claim 3 , wherein a number of poles in said rotor is eight, and a number of slots in said stator is forty-eight.
5. An electric power steering apparatus that comprises the permanent-magnet three-phase duplex motor according to claim 4 .
6. 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 to increase the torque induced on the motor from the 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,
wherein:
phase windings that constitute said first three-phase winding and said second three-phase winding are configured by connecting a plurality of concentrated winding coils that are each configured by winding a conductor wire onto a single tooth; and
said concentrated winding coils that constitute same-phase phase windings of said first three-phase winding and said second three-phase winding are wound onto identical teeth.
7. The permanent-magnet three-phase duplex motor according to claim 6 , wherein a number of poles in said rotor is ten, and a number of slots in said stator is twelve.
8. An electric power steering apparatus that comprises the permanent-magnet three-phase duplex motor according to claim 7 .