GB2139823A - Stator for an electromagnetic machine - Google Patents
Stator for an electromagnetic machine Download PDFInfo
- Publication number
- GB2139823A GB2139823A GB08410979A GB8410979A GB2139823A GB 2139823 A GB2139823 A GB 2139823A GB 08410979 A GB08410979 A GB 08410979A GB 8410979 A GB8410979 A GB 8410979A GB 2139823 A GB2139823 A GB 2139823A
- Authority
- GB
- United Kingdom
- Prior art keywords
- pole pieces
- stator
- radially
- cross
- section
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
- H02K21/12—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets
- H02K21/24—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets with magnets axially facing the armatures, e.g. hub-type cycle dynamos
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
- H02K1/12—Stationary parts of the magnetic circuit
- H02K1/14—Stator cores with salient poles
- H02K1/145—Stator cores with salient poles having an annular coil, e.g. of the claw-pole type
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Permanent Field Magnets Of Synchronous Machinery (AREA)
Abstract
Electromagnetic machines of the type having circular arrays of permanent magnets (3 Fig. 1) arranged on a rotor (2) and a plurality of pole pieces 6 arranged on a stator (1), requires that a maximum number of pole pieces be arranged around the stator in order to attain maximum utilization of the magnetic flux. The instant stator of an electromagnetic machine includes a plurality of U-shaped pole pieces 6 with adjacent ones of the pole pieces opening in opposite radial directions from an axis of the stator. The pole pieces 6a which open radially inwardly are stepped so as to have a relatively thicker portion 8 radially outwardly and a relatively thinner portion 9 radially inwardly. <IMAGE>
Description
SPECIFICATION
Stator for an electromagnetic machine
This invention relates generally to electromagnetic machines, and more particularly, to pole pieces for
motors having permanent magnet excitation.
There are, currently available, motors having circular arrays of permanent magnets arranged on a
rotor. The rotor is associated with a stator having a
plurality of pole pieces energized by a coil carrying a
controlled electric current. Commutation of the
electric current produces a rotating magnetic field in the stator, and interaction between the pole pieces
and the permanent magnets results in rotation of the
rotor. One example of such a motor is described in G B-A-1 541211.
In designing motors of this general type, it is
important to maintain the mutual inductance of the
coil at the lowest possible level in order to obtain
maximum utlization of the available magnetic flux,
increasing the efficiency of operation and decreasing
energy losses. Location and design of the pole
pieces is a critical factor in maximizing the utilization
of the magnetic flux. It is important that as many
pole pieces as possible be arranged around the
stator coil. Coincidentally, interpole magnetic flux
leakage needs to be kept as low as possible to
reduce leakage inductance.
GB-A-2006540 proposes staggering the arrange
ment of the pole pieces so that those pole pieces
which open radially inwardly are radially further
from the central axis of the machine than those pole
pieces which open radially outwardly. Such an
arrangement increases the number of pole pieces
which can be incorporated in a stator of given radius
and prevents any increase in interpolarflux leakage
resulting from the increased number of pole pieces.
However, it will be appreciated that the dimensions
of the machine are inevitably increased as a result of such staggering and this may be unacceptable in
certain circumstances. An alternative proposal put
forward in the same patent specification is the
shortening of the radially inwardly opening pole
pieces, again allowing an increase in the number of
pole pieces, without increasing interpolar flux leak
age. However, as a result of such shortening, the
face area of the pole pieces is reduced, resulting in a
reduction in the utilization of magnetic flux.
According to the present invention, a stator of an
electromagnetic machine has an annular coil; a
plurality of U-shaped pole pieces mounted in strad
dling relationship to the coil; adjacent ones of the
pole pieces opening in opposite radial directions;
and the radially inwardly opening pole pieces each
having a radially inner portion and a radially outer
portion, the radially inner portion having a cross
section thinner than the cross-section of the radially
outer portion.
The present invention increases the number of
pole pieces that can be arranged around the stator
while maximizing the face area of the pole pieces.
Utilization of the magnetic flux is maximized and
interpolar flux leakage is maintained as low as
possible.
For a better understanding of the present invention, reference may be made to the accompanying drawings, in which:
Figure lisa diagramatical view of a prior art device;
Figure 2 is an axial end elevation showing a prior arrangement of the pole pieces; and
Figure 3 is an axial end elevation showing an arrangement of the pole pieces in accordance with an embodiment of the present invention.
Figure 1 shows, diagrammatically, the basic eiements of a typical motor suitable for use with an embodiment of the present invention. The machine has a stator 1 and a pair of rotors 2, each of the rotors 2 has a series of permanent magnets 3, 3a, arranged equidistantly around the periphery of the rotor 2 on a magnetically permeable steel annulus 4. Alternate ones of the magnets 3, 3a, have their north and south poles facing in radially opposite directions. A south pole on one rotor 2 faces a north pole on the other rotor 2 and vice-versa. The rotors 2 and the stator 1 are positioned along a common central axis 5, and the rotors 2 are fixed on a common shaft (not shown) for rotation relative to the stator 1.The stator 1 has a plurality of U-shaped pole pieces 6 opening alternately radially inwardly and outwardly from the axis 5, and equidistantly arranged around the periphery of the stator 1 at the same spacing as the permanent magnets 3, 3a. The pole pieces 6 are mounted on a stator frame, not shown to enhance the clarity of Figure 1. The pole pieces 6 provide magnetic flux paths between the magnets 3, 3a on the two rotors 2, on opposite sides of the stator 1.
