# US 2014/0191628 A1 · Permanent magnet motor

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- Number: US 2014/0191628 A1
- Document ID: US20140191628A1
- Status: Published application
- Kind: A1
- Application number: 14/239,968
- Filed: 2011-12-23
- Published: 2014-07-10
- Earliest claimed: 2011-12-23
- Assignees: Mitsubishi Electric Corporation
- Inventors: Masatsugu Nakano; Yoshihito Asao; Satoru Akutsu; Ryuichi Takiguchi; Yuji Takizawa; Yu Hirotani
- Web page: https://patentgrep.com/patent/US20140191628A1

## CPC

- H02K 3/28: Layout of windings or of connections between windings (windings for pole-changing H02K17/06, H02K17/14, H02K19/12, H02K19/32)
- H02K 1/2746: the rotor consisting of magnets arranged with the same polarity, e.g. consequent pole type
- H02K 1/276: Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM]
- H02K 1/2773: {consisting of tangentially magnetized radial magnets}
- H02K 1/2781: Magnets shaped to vary the mechanical air gap between the magnets and the stator
- H02K 3/12: arranged in slots
- H02K 11/225: Detecting coils
- H02K 1/246: {Variable reluctance rotors}
- H02K 29/08: using magnetic effect devices, e.g. Hall-plates, magneto-resistors (H02K29/12 takes precedence)
- H02K 29/12: using detecting coils {using the machine windings as detecting coil}
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})

## Abstract

A permanent magnet motor in which electromagnetic excitation force of low spatial order is reduced, and influence of a magnetomotive force harmonic of a rotor and torque ripple is reduced. One set of armature windings receives current from a first inverter, and another set of armature windings receives current from a second inverter. Where a pole number of a rotor is M and the number of slots of a stator core is Q, M and Q satisfy M<Q and a greatest common divisor of M and Q is equal to or greater than 3. In the rotor, the iron core is located beyond a radius intermediate the maximum outer radius and the minimum inner radius of the permanent magnets. A phase difference between three-phase currents from the first and second inverters is in a range of electrical angles of 20 to 40 degrees.

## Claims

### Claim 1

A permanent magnet motor comprising:
a rotor including a rotor iron core and a plurality of permanent magnets provided in the rotor iron core; and
a stator including a stator iron core and two sets of three-phase armature windings provided in a plurality of slots formed in the stator iron core, wherein
one set of the armature windings is supplied with current from a first inverter, and the other set of the armature windings is supplied with current from a second inverter,
in the case where a pole number of the rotor is M and a slot number of the stator iron core is Q, M and Q satisfy a relationship of M<Q and a greatest common divisor of M and Q is equal to or greater than 3,
in the rotor, the rotor iron core is located on the stator side beyond a radius intermediate between the maximum outer radius and the minimum inner radius of the permanent magnets, and
a phase difference between three-phase currents supplied from the first inverter and three-phase currents supplied from the second inverter is controlled to fall within a range of electrical angles of 20 to 40 degrees.

### Claim 2 (depends on 1)

The permanent magnet motor according to claim 1, wherein the armature windings are wound in a distributed manner, a value of Q/(3M) which is a slot number for each pole for each phase is an integer, and further, the value of Q/(3M) is an even number equal to or greater than 2.

### Claim 3 (depends on 1)

The permanent magnet motor according to claim 1, wherein the permanent magnets have a planar shape.

### Claim 4 (depends on 1)

The permanent magnet motor according to claim 1, wherein the permanent magnets are embedded in the rotor iron core.

### Claim 5 (depends on 1)

The permanent magnet motor according to claim 1, wherein the permanent magnets have a shape in which a length thereof in a radial direction is greater than a length thereof in a circumferential direction, and are embedded in the rotor iron core.

### Claim 6 (depends on 1)

The permanent magnet motor according to claim 1, wherein
the permanent magnets have a rectangular sectional shape in which a length thereof in a radius direction is longer than a length thereof in a circumferential direction,
magnetization directions of the permanent magnets are set such that surfaces facing to each other of the adjacent permanent magnets have the same pole,
the rotor iron core is interposed between the adjacent permanent magnets, and a surface of the rotor iron core facing to the stator side is formed into a curved surface portion having such a convex shape that a gap length from the stator is shortened toward a midpoint between the adjacent permanent magnets, and
a non-magnetic portion is provided in contact with an end surface of each permanent magnet on an inner circumferential side.

