34 Motor Testing
Putting motors through their paces Mathis Menzel, CEO of Menzel Elektromotoren, discusses load testing and temperature rise testing of large electric motors and entire drive systems. He looks at the benefits of different test methods and how testing can contribute to efficient commissioning and operation.
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otor testing might be required for a variety of reasons. In the first instance, it offers a way to verify data. Motor manufacturers can identify limitations, weaknesses, and performance reserves of products. Notified Bodies use test services because they need to verify data independently, while motor users can check whether their motor or drive system meets their specifications. In addition, testing can also be used for troubleshooting and for parameterisation. For motor manufacturers, testing is generally the most appropriate way to see ‘how far can we go’ and which solutions are possible. For example, during type testing, it might be questioned whether a motor designed for continuous operation at a certain rated output can also drive another application with a slightly smaller load, with intermittent operation, and if so, what cooling periods are required? Or, might different or more powerful cooling solve a performance issue? Testbed operation offers a safe setting for load and no-load runs. Drive systems can be tested even with extreme parameters, such as severe short-term overloads, voltage drops, or various duty cycles or other non-standard situations during operation.
Load testing creates a very broad database about the tested equipment, and this can be very useful to answer questions at any later stage when the equipment is in the field. For example, the mechanical output is ensured with tested efficiency points, and so the mechanical input for the driven machine is also ensured. DATA QUALITY Conventional tests with a direct coupled load usually just show that the motor works properly on load. The efficiency values from such a setup will be guesswork. Menzel uses a slightly more sophisticated setup that allows calibrated measurements and produces high-quality information on the actual efficiency ratios. The exact input current is measured with current and voltage transformers. A torque measurement shaft installed between the motor and load measures the generated torque. Losses and efficiencies are calculated from the difference between the (electrical) input power and the (mechanical) output power. With the tested motor and the load generator operated in a closedloop, this setup only consumes power for startup and any energy loss. Therefore, supply lines do not have to be over-dimensioned, and energy-saving tests
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The manufacturer’s digital offer includes live streaming of motor tests to customers and a virtual tour of the test field on the website.
Quarter 2 2021
www.theaemt.com
