Electrical Machine

The invention concerns an electrical machine, specifically a rectifier-energized synchronous machine on the transversal flow principle. A machine designed according to this operating principle is known from DE-PS 37 05 089.

The so-called transversal flow concept is based on exciting the stator field not in the longitudinal direction of the machine--i.e., parallel to the axis of rotation of the rotor--but in peripheral direction, that is, along the direction of movement as the rotor rotates. To that end, the rotor has at least a pole structure of two side-by-side rows of permanent magnets alternately magnetized in peripheral direction and soft iron elements, the two rows being separated by an intermediate layer of magnetically and electrically nonconductive material. In principle, this pole structure is of drum shape.

The stator consists essentially of two parts, namely an outer stator arranged radially outside the pole structure and an inside stator arranged radially within the pole structure. Each stator part features soft iron armature elements which essentially are fashioned U-shaped and whose open shanks are opposed in magnets of the rotors, from radially inside or radially outside, across an air gap. The prior machine features for excitation, for each stator part, an annular winding extending in peripheral direction.

With this arrangement characterized by a simple winding structure and with a direction of magnetic flux extending transverse to the direction of movement, high power densities can be achieved, especially when selecting small pole pitches. The electrical lead to the two annular windings of the stator halves must be passed through the armature elements. For removal of the heat accuring in the windings there are as well only the spaces between the armature elements available. On the inside stator, however, the spaces between the armature elements are at identical pole number and smaller radius considerably smaller than on the outside stator. Thus, the space conditions are especially unfavorable for the inside stator, entailing problems in the feed line design, winding structure and assembly of the inside stator.

The problem underlying the invention consists in improving the winding structure and the excitation of an electrical machine of the initially named category to the effect that the line routing, heat removal and assembly will be facilitated.

This problem is solved in that the excitation of the stator is concentrated in a sole annular winding extending in peripheral direction and in that this sole annular winding is accommodated only in one of the two stator halves. The other stator half thus remains void of an annular winding and, thus, magnetically inactive. This stator half forms thus a magnetic back circuit between the two permanent magnet rows on the pole structure of the rotor. This measure entails a significant simplification of the winding structure on the motor and a considerably simplified assembly, in conjunction with elevated operational safety, specifically as regards the insulation resistance in view of the heat load to be expected.

In one embodiment of the invention, the sole annular winding is disposed in the outside stator, allowing the inside stator to remain void of a winding. The armature elements of the no-winding stator part may be fashioned as laminated back circuit elements, specifically as C-cores, and arranged in the peripheral direction at a spacing corresponding to twice the pole pitch on the pole structure of the rotor. The armature elements of the stator part accommodating the annular winding may be fashioned as well as C-cores which embrace the annular winding in U-shaped fashion on three sides. The rotor may feature two pole structures which are arranged symmetrically on both sides of the central plate, with the two pertaining stators having a structure such that the sole annular windings are always arranged in the same stator part, i.e., on the inside stator or preferably on the outside stator. This measure assures a quiet non-vibrating running of the motor.

An embodiment of the invention will be described hereafter with the aid of the drawing, which shows in

FIG. 1, a schematic longitudinal section through the electrical machine;

FIG. 2, a schematic view of the rotor pole structure and of the stator elements embracing them.

The machine illustrated schematically in section in FIG. 1 comprises a stator housing 1 in which a rotor 2 with its shaft 3 is rotatably mounted. The rotor consists of a central disk 4 on the radially outer area of which there are two pole structures 12 arranged, symmetrically toward both sides and coaxially to the axis of rotation of the shaft 3. These pole structures are comprised of permanent magnets 13 which in two rows, in peripheral direction and side by side, are alternately polarized and adjacent to soft iron elements 14, with all parts being separated from each other by electrically and magnetically nonconductive insulating layer 15 (FIG. 2), which is, preferably comprised of plastic. Embedded in plastic, the disk 4 forms with the pole structure 12, the magnets 13 and soft iron elements 14 (illustrated in FIG. 2) a rotary body reinforced in itself. Separated by an air gap 11, each of the pole structures 12 is opposed by a stator assembly 5 consisting of a radially outer outside stator 6 and a radially inner inside stator 7. Each outside stator 6 is comprised of a plurality of U-shaped armature elements 9 whose open shanks oppose the permanent magnet 13 of the pole structure 12 of the rotor. Contained within each outside stator 6 of each respective stator assembly 5 surrounded on three sides by each respective armature element 9 is an armature or annular winding 8 extending in peripheral direction. The inside stator 7 is void of an annular winding and merely forms the magnetic back circuit for stator excitation between the permanent magnets 13 on the radially inner side, namely in a radial plane (transversal flow principle).

Armature winding 8 is disposed only in one of the outside stator 6 and inside stator 7, the other of the outside stator 6 and inside stator 7 being void of armature winding 8.

FIG. 2 shows schematically and in extended position a section of one pole structure 12 of the rotor and the surrounding stator parts 6, 7. Visible are the two rows of permanent magnets 13 and soft iron elements 14 which are arranged one behind the other and combined by a magnetically and electrically nonconductive insulating layer 15 in peripheral direction (FIG. 2). The permanent magnets 13 of the one row, as compared to those of the other row, are poled in different direction, creating a magnetic flux direction according to arrow P. The two rows of permanent magnets 13 with soft iron elements 14 are separated from each other also crosswise to their peripheral direction by magnetically and electrically nonconductive insulating layer 15 (FIG. 1), preferably plastic, but nonetheless connected with one another in load-bearing fashion.

Also evident is that the outside stator 6 features soft iron armature elements 9 which in peripheral direction are arranged spaced from one another a distance 2T. The armature elements 9 are fashioned as C-cores 10, i.e., are laminated. The same is true for the armature elements of the inside stator 7, which are arranged radially inside the pole structure 12, as illustrated in FIG. 1. The armature elements 9 of the out-side stator are peripherally offset by the pole pitch T relative to the armature elements of the inside stator. The pole pitch T is given by the thickness of the permanent magnets 13 and of the soft iron elements 14 including each respective magnetically and electrically nonconductive insulating layer 15. Also the armature elements of the inside stator 7 are peripherally spaced by twice the pole pitch T, which with the smaller radius of the armature elements on the inside stator corresponds to a smaller absolute value of the spaces. Therefore, the annular winding 8 is favorably arranged on the outside stator 6, with the electrical lead 16 to this annular winding preferably being routed between the armature elements 9 in the radially outer area. In this way it is possible to design the machine with smaller values for the pole pitch T and, thereby, generate high power densities. Nonetheless, this measure avoids assembly difficulties, a complex winding structure for the inside stator and high thermal load.