Separate fuses for 3phase supply

[James sparks]

Hi All,

Just trying to double check if there's a reg suggesting a 3phase circuit should have over-current device that disconnects all line conductors at once? Got an old rewireable board supplying 3phase motors with 3 individual fuses.

I'm looking at 530.3.1 ...................

Can anyone confirm this?

Thank!!

 

[Pete999]

Not all three phase circuits are protected by a device that disconnects all three phases, you said in your post that you have a large rewireable D/B thats quite common in industrial installations, most final circuits (three phase motors for example) would have their own individual protection, which would sense an over current in one of the phases. should one of the main phases go open circuit 530.3.1 deals with this scenario (a contactor motor starter) as an example. Your board should supply the motors via a starter.

 

[Engineer54]

Agree as Pete999 has stated...

There are 3 phase switch fuses/fuses switches etc, that use special striker fuses, that release a short rod. So that when any of the fuses operate, the released fuse rod hits a striker plate that opens the load contacts to all 3 fuses.

 

[gnuuser]

something like this (overload heater block)
we are phasing them out in some of the older equipment in our plant
damn things are a pain to find.