Analysis and Utilization of Common-Mode Voltage in Inverters for Power Supply

Common-mode voltage (CMV) exists at the terminal of motor windings when fed by voltage source inverters under pulsewidth modulation. For a long time, researchers devoted much effort to suppress or eliminate the CMV. From the perspective of energy utilization, this article proposed a method of powering the load by collecting the energy of CMV. This article derived the common-mode equivalent circuit, discussed the factors that affect the CMV power capacity, and quantitatively analyzed the maximum power transmission of CMV. Moreover, a compensation method with a resonant capacitor was proposed, which can increase the power capacity of CMV to more than two times of the original power output in the experiments. In practical applications, the method provided an auxiliary source inside the motor to power a 2 W motor encoder or even a monitoring system, which replaced the original power supply cable connected to the inverter. Furthermore, the influence brought by the proposed method on conducted EMI and stability issues of the motor drive system were evaluated. Experimental results validated the accuracy of quantitative analysis and effectiveness of the proposed method.