Winding Configurations for Five-Phase Synchronous Generators with Diode Rectifiers

Wound-field synchronous generators are widely used in aircraft and marine electrical systems. As the electric power requirements increase, there is renewed interest in dc power networks, but the electrical source remains a synchronous generator. The combination of a diode rectifier with a wound-field multiphase generator reduces the voltage ripple on the dc network and increases fault tolerance, compared with an equivalent three-phase system. It also increases the options in terms of the winding design and configuration. This paper uses circuit modeling, including harmonics, informed by static finite-element results, to understand the wound-field generator performance for star and polygon connections of both short- and fully-pitched coils. Experimental results are used to validate the models. A polygon connection of short-pitched coils is shown to give good generator utilization for a healthy machine. However, careful design is required to prevent circulating harmonic currents. Under winding open-circuit faults, the polygon connection requires significant derating, making the star connection the preferred option.