Advanced manufacturing process for ZnO surge arrester disks

In 1968, Dr. Matsuoka and his colleagues at Matsushita Electric Company discovered the devices which are now called metal oxide varistors. These materials, consisting of ZnO mixed with small quantities of bismuth and other metal oxides, can have extremely non-linear voltage-current behavior. Unfortunately, the performance of these devices is often limited by the mechanical powder mixing technology (e.g. ball-milling) typically used in production. Raychem has developed and scaled-up a chemistry-based manufacturing process for ZnO varistor powder. This new process, which eliminates all of the disadvantages of the conventional mixing processes, is described in comparison with the traditional methods. Some electrical performance characteristics of the surge arrester disks made from this powder are also presented.