GB2161329A - Insulation film for the production of safety clearance in transformer windings - Google Patents

Abstract

An insulation film for disposition between the layers of a winding of a transformer on a spool has corrugated edges which prevent the wire winding from slipping and also ensure the safety leakage paths between the windings, so that transformers constructed in this way no longer have to be impregnated or cast. <IMAGE>

Description

SPECIFICATION Insulation film for the production of safety clearances in transformer windings Transformer windings, in particular with low Ca- pacity, are usually designed according to the prior art so that suitable plastic films are either wound precisely between the spool flange as intermediate layers between the wire layers or are feathered at the edges, the width being greater than the clearance between the flanges. Both methods have disadvantages. In the case of the film which is cut flat, although the winding can be guided up to the flange, there is, however, the risk of the winding wire slipping through between the flange and film onto the winding arranged therebelow.

In the case of the feathered intermediate layer, individual sections can be underwound or become detached, so that the layer insulation is not guaranteed to be safe in this case either.

The electrical safety requirements however stipulates that leakage paths (e.g. 4 - 8mm) be maintained between potential carrying windings in addition to layer insulation.

This can be ensured according to the invention by using an insulation film corrugated in the manner of a rack formed on the edges by plastic shaping. As a result of the corrugation, the layer winding only rests on the flat part of the film treated in this way, the winding ends can easily be guided out in the interspaces which remain free between the corrugation, without the leakage path being altered.

A further advantage of this intermediate layer insulation according to the invention is that fact that the transformer windings thus constructed no longer have to be (vacuum-) impregnated and can therefore be produced far more economically.

An insulation film according to the invention is illustrated in perspective in the drawing, in which: Figure 1 is the part of the film which remains flat; Figures 2 and 3 are the edges of the film according to the invention corrugated in the manner of a rack, the width of the film being able to be set in accordance with safety requirements.

It will be seen from the drawing that the insulation film has a central portion 1 which is flat and two opposite edge portions 2 and 3 which are of uniform thickness but which are shaped into sinusoidal curves. The change from the central portion to the edge portions 2 and 3 is abrupt, and the thickness of the film is uniform at all points.

In use, the film is laid onto a layer of transformer windings, and a further layer of winding is laid on the central portion 1. The abrupt changes between the central portion 1 and the edge portions 2 and 3 serve as barriers to keep the upper layer of transformer winding from slipping over the edge of the film to contact the layer of winding below.

The layer of transformer winding can be slid along the film, since it does not contact the corrugations of the edge portions.

The corrugations need not be in the form of sinusoidal curves.

1. An insulation film for transformers comprising a central flat portion, and two opposite edge portions which are corrugated.

2. A film as claimed in Claim 1 wherein the central portion and the edge portions are of uniform thickness.

3. A film as claimed in Claim 1 or 2 wherein the corrugations are sinusodial.

4. An insulation film for transformers substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

5. A transformer comprising a plurality of winding layers, and an insulation film as claimed in any one of Claims 1 to 4 between adjacent layers.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Insulation film for the production of safety clearances in transformer windings Transformer windings, in particular with low Ca- pacity, are usually designed according to the prior art so that suitable plastic films are either wound precisely between the spool flange as intermediate layers between the wire layers or are feathered at the edges, the width being greater than the clearance between the flanges. Both methods have disadvantages. In the case of the film which is cut flat, although the winding can be guided up to the flange, there is, however, the risk of the winding wire slipping through between the flange and film onto the winding arranged therebelow. In the case of the feathered intermediate layer, individual sections can be underwound or become detached, so that the layer insulation is not guaranteed to be safe in this case either. The electrical safety requirements however stipulates that leakage paths (e.g. 4 - 8mm) be maintained between potential carrying windings in addition to layer insulation. This can be ensured according to the invention by using an insulation film corrugated in the manner of a rack formed on the edges by plastic shaping. As a result of the corrugation, the layer winding only rests on the flat part of the film treated in this way, the winding ends can easily be guided out in the interspaces which remain free between the corrugation, without the leakage path being altered. A further advantage of this intermediate layer insulation according to the invention is that fact that the transformer windings thus constructed no longer have to be (vacuum-) impregnated and can therefore be produced far more economically. An insulation film according to the invention is illustrated in perspective in the drawing, in which: Figure 1 is the part of the film which remains flat; Figures 2 and 3 are the edges of the film according to the invention corrugated in the manner of a rack, the width of the film being able to be set in accordance with safety requirements. It will be seen from the drawing that the insulation film has a central portion 1 which is flat and two opposite edge portions 2 and 3 which are of uniform thickness but which are shaped into sinusoidal curves. The change from the central portion to the edge portions 2 and 3 is abrupt, and the thickness of the film is uniform at all points. In use, the film is laid onto a layer of transformer windings, and a further layer of winding is laid on the central portion 1. The abrupt changes between the central portion 1 and the edge portions 2 and 3 serve as barriers to keep the upper layer of transformer winding from slipping over the edge of the film to contact the layer of winding below. The layer of transformer winding can be slid along the film, since it does not contact the corrugations of the edge portions. The corrugations need not be in the form of sinusoidal curves. CLAIMS

1. An insulation film for transformers comprising a central flat portion, and two opposite edge portions which are corrugated.

2. A film as claimed in Claim 1 wherein the central portion and the edge portions are of uniform thickness.

3. A film as claimed in Claim 1 or 2 wherein the corrugations are sinusodial.

4. An insulation film for transformers substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

5. A transformer comprising a plurality of winding layers, and an insulation film as claimed in any one of Claims 1 to 4 between adjacent layers.