AusLee
Electrical
- Sep 22, 2004
- 259
Hello,
Merlin Gerin says that if the input breaker is an MCCB of frame 100 equiped with a magnetic of trip unit 100, then if the downstream circuit breaker is an MCB Multi9 C60 32A, the selectivity is as follows:
If the fault current is less than 800A, total selectivity is acheived. If the fault current is more, then both breakers may trip.
My question is: what can be done to achieve total selectivity? I know that it depends on how critical the application is and if it is really worth the extra cost of equipment, but what are these equipment in the first place? should each circuit be accompanied by a special relay and all circuit breakers must be equipped with a tripping mechanisms?
Merlin Gerin says that if the input breaker is an MCCB of frame 100 equiped with a magnetic of trip unit 100, then if the downstream circuit breaker is an MCB Multi9 C60 32A, the selectivity is as follows:
If the fault current is less than 800A, total selectivity is acheived. If the fault current is more, then both breakers may trip.
My question is: what can be done to achieve total selectivity? I know that it depends on how critical the application is and if it is really worth the extra cost of equipment, but what are these equipment in the first place? should each circuit be accompanied by a special relay and all circuit breakers must be equipped with a tripping mechanisms?