Varistor Voltage Help Please

[Frosty_47]

Hello,

There is probably a screwup with digikey, as it has three listing for Varistor Voltages:
a) Varistor Voltage
b) Maximum AC Volts (rms)
c) Maximum DC Volts

Parts (b) and (c) are clear to me. Part (a) confuses me, what do they mean by Varistor Voltage?


http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=Metal+Oxide+Varistor&stock=1


And Why the hell is Varistor Voltage always higher than AC and DC Voltage? Is this a digikey screw up or is there something I don't know about Varistors ?

 

[mneary]

You should not intentionally apply voltages above (b) and (c). They are the operating conditions, the voltage that can be applied forever with no conduction.

The Varistor voltage is the clamping condition, the voltage which, if applied, you can expect conduction. Voltages greater than (a) are supposed to be shunted.

The region between (b), (c), and (a) are not guaranteed to clamp but conduction may take place leading to failure.

 

[Frosty_47]

You should not intentionally apply voltages above (b) and (c). They are the operating conditions, the voltage that can be applied forever with no conduction.

The Varistor voltage is the clamping condition, the voltage which, if applied, you can expect conduction. Voltages greater than (a) are supposed to be shunted.

The region between (b), (c), and (a) are not guaranteed to clamp but conduction may take place leading to failure.

Thank you for your clear explanation