Permanent-magnet-type rotating electrical machine
The present invention provides a permanent-magnet-type rotating electrical machine capable of realizing variable-speed operation in a wide range from low speed to high speed at high output and improving, in a wide operating range, efficiency, reliability, and productivity. A narrow magnetic path 11 is formed in a rotor core 2 of a rotor 1 at an inter-pole yoke that magnetically connects adjacent pole core portions 7 to each other, so that the narrow magnetic path is magnetically saturated with flux of a magnetic field created by a predetermined magnetizing current passed to an armature coil 21 . Each of first permanent magnets 3 at each of the pole core portions 7 is magnetized with a magnetic field created by a magnetizing current passed to the armature coil 21 , to irreversibly change the flux amount of the first permanent magnet.
1. A permanent-magnet-type rotating electrical machine comprising:
a rotor having a plurality of first permanent magnets embedded in a cylindrical rotor core at equiangular intervals in a rotation direction, each of the first permanent magnets having a product of coercive force and magnetizing direction thickness smaller than that of a second permanent magnet and being oriented so that a magnetizing direction thereof is orthogonal to a diametral direction or in a diametral direction and a plurality of the second permanent magnets embedded in the rotor core at equiangular intervals in the rotation direction, each of the second permanent magnets having a product of coercive force and magnetizing direction thickness larger than that of the first permanent magnet, being oriented so that a magnetizing direction thereof agrees with a diametral direction, and being positioned between adjacent ones of the first permanent magnets so that the adjacent first permanent magnets and the second permanent magnet between them form a magnetic pole, the number of the magnetic poles being equal to the number of the second permanent magnets;
a stator arranged to surround the rotor with a magnetic air gap interposing between them; and
an armature coil formed on an inner circumferential part of the stator that faces the magnetic air gap,
a narrow magnetic path being formed in the rotor core at an inter-pole yoke that magnetically connects adjacent ones of the magnetic poles to each other, so that the narrow magnetic path is magnetically saturated with flux of a magnetic field created by a predetermined magnetizing current passed to the armature coil,
each of the plurality of first permanent magnets at each of the plurality of magnetic poles being magnetized with a magnetic field created by a magnetizing current passed to the armature coil, to irreversibly change the flux amount of the first permanent magnet.
2. The permanent-magnet-type rotating electrical machine of claim 1 , wherein:
the rotor being configured such that the plurality of first permanent magnets are oriented in a direction in which a magnetizing direction thereof is orthogonal to a diametral direction and are embedded in the rotor at equiangular intervals in a rotation direction.
3. The permanent-magnet-type rotating electrical machine of claim 1 , wherein:
the narrow magnetic path at the inter-pole yoke of the rotor core is set so that it has a flux density of just before magnetic saturation if a maximum torque generating flux state is established in the permanent-magnet-type rotating electrical machine, so that it has a flux density of around magnetic saturation if a magnetizing current passed to the armature coil is zeroed, so that it is magnetically saturated when a magnetizing current is passed to the armature coil, so that its flux density at the zero current is larger than that at the maximum torque, and so that its flux density when the magnetizing current is passed is the largest.
4. The permanent-magnet-type rotating electrical machine of claim 1 , wherein:
a magnetic path sectional area at the inter-pole yoke of the rotor core is narrower than a magnetic path sectional area of a pole yoke on an inner side of a magnetic pole so that the narrow magnetic path is magnetically saturated with flux of the magnetic field created by the predetermined magnetizing current passed to the armature coil.
5. The permanent-magnet-type rotating electrical machine of claim 1 , wherein:
the inter-pole yoke of the rotor core has an average flux density of magnetic saturation and the pole yoke has an average flux density of before saturation.