Reading label on a circuit breaker

Announcement - Help us fight the BOTS! Please report all spam including stuff in your inbox!

justinjja

New member
Joined
Jul 11, 2020
Messages
8
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?
 

floydR

Member
Joined
Aug 23, 2017
Messages
1,314
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
 

justinjja

New member
Joined
Jul 11, 2020
Messages
8
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.
 

Korishan

Moderator
Joined
Jan 7, 2017
Messages
6,552
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.
 

justinjja

New member
Joined
Jul 11, 2020
Messages
8
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.
 

Crimp Daddy

Member
Joined
Feb 21, 2018
Messages
962
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
 

Overmind

Member
Joined
Jan 16, 2019
Messages
450
@Crimp Daddy - What would be the logic of doing something like in the picture's left ?
 

daromer

Moderator
Joined
Oct 8, 2016
Messages
5,659
Higher voltage tollerance. Larger gap basically.
 

Crimp Daddy

Member
Joined
Feb 21, 2018
Messages
962
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
 

floydR

Member
Joined
Aug 23, 2017
Messages
1,314
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
 
Top