Electric Power Research Institute Incorporated

Robert G Johnson

Kenneth C Radford

Andrew S Sweetana, Jr

A method of manufacturing a varistor utilizes preselected amounts of ZnO which are combined with specified amounts of additives including B, Na, Bi.sub.2 O.sub.3 and BaO to form a variety of compositions. Each composition is pressed into a disc. The disc is then sintered at a first selected temperature. Afterwards, the disc is annealed at a second selected temperature. The specific compositions disclosed render a varistor with improved high temperature performance when the annealing step is followed with a low temperature tempering cycle at approximately 250.degree. C.

Surge stability improvement of zinc oxide varistor discs

A method for producing varistors having high energy absorption. The high energy absorption is achieved by combining predetermined quantities of Bi.sub.2 O.sub.3, BaO, SiO.sub.2 and Sb.sub.2 O.sub.3 with ZnO to produce a mixture which is sintered to produce a varistor disc having high energy absorption.

High energy absorbing varistor

A varistor utilizing a disc of mainly ZnO in combination with preselected combinations of Bi.sub.2 O.sub.3, Sb.sub.2 O.sub.3, SiO.sub.2, MgO and CaO.

Very high energy absorbing varistor

A method for making a varistor disc with increased high temperature stability. The method includes the steps of formulating a mixture for the varistor disc, compacting the mixture to form a disc, sintering the disc at a first preselected temperature and cooling the disc at a predetermined linear rate. The predetermined linear rate and preselected temperature are selected to reduce nonequilibrium conditions which become 'frozen-in' as said disc is cooled.

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Bloomington, IN, United States of America

Robert G Johnson