High Voltage DC Circuit Breakers

Desert Rat

Midnite has this 300V breaker with a jumper on the bottom two terminals, so it is intended for the positive conductor to be wired to the top two terminals.

This breaker has an accompanying diagram showing both positive and negative conductors passing through the breaker.

Is there any reason not to install a jumper on the bottom two terminals and wire the same way as the Midnite breaker? Or is that even necessary for 300V since this breaker is rated for 500V?

BB.

Not withstanding using the breakers in series to up the village rating is probably not in the manual and not CE/NRTL listed...

1. If breaker is rated or 500 volts(DC or AC?) and you are using 300 volt circuit, then should not be series connected.

2. If DC rated breaker, is breaker polarized (+ & - terminals)? Polarized breakers should never be reverse connected as even manual trip below rated current, will draw the arc into the breakers internals (as opposed into the arc quenching section) and ruin the breaker and easily catch it on fire.

3. If the breaker body is rated for 500 volts, unknown if body is rated for 1,000 volts. Note that AC components are factory tested for 3x rated voltage final test (hipot)--So there is a safety margin...

4. Appears the the two handles are interconnected. Required for a two pole breaker normally and would be required for series breakers too.

The Midnite series breakers are, at least, tested and rated for application.. and the manufacturer has proprietary information you do not. I have asked UL for this information before and would not supply to me even though needed for Listing of our equipment. What the mfg may choose to make public in specifications is not enough for you to make your own design 'updated'.

Issues that I can think of...

-Bill

NANOcontrol

If the breakers are ganged, you might as well put them in series. Especially ones from China for some redundancy.  I've tested a lot of them for arcing and putting them in series doesn't change them much. Even ones with marked polarity didn't have that much change when reversed.  Some actually worked better reversed.  Surprising how low the voltage has to go before the arc extinguishes. I thought I had a trace to show I actually do test them. I had moved them to a storage drive. Post some later.

BB.

More or less, I believe that DC Voltages at 12.xx volts and above can "start/sustain" themselves (from a quick internet search a few years ago--Darn, it is difficult to find that paper/website now). More or less, 14 volts is the present "agreed" minimum "arc" voltage from many sources.

Be very careful about reverse current flow in DC polarized breakers... Depending on brand/design/etc.--There are breakers that will easily sustain and arc/catch fire even when manually operated (reverse current) at (as I recall) less than 10 amps.

A quick thread with some nice Video examples of reverse current flow arcing (yea--I know, Youtube):

https://forum.solar-electric.com/discussion/comment/426128

-Bill

NANOcontrol

Just about any contact will work up to 30V.  Silver contacts are the worst.  Here is a breaker test of a DC only breaker with magnet suppression in reverse.  Arc is about 100 microseconds longer.  Arc stops at about 35V.  Supply is about 90V.