I've never seen the internal make up of a breaker but would'nt it have to have some sort of resistor inside of it to limit the flow of current in a circuit. for example a 20 amp breaker would have to have something to limit more than 20 amps from coming thru it. without some sort of current limiting device any amount of amps could flow thru. and is this not why breakers sometimes go bad because over time that resistive element finally burns out and this is why we change bad breakers.
breakers
- Thread starter elect36
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- Illinois
- Occupation
- retired electrician
Re: breakers
In general breakers do not limit the flow of current. They react to the excessive flow of current and open their contacts to stop the flow of current.
Don
In general breakers do not limit the flow of current. They react to the excessive flow of current and open their contacts to stop the flow of current.
Don
Re: breakers
e36
Check out this location http://www.eatonelectrical.com/unsecure/html/101basics/Module05/Output/index.html
and maybe take an old breaker apart ans see what is inside.
e36
Check out this location http://www.eatonelectrical.com/unsecure/html/101basics/Module05/Output/index.html
and maybe take an old breaker apart ans see what is inside.
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
Re: breakers
elect36,
While the current that flows when a short circuit occurs is large, it is not "any amount", or as I take you to mean, unrestrained or infinite.
The power company transformer secondary supplying the current has a resistance. It is small, but it is an important resistance. The service entrance and service drop/lateral conductors have a small resistance also. And the branch circuit conductors have a small resistance. The arc at the short (if there is an arc) also has a resistance.
All these little resistances add together to be the limit. A real world short is not often a very low resistance bolted short. So, the conditions of the actual short also help to reduce the peak current.
The contacts in the circuit breaker are designed to open and extinguish the arc created by interrupting the large current that flows during a short circuit. The common breaker today is rated 10,000 amps interrupting capacity.
A 20 amp 125 volt circuit in a single family dwelling will generally have a available short circuit of a few hundred to a few thousand amps. That allows the breaker to extinguish the arc when it opens.
If the arc can't be extinguished, the arc continues and burns things up.
elect36,
While the current that flows when a short circuit occurs is large, it is not "any amount", or as I take you to mean, unrestrained or infinite.
The power company transformer secondary supplying the current has a resistance. It is small, but it is an important resistance. The service entrance and service drop/lateral conductors have a small resistance also. And the branch circuit conductors have a small resistance. The arc at the short (if there is an arc) also has a resistance.
All these little resistances add together to be the limit. A real world short is not often a very low resistance bolted short. So, the conditions of the actual short also help to reduce the peak current.
The contacts in the circuit breaker are designed to open and extinguish the arc created by interrupting the large current that flows during a short circuit. The common breaker today is rated 10,000 amps interrupting capacity.
A 20 amp 125 volt circuit in a single family dwelling will generally have a available short circuit of a few hundred to a few thousand amps. That allows the breaker to extinguish the arc when it opens.
If the arc can't be extinguished, the arc continues and burns things up.
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