DC breaker

[QSIMDO]

12 volt, 30 amp breaker has "BATT" on one pole an "AUX" on the other.
Power will be coming from regulator/rectifier and the other to the battery.
One would assume that "BATT" would be going to the battery but does it really make a difference?

[MaxHeadRoom]

Some breakers have AUX switched contacts mainly for indication or monitoring etc, may not be as heavy a contact as the BATT side.
Max.

[Paul Alciatore]

Yes, DC breakers are most frequently used inside of equipment so monitoring circuits can be desired. The breaker trips and a warning light comes on or some other action is taken.

I have seen many DC breakers and all of them were built into a piece of equipment of one sort or another. Once or twice they were in a DC distribution panel. Places with a lot of electronics, like TV stations, often had one large DC power supply and then it was distributed to multiple places, often through breakers to isolate problems.

"Batt" most likely refers to the source of the DC current and that would most likely be a DC power supply. Only in some instances would that be an actual battery. This labeling probably comes from a design engineer with a lot of experience with battery powered systems. I would assume that the "Batt" pole would be the main current path.

If you want to see the exact specs. on the breaker you have, you can probably look it up on one of the electronic parts web sites. They provide links to the data sheets of most of the parts they sell and links to the web sites of all the manufacturers. A data sheet is probably only a few clicks away.

https://www.digikey.com/

https://www.mouser.com/?utm_source=bing&utm_medium=cpc&utm_campaign=Local%20Campaign%20(Texas)&utm_term=mouser&utm_content=Brand%20Mouser

https://www.newark.com/

And more. The electronic industry has tremendously better support on the web as compared to machining/tools or materials or mechanical components. And it is so much easier to use. I can have a complete OEM data sheet on almost any electronic component in less than a minute. You could spend hours trying to find something like that on a mechanical component.

[Noitoen]

Some DC breakers have a magnet to "blow" the contact spark and this helps if the polarity is correct in relation to the magnetic field.

[Cuttings]

Here is a link to a video of what happens to a polarized DC circuit breaker if it is wired incorrectly and turned off under load
<https://www.youtube.com/watch?v=Oaq2cvoPBRk>

[chipmaker4130]

You mean like this one? Its from an old Marquette brand battery charger. The posts are marked Bat and Aux, the Bat goes to the source, in this case the rectifier output of the charger. The Aux feeds the load which is the battery being charged. So Bat in this case really isn't!

[dian]

Some DC breakers have a magnet to "blow" the contact spark and this helps if the polarity is correct in relation to the magnetic field.

how does that work?

[QSIMDO]

You mean like this one? Its from an old Marquette brand battery charger. The posts are marked Bat and Aux, the Bat goes to the source, in this case the rectifier output of the charger. The Aux feeds the load which is the battery being charged. So Bat in this case really isn't!

Sorted!
Thank you all!

[Peter.]

how does that work?

The blow out coil creates a magnetic field that pushes the arc in a loop away from the contactors until the loop becomes too long to maintain itself and the arc extinguishes. Without it the blowout coil the arc will live long enough to cook the contacts.

[MaxHeadRoom]

Some DC breakers have a magnet to "blow" the contact spark and this helps if the polarity is correct in relation to the magnetic field.

Also DC relays of a heavier current type, I have used these such as P&B where high DC current is switched, avoids the plasma arc (welding) of contacts.
Max.

[PStechPaul]

I'm surprised that the polarized DC breaker in the video destructed so catastrophically. I could understand that happening with an inductive load, but this was just a loop of wire, and only 10 amps. I wonder if the source he used had inductance, or possibly was a current regulated circuit backed up with a high voltage. Apparently those breakers were common in Australia until around 2010 when the problem was identified and an effort was made to correct the installations and install safer protectors.

[Noitoen]

I'm surprised that the polarized DC breaker in the video destructed so catastrophically. I could understand that happening with an inductive load, but this was just a loop of wire, and only 10 amps. I wonder if the source he used had inductance, or possibly was a current regulated circuit backed up with a high voltage. Apparently those breakers were common in Australia until around 2010 when the problem was identified and an effort was made to correct the installations and install safer protectors.

For the video's sake, I would think that he dipped the breaker in some flammable liquid. In that way he got the show on the first take(or not). The breaker will fail but not like that. After repeated arcing you might char the inside and then a catastrophic failure. Just a few months ago, I decommissioned some ABB control gear with many of those polarized ABB breakers. Next week I will be back to work after a 2 week quarantine (and if my covid19 test from this afternoon comes negative) and I will break one open to see if they use a coil or a magnet

[darryl]

Looks like a joke to me- that's fuel burning, not the contents of the breaker. If that's the contents of the breaker, then it could never have passed a certification. Of course, it could be a piece of crap from China that 'cheated' its way into the industry, like so many other products appear to have done.

I'm not saying that polarity should be ignored- but that looks just like gasoline burning.

If it's not faked, then the parts being shown should never be allowed in any system. I bet it's expensive shist too

[dian]

where does the arcing energy come from here?

https://www.youtube.com/watch?v=Zez2r1RPpWY

[Paul Alciatore]

The energy is coming from the DC power source. When the switch first breaks contact, a small arc starts between the contacts. That arc ionizes the atoms of the various gases in the air and those ions, along with their liberated electrons form the conductive path. Then, as the gap between the contacts increases, more ions and electrons are created and the size of the arc grows.

This does not happen with AC because the AC Voltage goes to zero two times each cycle and then the polarity reverses. This provides some time, a very short time, but some time for those ions to cool off and recombine with the free electrons. This is further enhanced by the reversal of polarity which turns them around in mid air so they race back towards each other. The AC power source probably has just as much energy as the DC one, but it also has this feature of AC current that allows the arc to die.