The Aircraft Power Supply System Distortion Parameters Tests

Aircraft electric power supply systems play an important role in flight of modern airplane. The measurements of AC and DC voltage distortion parameters play an important role in various parameters test of aircraft electric power supply systems , it needs to be tested accurately. So in this paper, a thorough research of distortion parameters test methods for aircraft power supply system is discussed and analyzed according to GJB 181A-2003 and MIL-STD-704E, furthermore, a distortion parameters test system which is based on Virtual Instruments (VI) is proposed.Firstly, methods and theories of testing distortion parameters are discussed and analyzed in this paper; the arithmetic of DFT and FFT are discussed, the error reasons are founded, the arithmetic of interpolated FFT and using double windows function are used in order to improve FFT. Secondly a detailed system hardware and software design method is proposed. The hardware part is based on PXI bus, and the data can be acquired though the data acquisition card—PXI-6254, which is a new product of NI Company, and can be transferred by MXI-4 bus, in the same time, a detailed design method of modulating circuits is given in this paper. The software part uses the graphics program language Lab VIEW that is produced by NI Corporation as VI's application platform. According to characters of the distortion spectrums, digital filters which are based on various frequency location and the method of signal decimation and Lab VIEW software language are used to solve the measurements of distortion spectrum for AC and DC voltage. Finally, through experiments it can be concluded that the software of data processing and overall test system meet basic accuracy requirements.