An electrical supply is used to feed electrical equipment on a railway vehicle. This can be applied with different ac and dc supply voltages including different frequencies in the case of ac supply. Various convertors are available to do this. Transformers areused to reduce the voltage to items of equipment which are not frequency sensitive. For items which are frequency sensitive, frequency convertors are used. With do supply an dc/ac convertor is used directly or by electronic switching to give the desired frequency. A permanent magnet motor is used for this switching. Thyristor control is included.
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