Patent ID: 8674575
Filing Date: 2014-03-18
Classification: H02K

Abstract:
1. A permanent magnet electric motor comprising: a plurality of magnetic poles formed by using two types of permanent magnets, a product of coercivity and thickness in a magnetization direction of permanent magnets of a first type being smaller than that of permanent magnets of a second type; a rotor formed by locating the plurality of the magnetic poles inside a rotor core; a stator located outside the rotor, the rotor and the stator having an air gap intervening therebetween; and an armature core and an armature coil provided with the stator, wherein at least one permanent magnet with the smaller product of the permanent magnets configuring each of the plurality of magnetic poles of the rotor is magnetized by a magnetic field generated by an armature current of the armature coil so as to irreversibly change an amount of magnetic flux of the at least one permanent magnet, and a short circuit coil is located on the periphery of a first selected one of the permanent magnets excluding the permanent magnets of the second type so as to have an axis extending in a magnetization direction of the first selected one of the permanent magnets as a center axis of the short circuit coil, wherein the magnetic field generated by the armature current of the armature coil induces a short circuit current in the short circuit coil, the short circuit current generating a magnetic field that has a direction which is opposite from the direction of the magnetic field generated by the armature current on the first selected one of the permanent magnets and is the same as the direction of the magnetic field generated by the armature coil on the at least one permanent magnet with the smaller product.