An active common-mode filter for reducing radiated noise from power cables

Power electronics equipments can cause serious electromagnetic interference (EMI) because of their high-speed switching. Such switching disturbances then propagate along power cables, which can act as antennas to radiate the noise. Typically, a passive filter composed of inductors and capacitors is widely used to reduce electromagnetic interference. However, when a power cable is connected to the passive filter, the cable acts as a distributed line that worsens the attenuation characteristic of the passive filter at the anti-resonant frequencies of the cable. This paper proposes a solution to this problem in the form of an active common-mode filter (ACF) that uses a high-speed amplifier. Experimental results show that the proposed filter improves the attenuation characteristics of the passive filter and reduces the common-mode voltage propagating through the cable over a wide range of frequencies from 10 MHz to 100 MHz. Furthermore, measurements for radiated noise from the cable are carried out in an anechoic chamber, and evaluate the radiated noise attenuation characteristics of the ACF.