Dielectric Withstand Test Levels

[nodee]

Hi,

I have a piece of equipment (with PCB) where the maximum voltage is 300V between adjacent traces.

What determines the dielectric strength test level for such a piece of equipment?

Regards
nodee

 

[D.A.(Tony)Stewart]

The strength and rated voltage are two different things.

If you are talking about only gaps , or creepage , the breakdown is typically 1-3 kV/mm for clean surface and much lower if contaminated with, dust, moisture, salts

 

[nodee]

Does the rated voltage lead to a specific test level?

 

[jiripolivka]

You do not indicate the distance between "adjacent traces" or substrate material, or air moisture under which your device should operate.

General rule is: avoid putting voltages >100V between "adjacent traces", use quality substrate and apply conformal coating on the board to avoid water condensation. Use quality PCB connectors and make sure the HV circuit is fused.

 

[nodee]

Im ok with all of that, im talking in terms of validation, what determines the test levels?

if your rated voltage is X the dielectric test level is Y

Thanks for your help

 

[jiripolivka]

I think mostly environmental conditions define test standards. I would use at least double voltage to test. Consider also possible occurrence of conductive dust which, combined with moisture, can and does damage mainly PCB connections

 

[FvM]

There's a number of standards specifying test voltages. I mostly refer to IEC1010.

For 300 V working voltage, basic insulation and overvoltage category I, the test voltage is 820 Vrms respectively 1150 V DC. Basic insulation and cat II (mains wiring) will be tested with 1350/1900V. For reinforced insulation and cat II (e.g. mains voltage against low voltage circuit), it's 2300/3250 V.

 

[nodee]

Thanks for the info,

I think the my confusion has come from dielectric strength vs impulse withstand voltage.

Is the impulse test also related to the rated voltage? is the impulse withstand voltage test part of the EMC requirements?

could someone clarify the difference?

Thanks!

 

[FvM]

Transient voltage strength (e.g. tested with 1.2/50 µs pulses) is an alternative measurement method in safety standard. It's also specified in IEC1010. The test voltage is 1500 V for cat I basic insulation, generally about factor 1.8 of the AC Vrms for 1 min rating.

 

[marce]

Have a look here and look for IEC 60950 stuff.....
http://www.creepage.com/

When the traces are on the outer layers of a PCB the dielectric is air and the spacing are for through air...
If you have high voltage you are better of putting the traces on inner layers then you can go down to around 0.25mm.