DE1958028A1 - Resin-impregnated transformer coil - Google Patents

Abstract

Transformer or throttle coil is impregnated with casting resin by immersing the winding in a resin bath, and passing a current through the coil to heat the conductor for hardening the resin. When a sufficient resin layer thickness is reached, the winding is removed from the bath, and the resin is hardened in a heated chamber. Uniform layer thickness is pref. obtained by differential heating or cooling of the resin bath, container at various positions. Pref. a resin mixture is used whose viscosity as a function of temp. and time rises gradually at first and then very rapidly. Casting moulds are not required and the hardened resin does not have shrink holes.

Description

Coil for cast resin transformers, chokes, W transducers and dergi.

There are coils for transformers, chokes, transducers and the like Devices already known that are impregnated with thin, hot-curing resin are and a more or less thick-walled envelope, which is also made of a cast resin molding material exists, have. Such coils have very good high voltage properties, because the impregnating resin, when used appropriately, clears the gaps without pickling the cavity between the winding wires, so that no turn and winding breakdowns can occur through partial discharges. In addition, the winding is through the GieSharz coating protected from moisture. The entire cast share coil is a self-supporting rigid one Structure that is particularly useful when reinforced with glass fiber fabric cast in is able to safely absorb the dynamic forces that occur during short-circuiting.

The disadvantage is that the production of the cast resin coils in general requires complex casting molds, especially for small numbers of items The coils to be produced greatly increase the cost of building the finished device.

Relatively small numbers often occur with transformers and chokes on, as this is for each rated power, rated current and rated voltage usually a separate set of molds is required.

With the long-known type of conventional production of dry transformers and similar devices there is no need for casting molds, that the windings are immersed in a bath filled with impregnating resin. To After soaking, the windings are removed again, the liquid resin drips off and the resin adhering to the winding bond then hardens.

The manufacturing costs for such dry-insulated devices are of course much lower than when building transformers fully encapsulated with cast resin. Chokes, Neßwandlern and the like.

A coil made in this way is, however, only extremely thin because of the Resin layer only partially protected against the ingress of humidity. By the lack of a resin jacket, the short-circuit strength of such coils is reduced. In the case of devices for operating voltages above approx. 1000 to 10000 V, the service life be affected because the spaces between the winding wires are air-filled Contain cavities in which partial discharges can occur.

In the production method according to the invention, on the one hand, there are none Casting molds required and, on the other hand, can be void-free with suitable application Impregnation of the windings and a sufficiently thick top layer on the surface of the coils can be achieved.

The coils are made from the conductor material, for example insulated copper wire in cylinder shape, wrapped and tied with fiberglass fabric or a other filler covered inside, outside and between the layers. As a bobbin When winding, a cylinder that can be dismantled is expedient. Wood or another suitable material used, according to removed again after winding will. The self-supporting coil made of Eupfer wire and fiberglass fabric is then after placed in a vessel using a conventional drying process under the action of vacuum and heat, which is filled with low-viscosity casting resin.

The invention consists in the fact that an electrical through the winding Electricity is conducted. This heats up the conductor material and the casting resin in the immediate vicinity begins to harden. Direct current is cheaper than alternating current, since the driving voltage can then be lower. The voltage must namely be less than about 500 to 1000 V in order to discharge glow discharges under vacuum to avoid.

The hardening of the resin begins at the warmest point, i.e. immediately on the conductor surface. The casting resin thus shrinks onto the conductor without voids on. The hardened or gelled layer thickness increases over time. For better impregnation, overpressure can also be applied after the vacuum, as is known can be applied.

When the layer is thick enough, the electricity is switched off, the rest of the time Any casting resin that is still liquid is quickly drained from the vessel or the coil is removed. If this method is used appropriately, the remaining resin can still be used for others Coils are used.

The fiberglass fabric on the spools holds that like in a network gelled gelatinous casting resin firmly in itself. By wiping off the surface be smoothed if necessary. The coil is then placed in a heating chamber finally hardened.

The temperature at the slider of the current-carrying coil is normally not the same size everywhere. If the coil is placed vertically, it is the highest Temperature near the top. This will create the gelled layer in this Area may be a little stronger than in the other places. To do this avoid, the casting vessel is cooled or if necessary in the upper area In the hall, external heat supply in the upper part of the Deil is less heated. Also can it may be advisable to keep stirring the resin to mix it thoroughly.

In order to optimize the described procedure are for the respective Coil type first of all practical experiments are required to determine the appropriate production process and to find out a temperature distribution in the coil that is as uniform as possible.

What is important here is the optimal value of the current strength and their duration. In addition, the composition of the casting resin mixture must be optimized will.

Mixtures in which the viscosity occurs during curing are favorable depending on the temperature and the time after initially as flat as possible Very quickly shows the steepest possible increase.

The inventive idea can sort and with different types of resin can be used with any coil structure. It is thus possible to manufacture of cast-resin-encapsulated transformers, chokes, transducers and the like cheaper.

Claims (3)

Patent claims fx coil for cast resin transformers, chokes, measuring transformers and The like, characterized in that the winding during the manufacture of the coil is immersed in a resin-filled bath and at the same time an electric one through the winding Current is passed, whereby the conductor material heats up and the resin in the immediate environment begins to harden, further characterized in that If the layer is thick enough, the winding is separated from the bath again and in the final hardening of the cast resin coil takes place in a heating chamber. 2. Coil for cast resin transformers, chokes, measuring transformers and The like according to claim 1, characterized in that in order to achieve a uniform Layer thickness of the vessel of the resin bath in different places to different degrees is cooled or heated. 3. Coil for cast resin transformers, chokes, heat converters and The like, according to claims 1 and 2, characterized in that a resin mixture is used in which the viscosity depends on during curing temperature and time very quickly after initially as flat a course as possible shows the greatest possible increase.