What is inverse time tripping? Are circuit breakers inverse time trip?

Issue:
What does it mean when a circuit breaker is described as an "inverse time" trip breaker?

Product Line:
Circuit Breakers

Resolution:
Inverse time tripping is a characteristic of circuit breakers in which the breaker trips in more time with lower overcurrent, and less time with higher overcurrent. For the US, Article 100 of the National Electric Code defines it as follows: "Inverse Time (as applied to circuit breakers). 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."

All Schneider Electric/Square D/Merlin Gerin Circuit Breakers and Supplementary Protectors are inverse time trip (excludes Molded Case Switches and Motor Circuit Protectors).

NOTE:  Delays are introduced into the overload trip function to minimize the risk of nuisance tripping for transient overloads such as when starting a motor or energizing a transformer.  The breaker's tripping characteristic is always designed to protect rated wire and to comply with the UL 489 and other applicable standards.

Released for:Schneider Electric New Zealand