The use of a knowledge-based system in power electronic circuit fault diagnosis

The diagnosis of faults on electronic equipment requires the provision of monitoring outlets. To avoid expensive additions to existing circuits or to well-integrated designs, monitoring of only input and output quantities is preferable. To determine the location of an internal fault, a reasoned diagnosis is required and a knowledge-based system provides an automatic method of carrying out the reasoning process. Three-phase power electronic inverters have similar configurations of switches and thus can be treated in a more standard form than can other electronic circuits. A commercial inverter has been tested under normal conditions and with specific faults created. The results have been compared with those obtained from two alternative simulation methods. From the slightly differing results, ranges of uncertainty of parameter values have been obtained and the results have been used to create a rule base for a proprietary expert system environment. The work is described at an intermediate stage in an ongoing programme