Fault Signal Analysis for Aircraft Generator Rectifier

Integrated drive generator (IDG) connected with the main shaft of aircraft engine is the key power source for many electronic systems such as flight management computers, control and navigation systems, supplying constant frequency AC electrical power to the aircraft. IDG is composed of constant speed drive with differential assembly, brushless synchronous exciter generator, rectifier, brushless synchronous main generator, and generator control unit. The function of rectifier is to convert the alternating current from the exciter generator into a direct current, which will be applied to field winding of the main generator for producing three-phase voltage to aircraft electronic systems. According to report from previous research, diode failure in rectifier occurs with a high frequency. In this paper, we attempt to propose a solution for fast and accurately detecting faults from rectifier. We first analyze the noisy signals generated under different cases of diode faults by virtue of a simulated circuit model built in Matlab, and the fault signal is decomposed into finite intrinsic mode functions by empirical mode decomposition. Intrinsic mode functions are successively transformed by Hilbert transform to obtain the instantaneous frequency. Therefore, the fault transient signal can be analyzed by means of the instantaneous frequency and Hilbert marginal spectrum. The experimental results show that our method can be effectively applied to analyze the fault status of aircraft generator rectifier. Our work has potential to in real-time monitor safe and reliable operation of aircraft generators and further supervise the quality of aircraft power.