D07.10 - Simultaneous Measurement System of Differential Mode and Common Mode Currents Without Influence for Radiated EMI in Three-Phase Variable Speed Drive System

This paper presents problems and solutions in a simultaneous measurement for radiated electromagnetic interference, and differential-mode and common-mode currents. In the high frequency range, the currents are small magnitude, which reduces the measurement accuracy due to the resolution of the measurement equipment. In addition, the couplings between the equipment under test and the measurement system are significant in the high-frequency range, which also deteriorates measurement reproducibility due to the coupling currents flowing through the coaxial cables. Thus, the simultaneous measurement techniques are established by using high-pass filters and amplifiers to increase measurement sensitivity, and by adding ferrite cores and arranging the layout of the measurement equipment to improve measurement reproducibility. The validity of proposed measurement techniques is experimentally verified using a three-phase AC/DC/AC variable speed drive system.