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Entry type: FAQ Entry ID: 21654427, Entry date: 02/21/2018
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3RV1/3RV2 Circuit Breaker: Are Definition of selectivity categories A and B concerning circuit breakers

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This entry contains information about inscription 'CAT A'

QUESTION:

The label on 3RV1 and 3RV2 MSPs bears the inscription 'CAT A'.
What does this mean?

 


ANSWER:

The inscription 'CAT A' on the labels of 3RV1 and 3RV2 MSPs refers to the selectivity category acc. to section 4.4 of IEC 60947-2.

Selectivity category A means:
Circuit breakers not specifically intended for selectivity under short-circuit conditions with respect to other short circuit protective devices in series on the load side, i.e. without an intentional short-time delay provided for selectivity under short circuit conditions, and therefore without a short-time withstand current rating Icw.
Selectivity category A usually applies for current limiting moulded-case circuit breakers (e.g. 3RV1 and 3RV2)

Selectivity category B means:
Circuit breakers specifically intended for selectivity under short circuit conditions with respect to other short circuit protective devices in series on the load side, i.e. with an intentional short-time delay (which may be adjustable), provided for selectivity under short circuit conditions. Such circuit-breakers have a short-time withstand current rating Icw.
Selectivity category B applies for zero-point quenching air circuit breakers with an adjustable short-time delay of the short-circuit release (e.g. 3WL1).
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