Metal oxide varistor(MOV) failure

Discussion in 'The Projects Forum' started by naveen123, Sep 16, 2013.

  1. naveen123

    Thread Starter New Member

    Sep 16, 2013
    3
    0
    Dear all,
    I am using an MOV for surge protection in one of our application. One of the MOVs connected between earth(gnd) and line fails frequently.The part number I have used is ZOV 07D431K. These are the ratings:

    1)Clamping voltage= 710V max
    2)Energy absorption= 28J
    3)Response time= 25ns max

    The varistor is rated at 275Vrms.
    I need help regarding this issue.
     
  2. Sensacell

    Well-Known Member

    Jun 19, 2012
    1,130
    266
    What is your nominal mains voltage? 110 / 220?
     
  3. Experimentonomen

    Member

    Feb 16, 2011
    331
    46
    You need a mov rated to the peak voltage which for 110v mains is 170v, and for 220v mains is 320v.
     
    naveen123 likes this.
  4. naveen123

    Thread Starter New Member

    Sep 16, 2013
    3
    0
    I am using a 230V ac supply. Shouldn't the rated voltage be 10% more than the ac supply rating i.e for 230 V does a 275 vrms sufficient? The MOV dia is 7mm
     
  5. MrChips

    Moderator

    Oct 2, 2009
    12,440
    3,361
    110% of 320V is 350V.
     
  6. RamaD

    Active Member

    Dec 4, 2009
    254
    33
    In India, mains voltage is not steady at 230V AC. Higher voltages are commonly seen near the distribution transformers, and also during night. 300V or 320V rms rated MOVs (not the peak voltage, which is higher) are generally used!
     
  7. Experimentonomen

    Member

    Feb 16, 2011
    331
    46
    Nominal peak voltage for 230V mains is 320V(this is what is seen after rectification and smoothing), for 240V mains the peak is more like 350V, so use 400Vrms or higher MOV's.
     
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