Improvements in EMI performance of inverter-fed motor drives

Measurements of conducted radio-noise emissions from a commercial PWM inverter with an induction motor are presented. It is determined that the common mode emissions predominate the noise level and the spectrum components in this type of system, which result from the derivative of the line to ground voltages at the main circuit (dv/dt) and the circuit parameters, consisting of the physical stray inductance of the main circuit conductors and distributed capacitance formed between the circuit conductors and the grounded chassis/frame, most of which concentrate in motor windings and power-semiconductor devices in this system. Modeling and simulations of the system for purpose of evaluation of EMI are presented. Several strategies suppressing conducted radio-noise emissions are proposed, which are practically feasible for cost-effective EMC designs. Both the simulation and experimental results demonstrate that high level radio-noise were significantly suppressed and the EMI performance of the system are able to meet the CISPR and FCC limits on conducted emissions for digital devices.<
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