Measurements of spectral distribution of EMI emissions from adjustable speed drives of induction motors

Adjustable speed drives (ASDs) are widely used in office buildings, hospitals, private residences, and modern electric vehicles. The electromagnetic interference (EMI) noise produced by ASDs may affect proper operation of various electronic systems. At the University of Wyoming, an intensive study of EMI emissions from ASDs has been completed. A system under test (SUT) assembled for this work included a commercially available ASD made by the ABB Industrial Systems Inc. that drove a 45 kW 3-phase induction motor loaded to 75% of its maximum power. Four main sources of EMI produced by the SUT have been identified. EMI of the SUT has been measured in the frequency range 30 Hz to 1 GHz under several grounding and shielding options. Main results of measurements are reported in this paper.