Effects of excitation controls on operation of synchronous motors

The control of field excitation of a synchronous motor affects its operation, system voltage regulation, stability and utilization of the leading reactive power output. An excitation system may permit removal of the excitation when motor pulls out of step and reapplication for automatic resynchronizing. Earlier unregulated excitation systems have been replaced with microprocessor-based static excitation controllers that integrate protective functions and provide online control of the excitation. The paper discusses the excitation systems, of the brush and brushless types, from considerations of motor starting, running, stability, reactive power compensation and voltage regulation