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Metal Oxide Varistor

The Metal Oxide Varistor or MOV is a voltage dependent, nonlinear device that provides excellent transient voltage suppression. The Metal Oxide Varistor is designed to protect various types of electronic devices and semiconductor elements from switching and induced lightning surges.

When exposed to high transient voltage, the MOV clamps voltage to a safe level. A metal oxide varistor absorbs potentially destructive energy and dissipates it as heat, thus protecting vulnerable circuit components and preventing system damage. Varistors can absorb part of a surge.

About the MOV – Metal Oxide Varistors

A MOV contains a ceramic mass of zinc oxide grains, in a matrix of other metal oxides (such as small amounts of bismuth, cobalt, manganese) sandwiched between two metal plates (the electrodes).

 

Related Products: Circuit Protection Misc | Transient Blocking Units | Varistor | TVS | Surge Suppressors

 

They can be connected in parallel for increased energy-handling capabilities.
MOVs can also be connected in series to provide higher voltage ratings or to provide voltage rating between the standard increments.

A Metal Oxide Varistor remains non-conductive as a shunt mode device during normal operation when voltage remains well below its “clamping voltage”. If a transient pulse (often measured in joules) is too high, the device may melt, burn, vaporize, or otherwise be damaged or destroyed.

The varistors must on all accounts be connected parallel to the electronic circuits to be protected.
mov connection

As Sivanand said on one article: “A Metal oxide varistor SHOULD be used to protect the circuit from HV spikes… It has become mandatory and can be seen in all power supplies that works off directly from mains.”

metal oxide varistors

31 Comments

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  • Dahiru

    Will someone kindly suggests a car phone charging circuit. I actually want to design a kind of family phone charging power park.
    So I need a circuit that charges the lead acid battery and the phone charger if the battery is 6v.
    Can I also use LM317 for the phone charger?
    Thank you.

  • mwy

    dear sir,

    can u please explain to me bout the operations of mov in details?

  • Rajshri Satputaley

    Sir i required MOV to protect IGBT in the inverter circuitary from spikes My d.c. link voltage is maximum 100 Volt or 200 Volt can us uugest me thow to select mov and which brand

  • Sal

    Hello everyone

    I have a coffee maker 127V – 550 Watt with auto shutoff (circuit board) and has an MOV in that board.

    If I install a 5Amp fuse then an MOV between the mains and the board, will the MOV that I installed clamp in the case of a voltage spike (230V) and the MOV in the board will not clamp or will both of them clamp?

    Note: I’m trying to make protection from a 230V.

  • Suvendu Samanta

    Dear Sir,

    During my experiment I was using MOV-20D471K varistor (517V max) to protect a 650V mosfet.. In other circuit I need to protect a 1200V SiC MOSFET.. Can I use 2 varistors in series?

    • Suvendu Samanta

      Thank you Sir…

    • Jim Keith

      Series operation of metal oxide varistors increases the clamp voltage rating as well as the energy rating –recommended.

      However, parallel operation is poor because one device tends to ‘hog’ the current and is thus subject to premature failure.

  • Ishwar

    Dear sir
    In electronic ballast of T-5 tubetube light, when there any fault in supply like double phase (440) or hi voltage then transistor and some resistor burnt. How should I protect it. Standard voltage is 240 volt 0.28 Amp. 50 Hz.

    • pradhyuman

      sir mov having the polarity or not ?

    • Ishwar

      Dear sir
      In electronic ballast of T-5 tubetube light, when there any fault in supply like double phase (440) or hi voltage then transistor and some resistor burnt. How should I protect it. Standard voltage is 240 volt 0.28 Amp. 50 Hz.

  • Ramesh S

    S14 K130 is a EPCOS make varistor. Refering to the datasheet, it is found that S14 stands for 14mm dia varistor & 130 is towards maximum operating volatge (130V ac & 170V DC). It can handle 34J of power. Any varistor which can meet this specification can be used. If you dont get a 14mm dia part, goahead with 20mm diameter part. Ofcource cost will be little high and also, need to consider the available mounting space.

  • Mahtab

    The lebel of a varistor is S14 K130 0130 (blue in color) which is burnt and open ckt. Which varistor I should buy to replace it or what does mean the lebel of varistor above?

    Thanks a lot. Please help.

    • Mahtab

      Thanks a lot Mr. Jim Keith. Can you suggest me to find out the voltage rating of a MOV from code (or lebel) written its body?

    • Jim Keith

      This is a 130VAC varistor (MOV) with a 14mm diameter.
      Suggested replacement:
      Bourns MOV-14D201K
      DigiKey MOV-14D201K-ND, $0.20each

      There are many 130VAC devices that will work –generally non-critical.

  • Ramesh S

    Many circuits are already there in the web. You can download & use them. Since you have mentioned that, you need a simple one, herewith find the link for one such simple circuit.
    http://www.eleccircuit.com/solar-battery-charger-with-overcharge-protection/

  • anandam boora

    simple circuit is required by adding component across solar panel.

    • todosnivelesgmail-com
      Your comment is awaiting moderation.

      Hi,

      I’m curious about Jim Keith’s comment regarding series operation.
      In this schematic we see two placements of a varistor for surge absorption protection of a solid state relay.

      https://www.ia.omron.com/support/faq/answer/18/faq02075/

      If one places a varistor in series is there any need to place a second one in parallel

      Any thoughts.

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