Stator Winding of a Rotating Electrical Machine and a Method for the Production of Such a Stator Winding

Abstract

A stator winding (10) of a rotating electrical machine, in particular at operating voltages of above 6 kV, is provided with preformed coils or bar windings, wherein the individual conductors of the preformed coils or bar windings are inserted into slots in the region of the stator body and are connected to one another in an end winding region outside of the stator body, and wherein the conductors (14) are surrounded by a main insulation (15) and a corona-discharge protection (16) covering said main insulation (15). For such a stator winding, operation of the machine or generator at higher temperatures or higher altitudes than originally planned is made possible without changing the geometry of the end winding by providing additional structure (17) for improving the resistance to corona discharge of the conductors (14) in the end winding region.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail below with reference to exemplary embodiments in connection with the drawing, in which:

FIG. 1 shows a schematic illustration of the connection of two Roebel bars with a small bend (FIG. 1a) and a severe bend (FIG. 1b) of the bars; subfigure 1c clarifies the relationship derived in the text between the distance between two parallel bars in the slot section and in the end winding region of the bars;

FIG. 2 shows a detail from the winding scheme of a 3-phase generator with 2 parallel circuits (the slot section is illustrated as being severely shortened); the electrical outgoing lines, phases U, V, W, are located in the end winding space (13′) illustrated at the bottom; the last passage of the bars in phase W2 (V2) is illustrated by a bold continuous (dashed) line; approximately the full phase-to-phase voltage (U_n) is present in the region (13′) between phases W2 and V2;

FIG. 3 shows, in a detail of one side, the construction of the insulation, the corona-discharge protection, and the top layer of the Roebel bars in the end winding region in accordance with a preferred exemplary embodiment of the invention; and

FIG. 4 shows a scanning electron microscope image of the main insulation of a Roebel bar shown in FIG. 3, having a plurality of layers of glass mica tapes (mica layer 18, glass layer 19, epoxy resin 20).

Claims

1. A stator winding of a rotating electrical machine, which stator winding comprises: a stator body including slots;preformed coils or bar windings having individual conductors inserted into stator body slots and connected to one another in an end winding region outside of the stator body;a main insulation surrounding the conductors and a corona-discharge protection covering said main insulation; andmeans for improving the resistance to corona discharge of the conductors in the end winding region.

2. The stator winding as claimed in claim 1, wherein the means for improving the resistance to corona discharge comprises an additional top layer applied on the outside to the corona-discharge protection.

3. The stator winding as claimed in claim 2, wherein the top layer comprises a mica tape impregnated with an epoxy resin and having a glass or plastic substrate, and wherein the mica tape is wound around the conductor in a semi-overlapping manner.

4. The stator winding as claimed in claim 3, wherein the mica tape of the top layer comprises a glass filament fabric, and further comprising thin mica sheets applied in a large number of layers onto said glass filament fabric, the thin mica sheets being oriented parallel to the plane of the tape.

5. The stator winding as claimed in claim 4, wherein the quantitative proportion of mica in the impregnated mica tape is greater than half.

6. A method for the production of a stator winding as claimed in claim 1, the method comprising: applying the means for improving the resistance to corona discharge or the top layer as early as when the main insulation and the corona-discharge protection are wound onto the conductor; andpermanently connecting all the layers jointly to the conductor.

7. The method as claimed in claim 6, wherein the means for improving the resistance to corona discharge or the top layer comprises a mica tape having a glass or plastic substrate, and wherein permanently connecting all the layers comprises permanently connecting the applied mica tape, the main insulation, and the corona-discharge protection to the underlayer by being impregnated with a synthetic resin, and subsequently curing the resin.

8. A method for the production of a stator winding as claimed in claim 1, the method comprising: first, providing the conductor permanently with the main insulation and the corona-discharge protection; andthereafter applying the means for improving the resistance to corona discharge or the top layer and permanently connecting said means to the conductor.

9. The method as claimed in claim 8, wherein the means for improving the resistance to corona discharge or the top layer comprises a mica tape having a glass or plastic substrate, and further comprising: winding the mica tape, after the corona-discharge protection has been impregnated and cured, over the corona-discharge protection, and then adhesively bonding the mica tape to the corona-discharge protection.

10. A stator winding as claimed in claim 1, wherein the rotating electrical machine is configured and arranged to operate at voltages above 6 kV.

11. The stator winding as claimed in claim 4, wherein the quantitative proportion of mica in the impregnated mica tape is greater than 70%.

12. The method as claimed in claim 7, wherein the synthetic resin comprises an epoxy resin.