A Suitable Method for Ecovehicles to Control Surge Voltage Occurring at Motor Terminals Connected to PWM Inverters and to Control Induced EMI Noise

A method that is suitable for ecovehicles, which controls the surge voltage appearing at motor terminals that are connected to a pulsewidth modulation inverter with short leads that are less than the critical cable length (i.e., the shortest length at which full reflection may occur), is described here. Also, a method to control electromagnetic interference (EMI) noise, which is induced by the surge voltage, is discussed. Ecovehicles have the problem where insulation degradation of motors occurs due to the surge voltage being repeatedly applied to motor terminals during long lifecycles. EMI noise such as the shaft current and the radiated noise, which are induced by the generated surge voltage, easily diffuse into other electric devices due to the high-density packaging structure. The diffused EMI noise may cause a malfunction of the vehicle controller. An EMI noise controller is studied, which can meet the high-density packaging requirements for ecovehicles like electric vehicles. The EMI noise controller is attached on the motor terminals and simultaneously suppresses the surge voltage and the noise. After clarifying surge voltage characteristics and a circuit model for expressing the surge phenomenon through experiments and simulations, an EMI noise controller is proposed, which uses a multilayer printed power circuit technique. It is verified through simulations and experiments that the proposed controller has the ability to simultaneously control the surge voltage and the EMI noise, such as the radiated noise and the shaft current (the bearing current), which are induced by the surge voltage.