tripping time of Current limiting circuit breakers and fuses 2

[victa1288]

I am working on International project based on IEC standards. But I don't have data for tripping times of Current limiting circuit breakers and fuses.

Some people said it is 1/2 cycle. Other people said it is 1/4 cycle.

I would apprecite it if anybody here can provide me more acurate infomation.

 

[davidbeach]

It can only be current limiting if the interrupting time is less than 1/2 cycle. At exactly 1/2 cycle there is no limitation, at just under 1/2 cycle there isn't much limiting. The greatest amount of limiting will happen with interrupting times around 1/4 cycle. The exact time will depend on the magnitude of the fault current and the characteristics of the device.

 

[dpc]

I agree with David - it has to be faster than 1/2 cycle to be current-limiting - but remember - it isn't always going to be current limiting - that depends on the current magnitude. If you look at the fuse curve and based on your fault current the clearing time is 2 cycles, there is no guarantee of current-limiting.