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How to choose metal oxide varistors?


MOV model selected:
Many of our customers don't know how to select Metal Oxide Varistor model.
Hereby, we suggest varistor voltage selected should be 2.2~2.3 times of supply voltage.
USA for example, supply voltage in USA is 120V,just equal to 120Vx2.2~2.3=264V~276V.
So we suggest customers from USA should choose MOV= DXM-xx/D/271/K for your circuit.

Our PTC&MOV composition product for good lightning surge protection
One PTC&MOV composition product with 2 or 3 leads made by us has good performance of lightning surge protection.
Dimension and outlook of it is as below:

It can provide extra protection of the ballasts and led products. USA for example, the device will hold at a detailed current with a supply voltage of 120 vac and at 130 vac will cause the MOV UNITS to conduct and cause a high ampere and in turn the PTC thermistor UNITS will sense a high current and open the supply voltage protecting the ballast or led unit and reset after cool down period has occurred. This to be the most efficient way of providing surge protection and results in very long life for ballasts and led products. It can also be used for outdoor led lights to make sure that they also survive electrical storms as well.   

These metallic oxides have semiconducting characteristics, because it has the same or similar electric conduction mode with the semiconducting material such as Ge, Si. When in low temperature, current carrier of oxide material (electronic and cavity) is in less number, it’s in high resistance; with the increase of temperature, quantity of current carrier increases, so resistance decreases accordingly. NTC thermistor can be widely used in surge current limiting, temperature measurement and control, temperature compensation etc. The resistance change range of NTC thermistor in room temperature is 10O~106Ω, temperature coefficient is -2%~-6.5%.