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T. Wolbank, R. Wöhrnschimmel, P. Macheiner:
"'Detection of faults in inverter fed ac machines without phase current measurement";
Vortrag: International Conference on Electrical Machines, Brugge, Belgium; 25.08.2002 - 28.08.2002; in: "Proceedings ICEM International Conference on Electrical Machines", (2002), ISBN: 90-76019-18-5; S. 449 - 454.

In this paper a new method is presented which enables a very sensitive detection of asymmetries in inverter fed ac machines with a reduced amount of sensors. The asymmetries may for example be caused by a stator winding isolation fault or by rotor eccentricity. The method is based on the transient electrical behaviour of the machine. As the evaluation algorithm has been kept simple, the whole detection scheme can be integrated into a simple current control structure. In addition, the method only needs information about the DC link voltage and current. The method is applicable in steady state as well as transient operation and in the whole frequency range of the drive. It is based on a comparison of the transient electrical parameters of the individual phase windings. The necessary transient excitation of the phase windings with voltage pulses is realised by the current control loop during normal operation. An asymmetry or a fault condition is detected and located by comparing the parameters of the three adaptive phase current observers. The method is thus insensitive to changes of the machine parameters due to temperature or saturation as these changes occur mainly symmetrical. Measurement results at different points of operation and different faults are presented to show the applicability of the method.