Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-10-12
2001-01-16
LaBalle, Clayton (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S049540
Reexamination Certificate
active
06175177
ABSTRACT:
The invention relates to a permanent magnet-excited assembly of an electrical machine, and to a process for the manufacture of such an assembly; in particular of a synchronous machine with a ferromagnetic body and permanent magnets arranged therein, preferably for application as compact solutions for drives.
Rotating electrical machines operating with permanent magnet excitation are known as transversal flux machines, on the one hand. Such machines structured on the basis of the transversal flux principle can be operated both as motors and generators. As a rule, the rotor consists of one or a plurality of concentric rings, which are separated from each other by one or a plurality of plastic rings axially lined up in a row and disposed between said concentric rings, or by rings consisting of another type of electrically nonconductive material, and/or by a rotor disk, with so-called collector or soft-iron elements being alternatingly arranged in such rings along the circumference. Such collector or soft-iron elements are normally structured from axially laminated electrosheet material, with magnets being arranged on the latter. Such concentric rings are referred to also as the pole structure. The problem posed in connection with all transversal flux machines is the mechanical strength of the rotor structure. It is known that attempts are being made to obtain the required strength by gluing, whereby the glued joints are additionally reinforced with simple construction elements such as, for example bolts, screws, rivets etc. Also, bandages are increasingly employed on the surface of the rotor in order to manage the stress caused by centrifugal forces. One drawback of such additional elements is that the latter substantially increase the volume of the rotor, and that the manufacturing and processing expenditure is high. Furthermore, if the safety elements are arranged through the rings, either the magnets in the divided form are subjected to high working and manufacturing expenditure, or the soft-iron elements if such additional elements are passed through or arranged within the region of said soft-iron elements. Moreover, with such designs, the enlargement of the rotor in the radial direction causes deterioration of the surface-to-volume ratio, which determines the cooling conditions, whereby cooling is is problematic in connection with transversal flux machines in any case. DE-PS 195 35 256 describes a solution which is expected to avoid said drawbacks. For said solution, provision is made for a mulitude of additional pulling elements acting in the axial direction, such elements being disposed on at least one diameter outside of the zone enclosed by the so-called limit diameter. However, this solution further increases the manufacturing expenditure as compared to the glued design.
Electrical machines with permanent-magnet excitation have been developed in the course of the past years with increasingly higher capacities, favored by engineering measures, special control circuits with higher switching frequencies, and permanent magnet materials of high energy density which became available in the meantime. Capacities have been achieved in the meantime on such high levels that the problem of eddy current losses is being noticed in substantially negative ways. It is generally known in the field of electric machine engineering to structure both the stator and the rotor in a laminated way in order to avoid eddy current losses. Laid-open DE-OS 196 48 758 describes an electrical machine with permanent-magnet excitation with ferromagnetic rotor feedback, where laminated sheet disks and a type of layered permanent magnet are employed for avoiding eddy current losses. Both with the external rotor and the internal rotor machine, the permanent magnets are arranged here externally on the circumference of the lamination. The drawback here is that the manufacturing expenditure continues to be high for heavy-duty machines.
In DE-OS 44 23 620, individual permanent magnets are arranged in a cylindrical yoke consisting of isotropic permanent magnet material. This design, however, is suitable only for rotating electrical machines with very low capacity. The rotor is designed in this connection in the form of a bell rotor.
Several permanent magnets in a cylindrical rotor body are known from DE-OS 40 33 454. However, here, the permanent magnet material is injected for reasons of mechanical strength. This solution limits the application of modern permanent magnet materials with high energy density and is suitable only for rotating electrical machines with low output. The exclusive use of ferromagnetic material for the basic body of the rotor increases the leakage field component of the permanent magnet, which conditions the use of an increased amount of permanent magnet material.
The invention is based on the problem of providing a permanent magnet-excited assembly of an electrical machine that improves the mechanical strength of said assembly overall and also of the components of said assembly; which reduces the number of components of the assembly; and enhances the efficiency of the overall heavy-duty electrical machine; as well as on the problem of developing a process for the manufacture of said assembly that reduces the production expenditures and permits its production in series.
According to the invention, the problem is solved by the characterizing features of the first two claims. The permanent magnet-excited assembly as defined by the invention, and the process for its manufacture lead to the realization of a construction coming close to the tested principles in other fields of electric machine engineering. In particular, the mechanical strength of the entire construction is suitable for rough operating conditions. The operational safety and the useful life of the drives produced with the permanent magnet-excited assemblies as defined by the invention can now satisfy the requirements for such application cases. And series production is feasible with known machines, plants and technologies employed in electrical machine building.
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patent: 4445062 (1984-04-01), Glaser
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patent: 6029336 (2000-02-01), Kliman et al.
patent: 40 33 454 (1992-04-01), None
patent: 689 06 910 (1993-11-01), None
patent: 44 23 620 (1996-01-01), None
patent: 195 35 256 (1997-04-01), None
patent: 196 48 758 (1998-06-01), None
Kuss Hans
Sabinski Joachim
Collard & Roe P.C.
LaBalle Clayton
VEM Sachsenwerk GmbH
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