Use of low-pass filters to protect equipment from transientovervoltages on the mains

摘要

The design of commercial low-pass filter modules for equipmentconnected to the low-voltage supply mains is reviewed. Problems of usingthese filters to protect electronic equipment from damage or upset byhigh-voltage transients on the mains are discussed. The design andperformance of circuits that incorporate both overvoltage protection anda low-pass filter are discussed. One circuit is designed for commercialenvironments, the other of medical equipment in patient care areas.Filters for medical equipment in patient care areas must have very smallline-to-ground leakage currents, which make it difficult to provideeither overvoltage protection or low-pass filtering. Using anovervoltage-protection low-pass filter is less expensive than using aline conditioner to protect equipment, and, in many instances, thefilter may give satisfactory protection