In looking at an installation with remote DC [batteries] I noticed the battery breakers provided have two poles wired in series from the factory [for example load side of phase “a” is pre-wired to the line side of phase “b”] From what I can find this has to do with DC having no natural zero crossing to extinguish the arc. In doing some research I could not find exactly what I was looking for, for those experienced in this could anyone provide any links to additional technical articles or texts / books that would provide additional information [thanks]. Also how is it determined when multiple poles are required to be wired in series is this related directly to the system current, voltage or both?? I have seen some documentation that shows no poles in series some, where two or even three are wired in series.
D.C. Breakers
- Thread starter Mike01
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- Placerville, CA, USA
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- Retired PV System Designer
It is common when using breakers rated separately for DC and AC to specify the use of two or three poles in series to get the needed voltage capability when handling DC. If does have to do with the separation of the contacts in the open position versus the length of arc gap needed to extinguish an arc when opening under load.
I have seen it used for higher voltage PV strings, but not for typical battery voltages.
Is this for a UPS with 120V or higher battery circuits?
I have seen it used for higher voltage PV strings, but not for typical battery voltages.
Is this for a UPS with 120V or higher battery circuits?
petersonra
Senior Member
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- Northern illinois
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- engineer
you often see this with contactors as well.
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- Placerville, CA, USA
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- Retired PV System Designer
And this usually makes the breaker polarity sensitive, able to interrpt full load current only when it is flowing in the correct direction through the breaker.
Tony S
Senior Member
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- Resting under the Major Oak UK
I’m surprised a manufacturer is using breakers in this way when duel rated breakers are available.
The blow out coil draws the arc around the arcing horn rapidly widening the arc path and drawing it in to the splitter plates.
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- Placerville, CA, USA
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- Retired PV System Designer
Small DC breakers will often use a permanent magnet instead of a blowout coil.
If you need to have fuses they also must be DC rated. I've seen a few nasty messes when they weren't, one of them of my own doing.....................
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