An effective instrumentation system of eliminating common-mode effect induced by PWM inverter

An acquisition system centred on Rogowski coil and the voltage divider is introduced to eliminate the common-mode voltage effect induced by the H-bridge PWM inverter. The test apparatus is made of the voltage measurement, the current transducer, and the Nicolet acquisition system. For reducing the common-mode influence, a symmetrical voltage divider circuit is proposed by the instrumentation, which has a fast speed of analyzing the voltage and current in real time. And the fundamental current and the fundamental voltage and their phase-angle difference are gained accordingly by means of the Fourier transformation. Both theory analysis and experimental results can verify the feasibility of the proposed instrumentation system.