The Vienna induction machine monitoring method; on the impact of the field oriented control structure on real operational behavior of a faulty machine

Rotor cage asymmetries cause disturbances of the flux pattern in induction machines. These nonuniform magnetic field components affect machine torque and stator terminal quantities and are thus detectable by monitoring systems. However, the impact of minor machine asymmetries on the overall machine behavior is quite small. This makes the separation of the fault specific signals out of commonly distorted measurement quantities a challenging task. In order to schedule maintenance, faults should be detected at an early state of growth. Thus, any monitoring method should be very sensitive. The proposed “Vienna Method” fulfils both excellent noise immunity and high sensitivity. Simulation and experimental results from an industrial IGBT drive verify the validity of the approach and its superior properties. The technique is based on real time machine models. Up to now these models have been used for advanced machine control purposes only. However, the comparison of the two machine models outputs permits an insightful analysis of the faulty machine behavior too. Out of the knowledge of the model interaction with machine asymmetries the conjunction of the control structure with the real operational behavior of the machine can be concluded. This is due to the fact that the on-line machine models also form the basis for machine control. In the paper the induction machine behavior is investigated for constant volts per hertz control as well as indirect and direct field oriented control