Means to reduce harmonic torque in electromagnetic machines

• US 4,739,201 A
• Filed: 07/25/1986
• Issued: 04/19/1988
• Est. Priority Date: 07/25/1986
• Status: Expired due to Term

• Current Assignee: Dana Corporation (Dana, Inc.)
• Original Assignee: The Superior Electric Co.
• Inventors: Vivirito, Joseph R., Brigham, Robert N.
• Primary Examiner(s): Duggan, Donovan F.
• Application Number:
  US06/889,529
• Time in Patent Office: 634 Days
• Field of Search: 310/49, 310/112, 310/114, 310/162-165, 310/156
• US Class Current: 310/49.01
• CPC Class Codes: H02K 1/2713 the magnetisation axis of the magnets being axial, e.g. claw-pole type
• CPC Class Codes: H02K 37/18 of homopolar type

Abstract

An electromagnetic machine of the type having a moving member and a stationary member, with a set of structures on the moving member to magnetically interact with a set of structures on the stationary member, has an improved construction comprising displacing by an angle of displacement, α_m, from their normal positions, a first portion of one set of structures whereby the displacement causes a harmonic of the fundamental torque/angle curve to be attenuated. The angle of displacement is determined by the following relationship:

α.sub.m =α.sub.e /p,

where

α_e =displacement in electrical degrees,

p=number of moving member magnetic pole pairs,

further where α_e =180/h,

where h=an integer equal to the number of a harmonic of the fundamental torque/angle curve to be attenuated.

Claims

1. In an electromagnetic machine of the type having a moving member and a stationary member, with a set of structures on the moving member to magnetically interact with a set of structures on the stationary member, the improvement comprising displacing by an angle of displacement, α

_m, from their normal positions, a first portion of one set of structures from a second portion of that set of structures;

where;

space="preserve" listing-type="equation">α

.sub.m =α

.sub.e /p,

where

α

_e =displacement in electrical degrees,

p=number of moving member magnetic pole pairs,

further where

space="preserve" listing-type="equation">α

.sub.e =180/h,

where h=an integer equal to the number of a harmonic of the fundamental torque/angle curve to be attenuated.

2. An electromagnetic machine, as defined in claim 1, wherein:

(a) the moving member is a rotor; and

(b) the stationary member includes a set of poles radially disposed about the rotor.

12. The invention, as defined in any of claims 1 through 11, wherein the electromagnetic machine is a motor.

13. The invention, as defined in any of claims 1 through 11, wherein the electromagnetic machine is a generator.

3. An electromagnetic machine, comprising:

(a) a rotor having a cylindrical, axially-magnetized magnet with cylindrical pole pieces on the ends thereof, the pole pieces having equally-spaced longitudinal teeth formed on their peripheries, the teeth of one pole piece being radially displaced from the teeth on the other pole piece by one-half tooth pitch plus an angle, α

_m ;

(b) a set of stator poles radially disposed about the rotor to magnetically interact with the rotor; and

(c) where;

space="preserve" listing-type="equation">α

.sub.m =α

.sub.e /p,

where

α

_e =displacement in electrical degrees,

p=number of rotor magnetic pole pairs,

further where

space="preserve" listing-type="equation">α

.sub.e =180/h,

where h=an integer equal to the number of a harmonic of the fundamental torque/angle curve to be attenuated.

4. An electromagnetic machine, comprising:

(a) an untoothed rotor having a cylindrical, radially magnetized surface with two sets of alternate N and S magnetic poles displaced symmetrically thereon, the poles of one set being radially displaced from the poles of the other set, such that an N pole of one set is displaced from the corresponding N pole of the other set by one-half pole pitch plus an angle, α

_m ;

(b) a set of stator poles radially disposed about the rotor to magnetically interact with the rotor; and

(c) where;

space="preserve" listing-type="equation">α

.sub.m =α

.sub.e /p,

where α

_e =displacement in electrical degrees,

p=number of rotor magnetic pole pairs,

further where

space="preserve" listing-type="equation">α

.sub.e =180/h,

where h=an integer equal to the number of a harmonic of the fundamental torque/angle curve to be attenuated.

5. An electromagnetic machine, comprising:

(a) a rotor having two axially-aligned, axially-magnetized, cylindrical magnets, each having a cylindrical pole piece on each end thereof, the magnets and pole pieces being in axial alignment, the pole pieces having uniform and equally-spaced teeth on their peripheries, the teeth of one pole piece on each magnet being displaced from the teeth of the other pole piece on each magnet by one-half tooth pitch, and the teeth of the pole pieces on one magnet being radially displaced from the teeth of the corresponding pole pieces on the other magnet by an angle, α

_m ;

(b) a set of stator poles radially disposed about the rotor to magnetically interact with the rotor; and

(c) where;

space="preserve" listing-type="equation">α

.sub.m =α

.sub.e /p,

where α

_e =displacement in electrical degrees,

p=number of rotor magnetic pole pairs,

further where

space="preserve" listing-type="equation">α

.sub.e =180/h,

where h=an integer equal to the number of a harmonic of the fundamental torque/angle curve to be attenuated.

