Three-phase dry-type transformer, type DTG 40/20

©  Technisches Museum Wien, Photo: Peter Sedlaczek
Collection Area
Energy & Mining
Electrical Engineering
1970 - 1979
At the moment this object is not published in the museum.

Transformers are used to adjust electrical voltage levels. This is so that electrical appliances can be operated properly, but also to be able to generate high voltages.

A transformer is a comparatively simple device without any moving parts. In its simplest form it consists of two coils wound around an iron core; each coil must have a different number of windings. The ratio of winding turns corresponds to the ratio of voltages.

Transformers are used wherever the available voltage is too high or too low for the operation or transmission; they are therefore fitted inside virtually all electrical devices that we use on a daily basis: mobile phones, model railways and mixers usually require a lower voltage than the 230 V from the mains socket.

For electrical energy to be transmitted over long distances, the voltage has to be stepped up to allow smaller cross-sections. The electrical voltage is stepped down again once it reaches the (geographic) vicinity of the end user.

If the electrical energy produced by a generator were transmitted directly to the consumer without being transformed, the power lines would require very high cross-sections indeed. Power cables or power rails as thick as that would be much too expensive and impractical from the point of view of technical feasibility.

It was the development of transformers in the 1880s that made comprehensive electrification possible. The basic principle of the transformer has not changed in the course of history; only its design has been optimised mainly as a result of better materials. It meant that ever smaller and lighter types could be built, with lower-loss versions.

The three-phase dry-type transformer exhibited here from 1970 transforms 20,000 V (i.e. medium voltage) into 525 V and was used by Messrs. Bunzl & Biach in the paper manufacturing industry. Usually the coils on a transformer are immersed in oil for cooling purposes and electrically insulated; by contrast dry-type transformers do not use transformer oil. Here the high voltage windings are cast in resin, which means the device requires less maintenance; a mobile version is achieved by equipping it with a carriage.

Donated exhibit; our warmest thanks to: BARTH GmbH E-Motoren & Trafos

Inv.Nr. 77554

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