Brushless Alternator with Optoelectronically Controlled Rotating Thyristors

The paper describes a brushless alternator arrangement in which the conventionally used rotating diodes are replaced by thyristors. To preserve the brushless principle, the firing signals are transmitted optically from a stationary source to a single shaft-mounted light-sensitive diode, which feeds a simple transistorized amplifier and a decoding circuit. Light pulses to the diode are coded in such a way that each thyristor is addressed in an appropriate sequence with a firing signal. The considerable improvement brought about by the new excitation system is illustrated by a comparison of the transient performance of a 10 kVA alternator, when excited by conventional and by rotating-thyristor means.