### Claim 7 (depends on 1)

The permanent magnet motor according to claim 1, wherein the armature windings are wound in a concentrated manner, a protruding portion made of magnetic material is present between the adjacent permanent magnets of the rotor, and an outer side of the protruding portion in a radial direction protrudes toward the stator side beyond a radius intermediate between the maximum outer radius and the minimum inner radius of the permanent magnets.

### Claim 8 (depends on 1)

The permanent magnet motor according to claim 1, wherein a M/2 number of the permanent magnets are arranged along the circumferential direction of the rotor, where M is the pole number of the rotor.

### Claim 9 (depends on 1)

The permanent magnet motor according to claim 1, wherein a M/2 number of the permanent magnets are arranged along the circumferential direction of the rotor, where M is the pole number of the rotor, and are provided at a surface of the rotor iron core.

### Claim 10 (depends on 1)

The permanent magnet motor according to claim 1, wherein a M/2 number of the permanent magnets are arranged along the circumferential direction of the rotor, where M is the pole number of the rotor, and are embedded in the rotor iron core.

### Claim 11 (depends on 10)

The permanent magnet motor according to claim 10, wherein slits formed symmetrically with respect to a magnetic pole center of the rotor are provided in the rotor iron core.

### Claim 12 (depends on 1)

The permanent magnet motor according to claim 1, wherein
a M/2 number of the permanent magnets are arranged along the circumferential direction of the rotor, where M is the pole number of the rotor, and
the permanent magnets have a rectangular sectional shape in which a length thereof in a radial direction is greater than a length thereof in a circumferential direction, and are embedded in the rotor iron core.

### Claim 13 (depends on 1)

The permanent magnet motor according to claim 1, wherein
a M/2 number of the permanent magnets are arranged along the circumferential direction of the rotor, where M is the pole number of the rotor, and the permanent magnets have a rectangular sectional shape in which a length thereof in a radius direction is longer than a length thereof in a circumferential direction,
magnetization directions of the permanent magnets are set such that surfaces facing to each other of the adjacent permanent magnets have the same pole,
the rotor iron core is interposed between the adjacent permanent magnets, and
a non-magnetic portion is provided in contact with an end surface of each permanent magnet on an inner circumferential side.

### Claim 14 (depends on 12)

The permanent magnet motor according to claim 12, wherein slits formed symmetrically with respect to a center line of each permanent magnet are provided in the rotor iron core.

### Claim 15 (depends on 12)

The permanent magnet motor according to claim 12, wherein
the rotor iron core in the vicinity of a portion corresponding to an N pole and a portion corresponding to an S pole of the rotor iron core, which are formed in accordance with the magnetization directions of the permanent magnets, is formed in a shape not being rotationally symmetric, and
a surface of the rotor iron core has a curved-plane shape symmetric with respect to a center line of each permanent magnet.

### Claim 16 (depends on 1)

The permanent magnet motor according to claim 1, wherein a phase difference between three-phase currents supplied from the first inverter and three-phase currents supplied from the second inverter is controlled to be an electrical angle of 30 degrees.

### Claim 17 (depends on 5)

The permanent magnet motor according to claim 5, wherein a residual magnetic flux density of each permanent magnet is equal to or smaller than 1 T.

### Claim 18 (depends on 1)

An electric power steering apparatus comprising the permanent magnet motor according to claim 1.

### Claim 19 (depends on 1)

A permanent magnet motor for electric power steering apparatus, in which an ECU (control unit) is integrally provided in back of the permanent magnet motor according to claim 1, wherein
a sensor with a shaft angle multiplier of 1× is used for a rotational angle sensor of the motor, and
a pole pair number of the motor is equal to or greater than 3.

### Claim 20 (depends on 1)

A permanent magnet motor for electric power steering apparatus, in which an ECU (control unit) is integrally provided in back of the permanent magnet motor according to claim 1, wherein
a VR resolver with a shaft angle multiplier of NX is used for a rotational angle sensor of the motor, and
a pole pair number N of the motor is equal to or greater than 3.