Static excitation device

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Slip rings and carbon brushes of a synchronous generator in the Amsteg power plant

The static excitation device is an excitation system for synchronous machines . The term static refers to the fact that the device consists of fixed parts, such as B. the excitation transformer.

construction

SG : three-phase synchronous generator; ET : excitation transformer; V1 : thyristor actuator; I E : excitation current.

The static excitation device, unlike the brushless , does not require any co-rotating excitation machines , but has an excitation transformer that is fed from the stator circuit of the three-phase synchronous generator or an internal supply network. The excitation transformer transforms the applied voltage from the stator circuit or the internal supply network to the required excitation voltage and feeds the excitation winding of the three-phase synchronous generator via a line-commutated thyristor actuator. The transmission to the excitation winding takes place with carbon brushes and slip rings . In large generators , because of the high excitation currents, many carbon brushes are connected in parallel and the slip rings have to be very wide. A de- excitation circuit can be implemented in the excitation circuit , which is advantageous in the event of an internal machine fault.

Advantages and disadvantages

advantages

  • Since the excitation power is controlled directly via the thyristor control element and not indirectly via the auxiliary excitation power of the exciter as is the case with brushless excitation, static excitation is the most advantageous method in terms of control technology . It offers a high level of dynamic control.
  • Maintenance of slip rings and carbon brushes possible during operation
  • Fast de-energization possible
  • Frequency ramp-up possible with start-up inverter

disadvantage

  • Brush and slip ring losses and brush wear
  • Brush fires and high brush wear can occur if the current distribution of the brushes connected in parallel is disturbed. This can be caused by the wrong number of brushes as well as by climatic conditions.
  • no use in Ex-protected areas

literature

  • Rolf Fischer: Electrical machines. 14th, updated and expanded edition. Carl Hanser Verlag, Munich 2007, ISBN 978-3-446-41754-0 .
  • Adolf J. Schwab: Electrical energy systems: Generation, transport, transmission and distribution of electrical energy 2nd, updated edition. Springer Verlag, Berlin 2009, ISBN 978-3-540-92226-1 .
  • Christof Lechner and Jörg Seume: Handbook Stationary Gas Turbines (VDI book) 1st edition, Springer Verlag, Berlin 2009, ISBN 978-3540428312