Shunt trip voltage

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LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
You should also know that most shunt-trip breakers are not designed to have the trip coil constantly energized. This is usually accomplished by having the coil fed from the circuit that the breaker itself supplies.

The wording on the label of this breaker is saying that the tripping coil is disconnected when the breaker is off or tripped.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
You should also know that most shunt-trip breakers are not designed to have the trip coil constantly energized. This is usually accomplished by having the coil fed from the circuit that the breaker itself supplies.

The wording on the label of this breaker is saying that the tripping coil is disconnected when the breaker is off or tripped.

Honestly, I would have missed that :lol::eek::slaphead:
 

Tony S

Senior Member
You should also know that most shunt-trip breakers are not designed to have the trip coil constantly energized. This is usually accomplished by having the coil fed from the circuit that the breaker itself supplies.

The wording on the label of this breaker is saying that the tripping coil is disconnected when the breaker is off or tripped.

Supposed to be disconnected when the breaker has opened. Doing maintenance and testing on a 433V switchboard. In one afternoon I had two 1600A ACB shunt trips fail because the disconnect micro switches were out of alignment. Smoke was coming out of breaker one so I swapped the feeder over to breaker two, magic blue smoke again.

The smell of burnt insulation lingered in the switchroom for days.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Supposed to be disconnected when the breaker has opened.
I agree, which is why I mentioned it, and it never hurts to do it that way. Several years ago, I had to replace a large 3p breaker in a restaurant kitchen for a fire-marshal inspection, because a manual push-button that had a push-and-turn latch position had been installed, and burned out the coil. I re-wired it so the shunt circuit was powered from that breaker.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
You're confusing me. Applying voltage to the shunt-trip coil causes the breaker to trip. That voltage needs to be momentary because you can burn up the shunt-trip coil. So whatever scheme you use to trip the breaker, the voltage cannot be sustained after the breaker trips hence the recommendation to use the breaker itself to supply the control voltage. But sometimes that's not possible with higher voltages.

I believe the wording on the label indicates that there are internal interlock contacts that disconnect the shunt-trip coil when the breaker trips or is in the off position. It's not an advisory to remove voltage when the breaker is tripped or off. So if you have to supply the shunt-trip coil with a constant voltage after the trip you are good to go, at least with that breaker.

Don't know if that's what you meant or not. Just trying to clear up any confusion.

-Hal
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Your understanding is correct. Apologies for the confusion.

It's a generalization that trip current be momentary. This breaker states that it's not a concern in this case, and you have the option. It's never necessary that the current be continuous.
 
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