Failure Analysis And Fault Diagnosis System For Air-conditioned Passenger Compartment's Inverter

As an important part of air-conditioned passenger compartment, the inverter plays an important role in guaranteeing safe operation and providing comfortable environment for passengers. With the fast development of railway passenger market, the inverter is widely used, but the working circumstances are quite unfavorable for inverters, such as humidity, high temperature, strong mechanical shock, over-voltage and over-current, which result in high failure ratio of inviters. Therefore, the automation and intelligentization of the inverter's fault diagnosis has become an imminent requirement. First, this thesis analyses failure reasons and failure modes of inverters so as to choose adequate signal acquisition points and to specify the failure reasons of inverters. The fault diagnosis system consists of two parts: the signal acquisition subsystem and the fault diagnosis subsystem (host PC). The two parts exchange data via RS-232C serial communication. Digital signal process technology is applied to fault diagnosis in the signal acquisition subsystem. Digital filters are designed to reduce the noise. FFT method is adopted for calculating frequency spectrum, which is used to analyze the output quality of an inverter. A Window is used in FFT. In this way, the working states of the inverter can be recognized and its performance can be evaluated. A production rule based expert system is developed for the inverter fault diagnosis. After broad survey on theoretical literature and accumulation of maintenance staff's practical experience, we built the base of rule knowledge in modules. Enumerating method and forward reasoning are used in the expert system to find a matching rule. The host PC software is developed with C++ Builder 6.0 under Windows 2000 Operating System. The main functions of host PC software are to report the fault diagnosis results, display all kinds of signal curve graphics and show frequency spectrum of the inverter's outputs. The field tests prove that this system can monitor online effectively, and its reports can provide useful information for the inverter's maintenance. With friendly human-machine interface, users can operate it easily.