Diode rectification of multiphase synchronous generators for aircraft applications

Increased electrical loading on aircraft power systems has led to interest in DC electrical networks for aircraft applications. This paper investigates a wound-field synchronous generator and uncontrolled diode rectifier as the DC source and analyses the power quality of the AC and DC sides of the rectifier. The paper gives expressions for voltage and current distortion for a multiphase generator as a function of the number of phases. For a star-connected machine, the power quality on the AC side is shown to deteriorate rapidly as the phase number increases, resulting in increased losses and a higher rating requirement. A delta connection provides better utilisation of the generator; however, at the expense of the fault tolerance. Mathematical models for the multiphase system are developed and the analysis is supported by simulation results; verified through laboratory testing.