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I understand withstand voltage test is to check the insulation of a product, for example between a live metal part (AC input terminal block) and a dead metal part.

I saw this specification in one of our products. It says withstand voltage between same polarity of output relay is 1000 Vac.

The product has two relays. Let's name the output of relay 1 as COM1 and NO1 and output of relay 2 as COM2 and NO2. All relay contacts are connected to an output terminal block (exposed metals) via PCB routes. Where is this 1000 V applied and what does "between same polarity mean"?

Does it mean between NO1 and NO2 or COM1 and COM2? It doesn't make sense to me though because the contacts of relay 1 is completely isolated to relay 2 output contacts in the first place.

Unfortunately, I couldn't use "withstand" in the tags. Sorry about that.

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  • \$\begingroup\$ I can try to answer the first part of your question: (1) COM1 and NO1 can withstand a voltage of 1,000V between the two contacts. As you said, the connection/wiring are via PCB routes/copper traces. (2) If the traces are routed/places too close together, a very high voltage might break down the insulation, say fiber glass, between the COM1 and NO1 traces. (3) A usual manufacturer trick is to cut the insulation part between the two contracts (actually three contacts), as shown in the figure below. \$\endgroup\$
    – tlfong01
    Oct 20, 2021 at 8:22

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I can try to answer the first part of your question:

(1) COM1 and NO1 can withstand a voltage of 1,000V between the two contacts. As you said, the connection/wiring are via PCB routes/copper traces.

(2) If the traces are routed/placed too close together, a very high voltage, say 1,000V, might break down the insulation, perhaps fiber glass, between the COM1 and NO1 traces.

(3) A usual manufacturer trick is to cut the insulation part between the two contracts (actually three contacts: COM1, NO1, and NC1), forming a U shaped "grove" as shown in the photo below.


rlay contact


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