Design and performance of surge suppressors

The author discusses some of the considerations in the design and construction of surge suppressors and how they affect the performance of the suppressor. Emphasis is given to voltage protection level or clamping voltage, explosion or fire hazards, use of thermal cutouts to disconnect a failing varistor, welding of circuit breakers by surge currents, failure indicators, excessive leakage current, and advertising hyperbole. Tests on more than two dozen different models of commercially available surge suppressors during 1987-1990 showed that some types of suppressors perform much better than others. Sometimes there are potentially serious defects in the design or construction of the suppressors. The manufacturer´s specifications and UL clamping voltage rating are often not consistent with laboratory measurements. It was found that many of the advertising claims made for commercial surge suppressors are exaggerated. Design defects were found in surge suppressors manufactured by large, well-known companies. Therefore, purchasing a well-known brand offers the user no assurance that the suppressor is good