MV Switchgear Fuse

[EngTips202506]

I've got a MV switchgear where the three phase transformer is 63kVA (240V), where the service voltage is 22kV and bus rating is 630A. I downsized the fuse rating from 20A to 10A since 20A is oversized. Can I change it to 6.3A? According to this table, the minimum I could go is 10A.

 

[mparenteau]

Who knows? Did you look at how the fuse performs at 12x @ .1 sec and 20x @ .01 sec (I have seen 25x @ .01 sec as well)?

Mike

 

[waross]

What Mike said.
Apart from that; There is not enough information.
In North America this is a code issue and may be subject to conditions of secondary protection.