Controlling methods of EMI noises generated in motor drive systems

The paper describes methods that control EMI noises generated in power converters (rectifier and inverter) by using power printed circuit techniques. Two kinds of differential and common mode noises are generated in the motor drive system. A method is proposed that controls the differential mode noises by symmetrically forming the structure of the positive and negative power transmission lines of the power converter using a four-layer printed power circuit technique. Simulations done using the method show that differential mode currents appearing between the terminals of the power converters and the smoothing capacitors can be almost completely eliminated and the common mode currents are shunted into the artificial ground plane. Another method is also proposed that controls the shunted common mode currents so as to prevent series resonance phenomena by inserting a damping impedance between the frame of the machine and the ground. Experiments verify that the common mode currents generated in the motor drive system can be effectively reduced by the two proposed methods.