Metal oxide varistor(MOV) failure

Thread Starter

naveen123

Joined Sep 16, 2013
3
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.
 

Thread Starter

naveen123

Joined Sep 16, 2013
3
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
 

RamaD

Joined Dec 4, 2009
328
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!
 
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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