Resistor Maximum Working Voltage

[jpalicke]

I had a question about the maximum working voltage rating on resistors.  Is it defined as the maximum voltage across the resistor, or the maximum voltage with respect to ground?  Seems like it should be the former, but I've seen people say it's the latter.  Which is it?

Joe

[JoeN]

[free_electron]

Volage across the resistor.

[jpalicke]

Many thanks!

Joe

[T3sl4co1l]

^

[SeanB]

For power resistors there are also ratings for the voltage between the resistor leads ( any of them) and the case if it is a metal case for cooling, and if there is a water cooling connection. Ceramic resistors also have a rating for hot and cold use, as when they are at full power dissipation they are no longer usable as insulated case resistors, the case must be considered as conductive as the ceramic can carry current if it is red hot. You often get them with a steel mounting, which must be connected to one lead in operation, or soldered to the board and isolated.

[TimFox]

For a given series of resistors, (e.g., 1-watt carbon) especially ones designed for high voltage, there is a resistance value often specified for that series where the resistors are limited by voltage (lead to lead) above that resistance, and by power rating below that resistance.

[katzohki]

Usually most people are concerned with the power rating of the resistor, but voltage is a good thing to keep in mind. Since I work with high voltages in my circuits (up to 10kV) I have to get special resistors that are high voltage rated.

[cosmicray]

Datasheets for resistors will commonly show a maximum DC Working Voltage, and a maximum DC Overload Voltage. A couple of datasheets I looked at, showed an overload voltage that was 2x the working voltage (for axial resistors).

[Zero999]

It's not just blowing the resistor up which you risk by exceeding the voltage rating: at higher voltage the resistance often drops below the rated value.

[Neilm]

Datasheets for resistors will commonly show a maximum DC Working Voltage, and a maximum DC Overload Voltage. A couple of datasheets I looked at, showed an overload voltage that was 2x the working voltage (for axial resistors).

I have seen short term overloads of 5 or 10 times the rated voltage, depending on the resistor construction and the length of  time of the overload.