Metal oxide varistors (MOVs, also called as Zinc oxide elements or ZnO blocks)

Technical information

Metal oxide varistors (MOVs, also called as Zinc oxide elements or ZnO blocks)

Metal oxide varistors (MOVs, also called as Zinc oxide elements or ZnO blocks)

Metal oxide varistor (MOVs, also called as Zinc oxide elements) , the heart of OTOWA’s SPDs and surge arresters, are manufactured under strict quality control. When an overvoltage such as a lightning surge is applied, it instantly changes from high impedance to low impedance. By becoming low impedance, overcurrents such as lightning currents can flow to the secondary side (grounding side, etc.), after which it automatically returns to high impedance immediately.

A complex structure of micro varistors consisting of Zinc oxide grains and surrounding high-resistance grain boundary layers, connected in series and parallel. Therefore, if the size of the Zinc oxide grains is the same, the varistor voltage is proportional to the thickness and the surge withstand capability is proportional to the cross-section area of the MOV. (Photo taken by our scanning electron microscope)

Microgram of MOV surface

Image of microstructure

Fig. Microstructure of ZnO varistor elements.

Electrical characteristics
Compared to ordinary resistive elements, MOVs have a very large non-linear voltage-current characteristic, so they act as insulators in areas where the applied voltage is small, and as conductors in areas where the voltage is large, such as in lightning surges. This makes it possible to safely protect equipment from lightning surges.

Fig. Ideal V-I characteristics of MOV

Features of Metal oxide varistor (MOV)

The MOVs used in surge arresters and surge protective devices (SPD) are manufactured under strict quality control and have excellent non-ohmic properties, high surge withstand capability and longer service life.

Excellent non-ohmic property
When an excessive surge is applied to a MOV, the terminal voltage of the MOV is kept as low as possible to protect electronic equipment and power facilities.
High surge withstand capability
Uniformly current flow in an MOV due to high homogeneity of daily improved ZnO ceramics and high collaring materials having high insulation are realized.
Long service life
High reliability under the condition that system voltage is constantly applied.
Wide range of products
A wide range of AC and DC products, from low to high voltage, are available to meet a wide range of needs. Our MOVs satisfy international standards related to surge arresters, SPDs and MOVs(IEC, IEEE,UL etc..)