Medium frequency transformer

Medium-frequency transformers are transformers that are designed in the field of electrical power engineering and drive technology for frequencies in the range from a few 100  Hz to a few 1 kHz ( medium frequency ). These transformers differ from normal mains transformers, which are operated with the mains frequency of 50 Hz that is common in Europe , in that they have a smaller iron core , because as the frequency of the electric current increases, the iron cross-section can be made smaller while the power transmission remains the same.

The use of medium frequency allows for specially adapted transformers to reduce device weights. Due to the increasing spread of different forms of switched-mode power supplies , medium-frequency transformers have lost importance.

Application examples

Examples of the use of medium frequencies and special transformers are:

• In airplanes, the various voltages required in the previously common tube devices for radar , on-board radio, etc. could be generated in a weight-saving manner at an on-board network frequency of 400 Hz using medium-frequency transformers. Gyroscopic devices and small drives also benefited from 400 Hz.
• Electric railroad multiple units (high-voltage side inverter + MF transformer).
• Medium-frequency transformers are often built into welding power sources for spot welding guns in order to avoid thick power supplies (several thousand amperes are required) and to keep the guns light and mobile (e.g. on robot arms in automobile production).

At frequencies up to a few kHz, transformers can still be manufactured with laminated electrical steel cores, but the sheet thickness must be less (0.05 ... 0.1 mm) to avoid higher eddy current losses . B. 0.35 ... 0.5 mm.

Transformers for audio frequencies and output transformer of tube amplifiers are not called medium frequency transformers although here apply the same physical laws.

literature

• Andreas Steimel: Electric traction vehicles and their energy supply . Oldenbourg Industrieverlag, 2006, ISBN 978-3-8356-3090-1 .

Individual evidence

1. ↑ Smaller, lighter, more efficient - the power electronic traction transformer (PETT) (PDF) - press article - Asea Brown Boveri (ABB) - accessed on April 4, 2015
2. ^ Gerhard Babiel: Electrical drives in vehicle technology . Springer, 2009, ISBN 978-3-8348-9590-5 , pp. 73 .

Web links

Wiktionary: medium frequency transformer  - explanations of meanings, word origins, synonyms, translations