Bell transformer

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Old bell transformer

A bell transformer is a transformer that is intended for the operation of door signal systems ( bell , buzzer or gong ). According to valid standards, e.g. B. in Germany the DIN VDE 0551, bell transformers must be safety transformers and "absolutely short-circuit proof".

construction

Bell transformer for top hat rail mounting
Bell transformer installed in sub-distribution

In the case of bell transformers, the air gap is selected so that the current flowing in the event of a short circuit in the secondary winding does not lead to any inadmissible heating of the transformer. Because of this design, bell transformers have a relatively high short-circuit voltage , which is 40 percent. According to DIN VDE 0550, the primary winding may only be designed for one voltage , which means that it consists of a continuous coil without a center tap. Bell transformers are designed so that the output terminals (secondary voltage) are freely accessible. In order to get to the terminals of the secondary coil, the terminals of the mains voltage do not have to be exposed. Both the coil for the mains voltage and the coil for the low voltage are provided with reinforced insulation in accordance with DIN regulations . The secondary winding usually has several taps with the voltages 3  volts , 5 volts, 8 volts and 12 volts. Standard bell transformers have secondary voltages of 3 volts, 5 volts and 8 volts, in special cases transformers with secondary voltages of up to a maximum of 24 volts are used. The no-load voltage in bell transformers can be up to 2.5 times the nominal voltage.

Services

Bell transformers are built for rated currents of the secondary winding up to 2 amps. Depending on the type, the nominal power is between 8 and 48  VA . Due to their design, bell transformers have high idle losses , depending on the size of the transformer, between 4 and 10 VA. These high no-load losses mean that between 40 and 100 kilowatt hours are consumed each year , with the power loss alone accounting for between 35 and 87 kilowatt hours.

See also

Individual evidence

  1. ^ A b Hans-Günter Boy, Uwe Dunkhase: The master's examination in electrical installation technology . 13th edition. Vogel Buchverlag, Würzburg, 2010, ISBN 978-3-8343-3187-8 .
  2. ^ Hermann Wellers: Specialized examination in electrical engineering and energy engineering . 2nd revised edition. Verlag W. Giradet, Essen 1981, ISBN 3-7736-2791-2 .
  3. ↑ a b c d A. Senner: Electrical engineering . 4th edition. Verlag Europa-Lehrmittel, 1965.
  4. ↑ a b Ernst Hörnemann, Heinrich Hübscher: Electrical engineering specialist training in industrial electronics . 1st edition. Westermann Schulbuchverlag, Braunschweig, 1998, ISBN 3-14-221730-4 .
  5. ^ Günter Springer: Electrical engineering . 18th edition. Verlag Europa-Lehrmittel, Wuppertal 1989, ISBN 3-8085-3018-9 .
  6. ^ A. Grothe & Söhne GmbH & Co. KG, 53773 Hennef, DE: Bell transformer. Patent No. DE10045511A1 September 27, 2001 accessed on November 7, 2013.