RonShap
Electrical
- Aug 15, 2002
- 230
Consider a 1600A current limiting fuse with 200kA available short circuit current on the line side.
The fuse manufacturer states that the maximum let-through at any current up to 200kA on the line side is less than 100kA on the load side.
Why is a series rating required for a downstream 100kAIC rated circuit breaker located within a few linear feet of cable (other than just the code requires it)? The breaker can never see more than 100kA since the fuse will never let more than that through?
It doesn't make sense to me. Any amount of dynamic impedance downstream of the fuse will only reduce the fault current and the resulting let-through even further below 100kA.
The fuse manufacturer states that the maximum let-through at any current up to 200kA on the line side is less than 100kA on the load side.
Why is a series rating required for a downstream 100kAIC rated circuit breaker located within a few linear feet of cable (other than just the code requires it)? The breaker can never see more than 100kA since the fuse will never let more than that through?
It doesn't make sense to me. Any amount of dynamic impedance downstream of the fuse will only reduce the fault current and the resulting let-through even further below 100kA.