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Pictures of the Future


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Pictures of the Future
The Magazine for Research and Innovation

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Simulation Model Keeps Motors Safe

Researchers with a demonstration model for measuring motor temperatures.

Excessive temperatures can damage electric motors. A new simulator monitors operation and notifies users if a motor is approaching its temperature limit, thus opening the door to longer operating times.

Electric motors can be damaged if they overheat. This is particularly true for large drives, whose rotors are subject to high thermal stress when they are switched on. That’s why the temperature of rotating rotors needs to be kept under control. But because it’s very difficult — or even impossible — to take such measurements, instruments from the digital bag of tricks are being used to help solve the problem.

Large drives can now be utilized more effectively thanks to a new simulator that predicts their interior temperature. The drives in question are salient-pole motors — big machines used in the gas, oil, and chemical industries that are often used to pump large volumes of liquids. When such motors are switched on, they briefly generate lots of heat. If they were turned on several times in rapid succession, their interior temperatures would soon reach such high levels that they would be damaged. That’s why large drives have to cool off for a whilebefore they can be switched on again. Because the temperature in critical areas within a motor can’t be directly measured, the length of time a machine has to cool off can currently only be estimated. Experts generally incorporate a safety margin to ensure that a drive isn’t damaged. Often, the machines are cooled off for about 12 hours — much longer than is actually necessary. Associated financial losses for operators are considerable.

But help is now on the way, thanks to a new simulator developed by Siemens Corporate Technology. During a motor’s operation, the new system calculates the motor’s temperature as precisely as direct measurements would. As a result, operators can precisely calculate cooling times.

Temperature development of the demonstration model. A simulator calculates temperature development in real time (green curve). The blue curve forecasts how the temperature will develop in the future if the motor continues to be operated at the same load after it is turned on.

Hands-on Demonstrator

A table-size demonstrator shows how the simulator works. The system contains a shaft that links two small electric motors. The left-hand motor brakes the right-hand one to generate a continuous load. While sensors measure the temperature on the motor’s exterior, the system also records data about the operating period and the load. The simulator uses these input parameters and a mathematical model of the motor to calculate the temperature inside the right-hand motor and forecast how the temperature will continue to develop

Combining Engineering Know-how with Smart Data

The special feature of the simulator is its rapidity, which enables it to show how the temperature is developing in real time. This is made possible by many years of engineering know-how, which is expressed in mathematical motor models that are used during a motor’s development and that precisely take the motor’s geometric properties and materials into account. However, these models are so extensive and complex that they normally can’t be used for real-time calculations. Researchers at Siemens have now managed to use mathematical reduction methods to create abstract models that are less comprehensive but still sufficiently meaningful.

Aenne Barnard