Reading label on a circuit breaker

justinjja

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Jul 11, 2020
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I'm looking at a 480v(ac) 3P 30A breaker,
dual rated for 250vdc 10ka

On the label it says this:

"Use Two 100% Protected Poles for DC"

Does that mean you can only use 2 of the 3 P for DC?
Or are you supposed to use 1P for + and 1P for - (Guessing no...)
... Or something else entirely?
 
Perhaps the manufacturer of the circuit breaker has a pdf on the 3 pole circuit breaker explaining how to use it for dc.


later floyd
 
EHD3030L is the breaker,
I didn't find anything in their PDF's for DC,

But I did find a picture of a new breaker which has a slightly different text:

"Use (2) 100% Protected Poles In SeriesFor DC"

Which makes (a little) more sense.
 
Yeah, I've seen some schematics and statements where you use "2" breakers in series for DC. I suppose 1 will start to trigger and the 2nd one finishes(?) I don't know the theory behind it.
 
I can think of 2 possibilities,
Maybe you just need the extra effective breaking speed and distance to meet the 250v rating.
Or maybe they have magnetic arc arestors, and you put 2 in series to cover you for both current directions.
 
I ran into a similar question for myself on two pole breakers.

I think they mean that you need to wire it like this. I'm not saying this is correct, but I made this for discussion purposes.


image_iekisf.jpg
 
@Crimp Daddy - What would be the logic of doing something like in the picture's left ?
 
Higher voltage tollerance. Larger gap basically.
 
Overmind said:
@Crimp Daddy - What would be the logic of doing something like in the picture's left ?

Generally speaking... and depending on the breaker, I have seen an increase in capability/rating when doing this.

Depending on the system voltage and requirements, it may be necessary to wire it in this manner.

As an example,here is the side of my ABB. Max voltage is different for 2 pole and 3 pole wiring.



image_zzayri.jpg
 
I have a under voltage shunt trip NOARK SHT3111UC 12-24V AC which controls a 4 pole EX9BP-N C 25A 1000V IEC/EN 60947-2 Ic=6KA THE cb are connected in series as shown in the photo

image_wjmqyv.jpg

The shunt trip was in the LG RESU HV system I picked up a couple weeks ago. 25A doesn't seem a lot till you figure it at the voltages the unit ran at 350-550v. This was in the dc-dc converter. I hadn't seen a Cb connected like this before.

Later floyd
 
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