Varistor Requirements?

Discussion in 'General Electronics Chat' started by bogey912, Oct 16, 2016.

  1. bogey912

    Thread Starter New Member

    Oct 16, 2016
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    Hi folks, great board here. I have a couple of varistors that blew. The one next to the blown ones says S14 , K130 , 0009. During some googling, I found that the 14 is the diameter of the varistor in mm and the 130 is its voltage rating. I have found some varistors on Ebay that say 14mm 680volts. My first question is it alright to use a varistors with a higher rating than the old one. I'm assuming the diameter is not as critical (if it fits) as the voltage rating?
    Also what is the best way to test a varistor? Can I do it in circuit? I have a 500vdc megger. would that help? Thank You for your time!
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Welcome to AAC!
    Generally, no. The purpose of the varistor is to protect the circuit from excessively high voltage.
    Diameter is important. Bigger varistors are usually able to absorb more energy.
     
  3. bogey912

    Thread Starter New Member

    Oct 16, 2016
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    Thanks for the info!
     
  4. bogey912

    Thread Starter New Member

    Oct 16, 2016
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    Opps, I forgot the second part of my question.
    "Also what is the best way to test a varistor? Can I do it in circuit?" Can you tell me this? Thanks!
     
  5. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
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    It basically looks like a back to back Zener diode with high short term surge capability. Usually, they visibly self-destruct. A curve-tracer or I-V curve would be a basic test.
     
  6. dl324

    Distinguished Member

    Mar 30, 2015
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    Testing a varistor in circuit puts the components it's supposed to protect at risk.
     
  7. bogey912

    Thread Starter New Member

    Oct 16, 2016
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    So from your guy's comments, their is no "easy" way to test a varistor (like with a dmm). If they are not blown, its safe to assume they are ok I guess. Thanks again.
     
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