Investigation of relation between switch timing difference and common-mode voltage on cable

Recent equipment uses many inverters from the viewpoint of energy saving. The inverter circuits have a potential of disturbance source because the high voltage and high speed switching devices are used in the circuits. In this paper, we investigated the relationship between the switch timing difference of inverter circuit and the common-mode voltage on the cable. First, we investigated the mechanism generating the common mode voltage by using the inverter system which was used for driving a three phase motor. A simple equivalent circuit of the system was created. And then, the mechanism was evaluated by the circuit simulation. The results showed that the switch timing difference caused the common-mode voltage. Next, the drive circuit was constructed by using CPLD, and the common-mode voltage was measured by capacitive voltage probe (CVP). The results showed that the common-mode voltage increased by the increase of the switch timing difference and the influence mainly appeared below 1 MHz.