---- Steve Condie <

[email protected]> wrote:

My experience with this is that you can add the voltage if you wire a

multi-pole relays in series. Last year I wanted to switch a 1500 watt

heater powered off my 156 VDC (nominal) pack, and tried using 3 pole, 28 VDC

rated relays wired in series. Just one 3P relay didn't work - one of the

contacts arced and the relay melted down in a very satisfactory smoky mess.

Two 3P relays wired in series (6 contacts in all) did the trick.

Dave Cover wrote:

>

> I have a simple question about air gap and DC breakers. AC breakers don't

> need a lot of help

> extinguishing an arc because the voltage crosses zero many times a second.

> But DC voltage is

> constant and an arc might be sustained if the air gap is not large enough.

> And I assume that

> higher voltage needs a larger air gap. And for the purposes of this

> question, let's ignore

> magnetic blowouts, etc.

>

> Suppose we have a breaker with gap X and we needed to increase it's

> voltage rating. 2 of these

> breakers in series (mechanically tied so they trip together) would in

> theory give twice the air

> gap, or 2X. But neither air gap is larger than the original air gap X.

>

> My question is, does putting breakers in series increase the air gap (and

> voltage rating) by

> adding them together? Or is the voltage rating about the same as the

> original since the individual

> gaps are the same as the original? Don't forget, I'm asking so I can

> understand if putting

> breakers in series increases their voltage rating. Or not.

>

> Thanks

>

> Dave Cover

>

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