Circuit breakers Icu and Ics

Update date:2018-03-05 Source:MAXGE

Circuit breakers Icu and Ics

 Ultimate short circuit breaking capacity Icu is under specified conditions (voltage, current, power factor, etc.) circuit breaker breaking capacity, and after breaking does not consider whether the circuit breaker can continue to carry its rated current. Icu This parameter characterizes the circuit breaker's ultimate breaking capacity and is also a destructive test for circuit breakers.


  The ultimate short-circuit breaking capacity Icu test procedure is: O-t-CO, that is open - delay - open immediately after closure. Here t delay rest time is generally not less than 3 minutes.Test circuit in the O program, the circuit breaker is disconnected. When the CO test circuit breaker closing, and then immediately cut off. Closing here is to check whether the breaker is damaged by the electric repulsion impact and thermal shock caused by the peak current after it has been subjected to the on-current (peak current). If the circuit breaker can be opened immediately after switching on and the arc can be extinguished, the CO test of the circuit breaker is successful.


  Running short-circuit breaking capacity refers to the breaking capacity of the circuit breaker under specified conditions (voltage, current, power factor, etc.), and the circuit breaker can continue to carry its rated current after breaking. This shows that Ics characterizes the circuit breaker's ability to repeatedly trip.The test procedure for running short circuit breaking capacity Ics is: O-t-CO-t_CO, ie open - delay - open immediately after closure - delay - open immediately after closure.Compared with the test procedure of Icu for ultimate short-circuit breaking capacity, there is one more CO for the test procedure for running Ics for short-circuit breaking capacity. When the test is successfully completed, but also need to do frequency withstand voltage verification, temperature rise verification, overload release performance verification and operational performance verification. Operational performance verification is loaded at the same operating voltage rated current, so that the number of repeated operation of the circuit breaker for electrical life of 5%. Test criteria for the passing of the test are: Each test procedure is qualified, and the circuit breaker housing should not be broken, but allows cracks.


  For users, maybe more emphasis on Ics. For the switchgear manufacturer, Icu is more important. Switch by Icu optional, can reduce manufacturing costs.

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