Circuit Breaker Definitions - Article 100


Circuit Breaker: see fig.1

A device designed to open and close a circuit by non-automatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within its rating.

 

fig (1) : different types of circuit breakers

FPN: The automatic opening means can be integral, direct acting with the circuit breaker, or remote from the circuit breaker.

Or
A switching device capable of making, carrying, and interrupting currents under normal circuit conditions, and also of making, carrying for a specified time, and interrupting currents under specified abnormal circuit conditions, such as those of short circuit.

Adjustable (as applied to circuit breakers):  see fig.2 & 3

A qualifying term indicating that the circuit breaker can be set to trip at various values of current, time, or both, within a predetermined range. 





fig (2): Adjustable settings of Adjustable circuit breaker

Nonadjustable (as applied to circuit breakers):  see fig.3


A qualifying term indicating that the circuit breaker does not have any adjustment to alter the value of current at which it will trip or the time required for its operation. 


 
fig (3)


Interchangeable (as applied to circuit breakers):  see fig.3 

The user cannot change the trip unit in many circuit breakers, but some circuit breakers have an interchangeable trip unit, this feature allows the user to change the continuous current rating of the breaker without replacing the breaker, this is done by replacing the trip unit with one of a different rating. 




Instantaneous Trip (as applied to circuit breakers):  see fig.4

A qualifying term indicating that no delay is purposely introduced in the tripping action of the circuit breaker.


 

fig (4): please, study the curves ,and try to know the difference
 between Instantaneous and inverse time, and write it in the comments. 



Inverse Time (as applied to circuit breakers): 
see fig.4 

A qualifying term indicating that there is purposely introduced a delay in the tripping action of the circuit breaker, which delay decreases as the magnitude of the current increases.


Setting (of circuit breakers): 
see fig.2

The value of current, time, or both, at which an adjustable circuit breaker is set to trip.



Device: 
see fig.5 & 6

A unit of an electrical system that is intended to carry but not utilize electric energy. 


 
fig (5): Devices but not act as disconnecting means


Components (such as switches, circuit breakers, fuseholders, receptacles, attachment plugs, and lampholders) that distribute or control but do not consume electricity are considered devices.



Disconnecting Means:
A device, or group of devices, or other means by which the conductors of a circuit can be disconnected from their source of supply.



fig (5): Devices and act as disconnecting means

In the next topic , new definitions from NEC Code Article 100 will be highlighted.


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