Model Based Monitoring

Electrical machines are the core of industrial plants or power stations. Ensuring their continuous operation requires knowledge of a motor’s health and operating state at all times. Therefore, the requirements on modern monitoring and diagnostic methods for electric machines are very high. Methods are required which are able to detect incipient defects in an on-line fashion with sufficient foresight so that predictive maintenance can be done to avoid unscheduled downtime.

For motor monitoring purposes, the Department Mobility utilizes mathematical model-based methods to gain a deep insight into the health of machines. With a model-based method, motor states and parameters, which are difficult or costly to measure, are calculated. A model-based monitoring method can take into consideration the systematic dependencies of fault-specific quantities in an inherent way through the calculation of several parameters of state. This characteristic enables the monitoring of drive systems in stationary as well as in dynamic operating conditions.

The Vienna Monitoring Method (VMM) can be used with asynchronous machines with squirrel cage rotors or slip-ring rotors. It has been shown that the established error indicator is independent of speed, load torque, moment of inertia, voltage supply, and size of the machine. Therefore, this method is particularly suitable converter-fed machines, since its effectiveness is independent of the particular motor control system. The advantages of model-based monitoring are,

• Reduction in downtime due to a reduction of drive failures
• Monitoring is possible during the operation of the machine (no disassembly of the machine or downtime is required)
• State of the machine is recordable at any time
• Service intervals are dependent on the state of the machine – condition-based maintenance as opposed to time-based maintenance
• Continuous determination of the state allow for conclusions to be drawn on the residual operating life of the machine