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.