Introduction to Conducted Emission in Adjustable Speed Drives

Switch–mode power conversion methods are increasingly being used in many of contemporary applications. This is because of their evident advantages and rapid development of power electronic switching devices which allow to improve efficiency of power conversion. Use of faster switching power electronic devices induces generation of rapid changes of voltages and currents which are unluckily to be the sources of electromagnetic emission in a wide frequency range. Adjustable speed drives (ASD) that are composed mainly of a power electronic static frequency converter (FC) and an AC motor are one of the most common applications in contemporary power systems with relatively high electromagnetic emission levels. The extremely high electromagnetic emission of ASD's results in electromagnetic compatibility (EMC) violations in many installations. The wide frequency spectrum of electromagnetic disturbances (EMD) generated in ASD causes that their propagation in local installations and throughout the whole power system becomes relatively easy and effective, even over long distances. Easiness of EMD propagation in power systems results in the necessity of electromagnetic emission limitation to maintain undisturbed operation of various devices and systems used in a shared electromagnetic environment.