Interference suppression on motor connection cables for frequency converters

It is a fact that frequency converters that operate asynchronous AC-motors are an inherent source of conducted and radiated interference. This attributes to the short pulse rise time of the modulated output voltage of the converter. Because the converter itself cannot be changed, the suppression of the interference is possible only through external means. For this reason, broadband inductive filtering is generally used to suppress the voltage peaks on the motor. Normal industry practice is to use a conventional shielded cable in conjunction with the prescribed EMI-filter to reduce the conducted and the radiated interference. When this conventional cable is substituted with a shielded ferrite layered low pass cable, the difference in the level of reduction is dramatic. The low pass ferrite coated cable assures a suppression of the asymmetric current and significantly reduces the interference emission. The comparison of a conventional shielded cable to the low pass ferrite coated cable is presented and described