General principle for brushless synchronous machines and its application in an invertor-fed drive

Rotor excitation of brushless synchronous machines may be obtained by a process of induction and rectification. Various embodiments of this principle are discussed briefly, and the paper then concentrates on one particular form in which the harmonic voltages of a thyristor-invertor output are harnessed to produce d.c. excitation of a 3-phase wound rotor. Test results are given for an experimental drive that yielded very good synchronous performance. A theoretical analysis of the system has been developed, and computed results agree closely with the tested characteristics.