Permanent magnet synchronous motor

Patent metadata

Field	Value
Publication number	US-11011965-B2
Application number	US-201515747879-A
Country	US
Kind code	B2
Filing date	Jul 31, 2015
Priority date	Jul 31, 2015
Publication date	May 18, 2021
Grant date	May 18, 2021

Abstract

A permanent magnet synchronous motor includes a stator, a rotor rotatable relative to the stator, and a magnetic structure with a low coercive force magnet and a high coercive force magnet that are arranged magnetically in series with respect to each other to define a pole-pair of the permanent magnet synchronous motor. A magnetization level of the low coercive force magnet is changeable by a stator current pulse such that a stator magnetomotive force at a rated current is equal to or larger than a product of a magnetic field strength for fully magnetizing the low coercive force magnet and a thickness of the low coercive force magnet.

First claim

What is claimed is:

1. A permanent magnet synchronous motor comprising:
a stator;
a rotor rotatable relative to the stator; and
a magnetic structure with a low coercive force magnet and a high coercive force magnet that are arranged magnetically in series with respect to each other to define a pole-pair of the permanent magnet synchronous motor,
a magnetization level of the low coercive force magnet being changeable by a stator current pulse, and
a rated current of the permanent magnet synchronous motor being set such that a stator magnetomotive force at the rated current is equal to or larger than a product of a magnetic field strength for fully magnetizing the low coercive force magnet and a thickness of the low coercive force magnet.

2. The permanent magnet synchronous motor according to claim 1 , wherein
the stator, the rotor and the magnetic structure are further configured to satisfy the following formula (1):

M
⁢

⁢
M
⁢

⁢
F

≥

H

M
⁢
ax

⁢

t
Low

-

J
High

μ
0

⁢

μ
rh

⁢

t
High

+

(

J
Max

μ
0

⁢

μ
rl

+

H
Max

)

⁢

(

t
High

+

t
g

)

(
1
)

where MMF represents the stator magnetomotive force per pole at the rated current, H Max represents the magnetic field strength for fully magnetizing the low coercive force magnet, t Low represents a thickness of the low coercive force magnet, J High represents a magnetization of the high coercive force magnet, μ 0 μ rh represents a magnetic permeability of the high coercive force magnet, μ 0 μ rh represents a magnetic permeability of the low coercive force magnet, t High represents a thickness of the high coercive force magnet, J Max represents a magnetization of the low coercive force magnet fully magnetized, and t g represents an air gap length between the stator and the rotor.

3. The permanent magnet synchronous motor according to claim 1 , wherein
the stator, the rotor and the magnetic structure are further configured to satisfy the following formula (2):

M
⁢

⁢
M
⁢

⁢
F

≥

-

H
Min

⁢

t
Low

+

J
High

μ
0

⁢

μ
rh

⁢

t
High

-

(

J
Min

μ
0

⁢

μ
rl

+

H
Min

)

⁢

Assignees

• Nissan Motor
• Wisconsin Alumni Res Found

Inventors

• Sasaki Kensuke
• Fukushige Takashi
• Katou Takashi
• Athavale Apoorva
• Lorenz Robert D

Classifications

• H02K1/276 Primary

  Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM] · CPC title

• H02K1/2781

  Magnets shaped to vary the mechanical air gap between the magnets and the stator · CPC title

• H02P25/28

  using magnetic devices with controllable degree of saturation, e.g. transductors · CPC title

• H02P9/123

  for demagnetising; for reducing effects of remanence · CPC title

• H02P6/08

  Arrangements for controlling the speed or torque of a single motor (H02P6/10, H02P6/28 take precedence) · CPC title