Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1989-08-11
1991-09-24
Beha, Jr., William H.
Electrical generator or motor structure
Dynamoelectric
Rotary
310162, 310257, H02K 2112, H02K 4103, H02K 2900
Patent
active
050516418
DESCRIPTION:
BRIEF SUMMARY
In known alternating current motors of the type mentioned (EP-A-201 021) the no-load field is generated over permanent magnets embedded in the rotating exciter part, the flux-conducting pole surfaces of which face the air gap plane. With this construction of the exciter system the forces rise with increasing magnet thickness. The force increase finds its limit when the magnet height comes into the vicinity of the pole division. Then the effectiveness of the armature field declines, since this no longer extends into the inner zone of the permanent magnets. The armature field then goes more and more over into a stray field running in longitudinal direction. This field behavior is to be seen in connection with the fact that on each armature side there are arranged pole elements with alternating polarity. Corresponding to potential differences thus present there are formed stray fluxes which are superposed on the force-forming field components. They load the magnetic circuit, increase the inductance and thereby contribute to the retardation of the commutation.
Because of the limitation of the magnet height the possibilities of reducing the pole division are further limited. A reduction of the pole division leads in the known alternating current motors to a reduction of the magnet height and therewith necessarily to a flux reduction. A small pole division, however, is desired in machines (motors) with transverse flux conduction, since it makes possible lower winding losses by reason of the smaller effective winding length.
It is further a known practice (EP-A126 997) to use permanent magnets not only in the form of direct allocation to the useful gap (flat arrangement) in which the flux density in the useful gap is about equal to that of the permanent magnets, but also in collector configuration in which the permanent magnets lie substantially perpendicular to the useful gap. The permanent magnets lie here between soft iron poles, and the cross section area of the permanent magnets is greater than the surface of the pole facing the useful gap. Hereby the flux density in the magnet can be kept less than in the useful gap. The disadvantages of the known collector arrangement lie in high armature feedback (Ruckwirkung) and great stray flux. These disadvantages are excluded according to the teaching of EP-A-126 997 by the means that the soft iron poles of the rotor present two adjacent partial poles, between which there is provided a magnetically nonconducting separating gap that is greater than the useful gap, and that the partial poles are constructed to converge proceeding from the useful gap. The partial poles there are expediently divided transversely to the direction of movement into a plurality of pole lamellae which are separated by nonmagnetic interspaces and which reduce the strong armature feedback arising with undivided poles. Further, the construction of the partial poles with pole lamellae as well as magnet height as great as possible is supposed to counteract a field distortion in the useful gap.
The problem of the invention is to construct alternating current machines of the type according to the category in such a way that such motors are feasible both with higher efficiencies and also with higher performance densities.
This problem is solved according to the invention by the features set forth hereinafter.
The construction of the exciter part according to the invention offers also advantages for the layout of the stator. The smaller magnetically active air gap, as compared with the flat arrangement, allows for equal force densities a smaller armature flooding. It is also possible, however, with equal armature flooding to achieve a higher force density (force per volume unit and force per mass unit).
Expedient formations of the invention are object of the dependent claims.
The invention is illustrated in the drawing in examples of execution and is described in detail in the following with the aid of the drawing. In particular:
FIG. 1 shows schematically the structure of the alternating current moto
REFERENCES:
patent: 3411059 (1968-11-01), Kaiwa et al.
Beha Jr. William H.
J. M. Voith GmbH
Jones Judson H.
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