Control methods for EMI noises appearing in electric vehicle drive systems

This paper describes control methods for EMI noises appearing in EV drive systems and radiations induced on the body frame of EV's by them. The methods are proposed through experimental and theoretical analyses of EMI noises appearing in the EV drive systems. The analyzed results show that there are two kinds of EMI noises in EV drive systems. One is differential mode noises appearing due to series resonance phenomena in the DC circuit between batteries and inverters at the time of switching operations. The produced noises are diffused into the body frame via stray capacitors between the inverter and car body frames as a common mode current. The other kind is EMI noises caused by surges appearing at motor terminals. They cause another common mode current that diffuses into the body frame via the motor shaft. The surface currents appearing on the body frame through these diffusion processes induce radiations around the body frame which cause electromagnetic interference between EVs. One method is proposed that controls differential mode noises including radiations induced by them; it uses a multi-layer printed power circuit technique. Another method is proposed that prevents radiations induced by the common mode current produced due to surges occurring at motor terminals by suppressing series resonance phenomena occurring in common current paths. It was verified from simulations and experiments that these methods controlled EMI noises including radiations which appear in EVs.