LOW VOLTAGE CIRCUIT BREAKERS BASIC SELECTION CRITERIA

CRITERIA ON THE SELECTION OF LOW VOLTAGE CIRCUIT BREAKERS

Basic Circuit Breaker Selection Criteria

Low Voltage Circuit Breakers

The selection of any circuit breaker, for any given duty, is ultimately based on an assessment of its ability to perform the following basic functions:

a) To carry the required full-load current without overheating (i.e., it should have the correct current rating)

b) To switch and isolate or disconnect the load from the source at the given system voltage (i.e., it should have the correct voltage rating),

c) To interrupt any possible abnormally high operating current or short-circuit current likely to be encountered during operation (i.e., it should have the correct interrupting rating)

d) To be able to perform these functions over an acceptably long period of time under the operating and environmental conditions that will actually prevail in the application (i.e., it should have the correct mounting provisions, enclosure, and accessories for operation in the environment in which it is to be applied).

The degree to which a circuit breaker can satisfy these requirements is a measure of its applicability

for a function. A circuit breaker's rating indicates these capabilities to the user because rating is established by proof testing.

Hence, an understanding of how a circuit breaker of any given type is tested will give insight to its applicability for any function.

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