Investigation on Diagnostic Methods of Rotating Machines and Influence Factors Based on Existing Testing Products

Abstract: This thesis summarizes established methods for electrical diagnostics of the insulationof large rotating electrical machines, i.e. generators and large motorsworking above the low-voltage range. It then investigates the possibility ofusing some existing diagnostic instruments, not specically intended for machineinsulation, for performing standard tests on a certain type and range ofthe rotating machines. The summary of general diagnostic methods for rotatingmachinery includes the traditional methods and currently used methodsin industry. It considers what types of the defects can be detected, and theinuence of the applied voltage magnitudes and frequencies, etc. Then thereis a literature study of several recent or developing technologies such as on-linemonitoring and frequency response analysis, to investigate the possible futuredevelopment of the diagnostic methods that have practical applications duringmanufacturing and operation of rotating machinery for a more accurateand timely assessment. Possible modications to testing devices to suit themmore to machine insulation are investigated. A study of three market-existingdevices summarizes the machine diagnostic tests that they could be used for.Finally, an experimental study on a stator coil rated 7 kV is reported, and itsresults are used to analyze the inuence of the test factors such as frequencydependency, for future investigation.