Varistor Derating Guidelines

How to Derate Voltage-Sensitive Resistors [metal Oxide Varistors]

Thermistor Derating
Varistor Power-Derating Curve

This style of Varistor is rated to operated out to at +85oC before any derating is required. However above 85C the power must be reduced as the varistor temperature increases. A derating chart is often used, with derating starting at 25oC. Since parameters are application dependent, power de-rating curves or charts should be considered general rather than absolute, and only used as a guideline. The safest designs use the largest physical size operating at conservative temperatures and power ratings. The minimum power dissipation for this style varistor occurs at 125 degrees centigrade.

MIL Spec Varistor Style RVS10 mil-prf-83530
Varistor Dimensions / Varistor Component Outline

Power rating. The average power dissipation rating applicable to parts covered by this specification is1.0 W at 85OC. For varistors operated at ambient temperatures in excess of 85C, the voltage shall be derated in accordance to the derating curve shown above.


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Reliability, Over-voltage
Rated Temperature

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Modified 6/13/15
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