Shunt generator

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Shunt
excitation (self-excitation)

The design of an electrical generator in which the excitation winding ( field winding ) and the armature (armature winding) are connected in parallel is referred to as a shunt generator .

description

Schematic representation

Since the excitation winding and the armature form a parallel circuit, the shunt generator adapts much better to changing loads because only part of the armature current is branched off for field development. If the armature is driven from standstill, a low voltage is generated in it if there is still residual magnetism (remanence). The residual magnetism is increased by a small excitation current if the excitation winding is connected correctly. This creates a greater tension. This principle enables the machine to excite itself. However, if the excitation winding is connected incorrectly, the residual magnetism is weakened by the excitation current and the machine cannot excite itself - even if the armature terminals are short-circuited. If the voltage is to be adjustable, a field regulator is connected to the excitation circuit . This can be realized by a rotary resistor or a sliding resistor . If the excitation circuit is opened, a large voltage is induced in the excitation winding, since the excitation current changes very quickly. In order to prevent the resulting damage to the winding insulation, the field winding is also short-circuited via a terminal on the field regulator when the field circuit is open.
In contrast to the separately excited generator, the voltage at the armature terminals drops more sharply than the no-load voltage under load . The resulting small voltage drop at the armature resistance causes a reduction in the field winding and the voltage also drops. So that the residual magnetism is not weakened when the direction of rotation is reversed, the current must flow in the field winding in the same direction. To do this, the polarity of the armature or the field winding must be reversed. Since no external excitation is necessary with a self-excited generator , this does not apply here.
There is also a combination of a shunt generator and a main circuit generator (series generator ), which is called a double circuit or compound generator.

example

A DC alternator is a shunt generator. About two brushes is the collector of the drum anchor a smoothed DC voltage decreased.

See also

literature

  • Hans-Ulrich Giersch, Hans Harthus, Norbert Vogelsang: Electrical machines. Testing, standardization, power electronics. 5th edition. Vieweg + Teubner Verlag, 2003, ISBN 3519468212 , pp. 114/115, 120/121, 124–126 ( limited preview in the Google book search).
  • Herbert Bernstein: Electrical engineering / electronics for mechanical engineers. Vieweg + Teubner Verlag, 2004, ISBN 3528039698 , pp. 293/294, 295, 356 ( limited preview in the Google book search).
  • Karl Küpfmüller, Wolfgang Mathis, Albrecht Reibiger: Theoretical electrical engineering. An introduction. 18th edition. Springer Verlag, 2008, ISBN 3540785892 , p. 482 ( limited preview in Google book search).
  • Gerd Fehmel, Peter Behrends: Electrical machines. The master's examination. 13th edition. Vogel Buchverlag, 2004, ISBN 978-3-8023-1981-5 , p. 232 ( reading sample: DC generators - mode of operation ; PDF file, 1.15 MB.).

Web links