Computerised fault diagnosis of induction motor drives

In spite of the fact that the probability of breakdowns of 3-phase induction motors is very low, 2 to 3% per annum, monitoring their operating condition is essential, particularly when they are working in sophisticated workshops (for example automated production lines). In many industries lots of machines depend on mutual operation, and the cost of unexpected breakdowns is very high. In such cases the breakdowns of machines in operation usually involve higher losses in the production process than the cost of their repairs or even the initial costs of the machines themselves. In addition to the faults, i.e. short circuits, winding failures, bearing seizures, causing an immediate stop in the production process often has safety implications and may even expose human beings to danger. Both technical and economical considerations suggested the development of a new computer-based diagnostic system to predict the dates and places of expected faults by condition monitoring. The computer-based measurement and analysis system was designed and tested under a cooperation scheme between the Middlesex University, London and the University of Miskolc, Hungary. This system, after analysing various quantities of the drive unit, predicts the possible breakdowns, their expected dates and places. The authors discuss the criteria for a new diagnostic system, and then describe the hardware and software of the new system