Zinc Metal Oxide Varistor Blocks For Surge Arresters, Used For DC And High Gradients

Zinc Metal Oxide Varistor Blocks For Surge Arresters, Used For DC And High Gradients

Zinc oxide Varistor is voltage dependent, nonlinear devices which have electrical characteristics similar to back-to- back Zener diodes. It is composed primarily of ZNO with small additions of other metal oxides such as Bismuth, Cobalt, Magnese and others. The Metal Oxide Varistor or "MOV" is sintered during the manufacturing operation into a ceramic semiconductor and results in a crystalline microstructure that allows MOVs to dissipate very high levels of transient energy across the entire bulk of the device. Therefore, MOVs are typically used for the suppression of lightning and other high energy transients found in industrial or AC line applications. Additionally, MOVs are used in DC circuits such as low voltage power supplies and automobile applications. Their manufacturing process permits many different form factors with the radial leaded disc being the most common.

The zinc oxide varistor body structure consists of a matrix of conductive ZNO grains separated by grain boundaries providing P–N junction semiconductor characteristics. These boundaries are responsible for blocking conduction at low voltages and are the source of the nonlinear electrical conduction at higher voltages.

An attractive property of the MOV is that the electrical characteristics are related to the bulk of the device. Each ZnO grain of the ceramic acts as if it has a semiconductor junction at the grain boundary.

Varistors are fabricated by forming and sintering Zinc Oxide-based powders into ceramic parts. These parts are then electroded with either thick film Silver or arc/flame sprayed metal.

The ZnO grain boundaries can be clearly observed. Since the nonlinear electrical behavior occurs at the boundary of each semiconducting ZnO grain, the varistor can be considered a "multi-junction" device composed of many series and parallel connections of grain boundaries. Device behavior may be analyzed with respect to the details of the ceramic microstructure. Mean grain size and grain size distribution play a major role in electrical behavior.

Product Information:

Type: varistor D42*H20mm

Material: Metal oxide varistor

Applicantion for Arrester Classification DH (IEC Standard)

Applicantion for Arrester Classification SL (IEC Standard)

Applicantion for Arrester Classification SM (IEC Standard)