Experimental evaluation of damper circuit influence on the performance of multiphase synchrnounous generators feeding multiple rectifiers

In today's power generation systems, driven by variable-speed prime movers and feeding DC or fixed-frequency grids, the output power of the alternator needs to be rectified. The presence of output rectifier bridges causes a significant distortion of phase currents. This paper investigates the role played by rotor damper circuits in limiting the effects of such distortion. The investigation is extended to the case of multiphase alternator arrangements suitable for supplying a different number of output rectifiers. The study is conducted through tests on an alternator prototype which has been operated with two kinds of rotors, one with and the other without damper circuits. Testing results show that the influence of dampers is significant only in the case of generator three-phase winding and single output bridge.