Insulated Dynamo Windings

The present invention relates to a direct-current dynamo electric machine, and more particularly to a dc motor suitable as a drive motor for electric road vehicles, such as trolley cares, trolley buses, and the like, and especially to such motors having commutating poles, as well as to the manufacture of making the commutating pole windings.

dc machines, particularly for vehicular use, are described in the book "Electric Machinery" by Dr. Germar Muller, VEB-Verlag (Publishers) Berlin, p. 295, see also FIG. 16.16 thereof. Other publications describe such motors.

It is an object to provide a method and a structure for the commutating poles of dc motors suitable for automotive use, particularly street vehicles, and the like, which permits spark-free commutation while requiring but little space.

Briefly, the commutating poles are wound with a strip of conductive material, typically copper, which is essentially rectangular in cross section, the winding being wound on edge, that is, with the narrower side forming the curved portion, and the wider side of the cross-sectional area being planar and located in spiral planes around the axis of the pole. The respective layers or winding turns are insulated from each other by hardened, typically sintered powder applied in a fluidized-bed apparatus.

FIG. 1 is an end view of a vehicular-type electric motor having four commutating poles;

FIG. 2 is a top view of a commutating pole coil;

FIG. 3 is a side view, the illustrations of FIGS. 2 and 3 being to an enlarged scale; and FIG. 4 is a block diagram of the steps of making the windings.

The vehicular-type dc motor has a soft iron armature 1 with four pole shoes 2, each one carrying an exciter winding 3. Four commutating poles 4 are located between the respective main poles 2. Each one of the commutating poles or cores carries a commutating pole winding 5. The commutating pole windings 5 are made of a copper strip 6 which, in cross section, is rectangular. The copper strip 6 is wound on edge, that is, the narrower side of the rectangle forms the curves at the end of the winding, the wider sides of the rectangle forming the top and bottom surfaces of the loops of the windings-see FIGS. 2 and 3. In this specification and claims, this type of winding is referred to as on "edge". The commutating pole windings 5 are so wound that respective winding loops or spirals are slightly spaced from each other. They can be wound tightly but, after having been wound, they will form slightly spaced spirals due to the springiness or resilience of the material, so that the windings will have the configuration, when looked at from the side, as seen in FIG. 3. Initially, the windings are wound with blank or uninsulated copper strip. The respective turns of the windings are insulated from each other by exposing the windings to a fluidized-bed process in which a thin insulating layer 7 of polyethylene, approximately 0.3 mm to 0.4 mm thick, is applied. Any other polymerizable powder which can melt easily can be applied, the powder precipitating on the blank or uninsulated copper of the conductor. After precipitation of the powder on the conductor, it is cured or hardened to a uniform insulating layer 7 on the individual spirals of coalesced powder.

During the fluidized sintering process, the ends 8 of the copper strip are preferably coated with a covering which prevents precipitation of the sinter powder, the covering later on being stripped off. Thus, the end portions of the windings are left uncoated to provide for ease of electrical connection thereto.

Rather than using polyethylene, polyurethane may also be used. The strip-off coating over the ends 8 of the conductor can be removed before or after the sintering process.