IEC 61010 Creepage and Clearence Requirements

[Freddybaby]

We have a sub-assembly we supply that has a push button on the front panel that the users second party safety assessor is requiring UL listing (or other) to the internal working voltage of 40KVDC.

This switch is in the 24V control system but is in the vicinity of a "simple voltage divider" and if breakdown of the resistor string occurs at the time someone pushes the button it's a shock hazard.

There are NO conductive parts including the switch plunger that extend beyond the protective earth guard (the front panel) but the creepage from switch terminals to the users finger is not adequate for the working voltage.

Hi-pot testing has proven that all HV arcs are diverted to the front panel.

My question is: Can we use a suitable (UL listed type 5) voltage clamp on each side of switch to the earthed panel to get around the creepage needed for the full voltage.

In other words, the voltage should never rise to 40KVDC as the clamp will divert and all conductive parts of the switch assembly are behind the earthed panel.

 

[Stijloor]

A Quick Bump!

Can someone help?

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Thank you very much!

 

[Hershal]

I have assessed IEC 61010-1 and several -2s many times. Generally the applicable -2 and parent paragraph in the -1 is pretty clear. However, your question is specific. I would work with your customer, lay out the design and circuitry, and let the UL Engineers do their thing. I know UL well, and many of their Engineers. Trust their call, and abide by it. But give them what they need to make the call.

Hope this helps.