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R. Wieser, C. Kral, F. Pirker, M. Schagginger:
"High Sensitive Rotor Cage Monitoring During Dynamic Load Operation, the Vienna Method";
Talk: ICEM, Istanbul, Turkey; 1998-09-01; in: "International Conference on Electrical Machines ICEM'98,", (1998), 1.

This paper suggests a method for the detection of faulty rotor bars in the squirrel cage of an induction machine. The proposed Vienna Monitoring Method compares the calculated torques of two on-line models, and takes thus the load state into account. In case of a rotor asymmetry, the different model structure and input quantities yields to a torque difference, which is even detectable for an early extend of fault. This monitoring technique can be applied for both, stiff voltage supply and the very high noise level of an inverter fed induction machine, independent of the utilized control procedure. As the calculated torque difference is evaluated in a rotor fixed reference frame, the Vienna Monitoring Method works independent of speed within a wide range. There, a faulty rotor bar can be detected reliable not only with steady state load but also under speed transient conditions without a clutched load.