The alternating arrangement of the pole pieces 6 provides a magnetic flux path alternately inwardly and outwardly of an annular coil 7 which is mounted to the frame and runs through the straddling pole pieces 6. In response to repeatedly changing the direction of current through the coil 7, the rotors 2 rotate about the axis 5 relative to the stator 1.
Referring to Figure 2, it will be appreciated that, with pole pieces 6 of equal size and shape, the minimum spacing between the pole pieces 6 is determined by the dimensions of the radially inner portion ofthe pole pieces 6. This dimension defines the maximum number of pole pieces 6 that can be arranged on a stator 1 of given radius.
Referring now to Figure 3, part of a stator arrangement showing a stator frame 10 with alternate pole pieces 6a constructed in accordance with an embodiment of the present invention is shown to the same scale as Figure 2. The pole pieces 6a opening radially inwardly toward the axis 5 have a radially inner portion 9 and a radially outer portion 8. The radially inner portion 9 has a thickness in the circumferantial direction less than that of the radially outer portion 8.
Preferably as shown, the radially outer portion 8 of each of the radially inwardly opening pole pieces 6a has a cross-sectional thickness greater than that of any portion of the pole pieces 6 opening radially outwardly from the axis 5, and the radially inner portion 9 of the radially inwardly opening pole pieces 6a has a thickness less than that of any portion of the pole pieces 6 opening radially outwardly from the axis 5. Each of the pole pieces 6, 6a are substantially equal in length and are positioned substantially the same radial distance from the central axis 5 of the stator along a plane perpendiculartothe axis 5. Slightforshortening ofthe radially inner portion 9 of the radially inwardly opening pole pieces 6a may be advantageous in some cases if it desiredfurtherto reduce leakage inductance, so long as the face area of the pole pieces 6a is not substantially reduced.
The instant invention provides a large face area for the pole pieces 6, 6a, thus achieving efficient utilization of the available magnetic flux, while continuing to maintain flux leakage at low levels. Furthermore, it is not necessary either to radially stagger adjacent pole pieces 6a orto substantially radially shorten them.
Other aspects, objects, advantages and uses of this invention can be obtained from a study of the drawings, the disclosure and the appended claims.
Claims (4)
1. A stator for an electromagnetic machine, the stator having an annular coil; a plurality of U-shaped pole pieces mounted in straddling relationship to coil; adjacent ones of the pole pieces opening in opposite radial directions; and the radially inwardly opening pole pieces each having a radially inner portion and a radially outer portion, the radially inner portion having a cross-section thinner than the cross-section of the radially outer portion.
2. A stator according to claim 1, wherein the radially outer portion of the radially inwardly opening pole pieces has a cross-section thicker than the cross-section of the radially outwardly opening pole pieces, and the radially inner portion of the radially inwardly opening pole pieces has a cross-section thinner than the cross-section of the radially outwardly opening pole pieces.
3. A stator according to claim 1 or claim 2, wherein each of the pole pieces is substantially equal in length and is positioned substantially the same radial distance from the central axis of the stator along a plane perpendicular to the axis.
4. A stator according to claim 1, substantially as described with reference to Figure 3 of the accompanying drawings.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB08410979A GB2139823B (en) | 1983-05-03 | 1984-04-30 | Stator for an electromagnetic machine |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB838311997A GB8311997D0 (en) | 1983-05-03 | 1983-05-03 | Electromagnetic machine |
GB08410979A GB2139823B (en) | 1983-05-03 | 1984-04-30 | Stator for an electromagnetic machine |
Publications (3)
Publication Number | Publication Date |
---|---|
GB8410979D0 GB8410979D0 (en) | 1984-06-06 |
GB2139823A true GB2139823A (en) | 1984-11-14 |
GB2139823B GB2139823B (en) | 1986-08-13 |
Family
ID=26286011
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB08410979A Expired GB2139823B (en) | 1983-05-03 | 1984-04-30 | Stator for an electromagnetic machine |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB2139823B (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1987002525A1 (en) * | 1985-10-12 | 1987-04-23 | Herbert Weh | Current converter-fed synchronous machine with permanent magnet excitation |
-
1984
- 1984-04-30 GB GB08410979A patent/GB2139823B/en not_active Expired
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1987002525A1 (en) * | 1985-10-12 | 1987-04-23 | Herbert Weh | Current converter-fed synchronous machine with permanent magnet excitation |
Also Published As
Publication number | Publication date |
---|---|
GB8410979D0 (en) | 1984-06-06 |
GB2139823B (en) | 1986-08-13 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19920430 |