Excitation cct for brushless sync motor - has single auxiliary thyristor controlling main rectifier thyristor firing

摘要

The brushless synchronous motor of the parent patent (2408553) is improved by adding a single auxiliary thyristor rectifier (9) in series with the auxiliary resistor (5) between the main thyristor gates and the neutral of the exciter winding (2). The need for additional control circuitry across the exciter windings is thus removed. During the run-up the auxiliary thyristor is off and the bridge is non-conducting. At the correct instant during the run-up the control circuit (10) is activated and the bridges begins to operate to excite the motor field. Suitable control circuits may be used as specified in the parent patent.