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Nowadays, electric machines are often driven by power electronic converters. Even though the use of converters brings with it a variety of advantages, common mode (CM) signals are a frequent problem in many installations. Common mode voltages induced by the converter drive common mode currents damage the motor bearings over time and significantly reduce the lifetime of the drive.
Hence, it is essential to measure these common mode quantities in order to take suitable countermeasures. Handheld oscilloscopes in combination with Rogowski probes offer a simple and reliable way to accurately determine the required quantities and the effectiveness of different countermeasures.