6. An electromagnetic machine, comprising:

(a) a toothed, axially-magnetized rotor;

(b) a set of stator poles radially disposed about the rotor to magnetically interact with the rotor, the stator poles being axially divided into two sections, with one section being radially displaced from the other section by one-half a rotor tooth pitch plus an angle, α

_m ; and

(c) where;

space="preserve" listing-type="equation">α

.sub.m =α

.sub.e /p,

where α

_e =displacement in electrical degrees,

p=number of rotor magnetic pole pairs,

further where

space="preserve" listing-type="equation">α

.sub.e =180/h,

where h=an integer equal to the number of a harmonic of the fundamental torque/angle curve to be attenuated.

7. An electromagnetic machine, comprising:

(a) a toothed, axially-magnetized rotor;

(b) a set of stator poles radially disposed about the rotor to magnetically interact with the rotor, the stator poles having teeth on the surface facing the rotor, the stator poles being axially divided into sections, and the teeth on one section being radially displaced from the teeth on the other section by one-half a rotor tooth pitch plus an angle α

_m ; and

(c) where;

space="preserve" listing-type="equation">α

.sub.m =α

.sub.e /p,

where

α

_e =displacement in electrical degrees,

p=number of rotor magnetic pole pairs,

further where

space="preserve" listing-type="equation">α

.sub.e =180/h,

where h=an integer equal to the number of a harmonic of the fundamental torque/angle curve to be attenuated.

8. An electromagnetic machine, comprising:

(a) a rotor having a cylindrical, axially-magnetized magnet with cylindrical pole pieces on the ends thereof, the pole pieces having equally-spaced longitudinal teeth formed on their peripheries, the teeth of one pole piece being radially displaced from the teeth on the other pole piece by one-half tooth pitch minus an angle, α

_m ;

(b) a set of stator poles radially disposed about the rotor to magnetically interact with the rotor; and

(c) where;

space="preserve" listing-type="equation">α

.sub.m =α

.sub.e /p,

where α

_e =displacement in electrical degrees,

p=number of rotor magnetic pole pairs,

further where

space="preserve" listing-type="equation">α

.sub.e =180/h,

where h=an integer equal to the number of a harmonic of the fundamental torque/angle curve to be attenuated.

9. An electromagnetic machine, comprising:

(a) an untoothed rotor having a cylindrical, radially magnetized surface with two sets of alternate N and S magnetic poles displaced symmetrically thereon, the poles of one set being radially displaced from the poles of the other set, such that an N pole of one set is radially displaced from the corresponding N pole of the other set by one-half pole pitch minus an angle, α

_m ;

(b) a set of stator poles radially disposed about the rotor to magnetically interact with the rotor; and

(c) where;

space="preserve" listing-type="equation">α

.sub.m =α

.sub.e /p,

where α

_e =displacement in electrical degrees,

p=number of rotor magnetic pole pairs,

further where

space="preserve" listing-type="equation">α

.sub.e =180/h,

where h=an integer equal to the number of a harmonic of the fundamental torque/angle curve to be attenuated.

10. An electromagnetic machine, comprising:

(a) a toothed, axially-magnetized rotor;

(b) a set of stator poles radially disposed about the rotor to magnetically interact with the rotor, the stator poles being axially divided into two sections, with one section being radially displaced from the other section by one-half a rotor tooth pitch minus an angle, α

_m ; and

(c) where;

space="preserve" listing-type="equation">α

.sub.m =α

.sub.e /p,

where α

_e =displacement in electrical degrees,

p=number of rotor magnetic pole pairs,

further where

space="preserve" listing-type="equation">α

.sub.e =180/h,

where h=an integer equal to the number of a harmonic of the fundamental torque/angle curve to be attenuated.

11. An electromagnetic machine, comprising:

(a) a toothed, axially-magnetized rotor;

(b) a set of stator poles radially disposed about the rotor to magnetically interact with the rotor, the stator poles having teeth on the surface facing the rotor, the stator poles being axially divided into sections, and the teeth on one section being displaced from the teeth on the other section by one-half a rotor tooth pitch minus an angle, α

_m ; and

(c) where;

space="preserve" listing-type="equation">α

.sub.m =α

.sub.e /p,

where α

_e =displacement in electrical degrees,

p=number of rotor magnetic pole pairs,

further where

space="preserve" listing-type="equation">α

.sub.e =180/h,

where h=an integer equal to the number of a harmonic of the fundamental torque/angle curve to be attenuated.