A solution for eddy currents

[Brightspark2]

Need to provide a 3 phase supply from an MCCB board to a changeover panel. The MCCB board and changeover panel are side by side connected by 3 x 50mm brass bushes. The brass bushes have around 13inches (In old money) vertical between them.

Now we can only get 2 wires through each hole (120mm single core). Would 1 phase and neutral through one hole and 2 phases through the other hole still present a problem with regards to eddy currants, remembering these are about 13inches apart.

After advice before we start looking at how we can cut a panel out on an energized DB.

Hope thats clear...

 

[Guitarist]

One hole or slot between

 

[Brightspark2]

Are you not going to kill power for connecting anyway if you can swap cables between holes? You need to get them through 1 hole or slot between.

Where installing the cables, that will be wired to an MCCB, the MCCB board will remain energized the changeover panel wont be energized until we switch it on obv...

What do you mean by slot between?

I was afraid of that but just wanted to confirm before we start looking at other options, to which there are few lol...

Looks like we will have to cut a square hole in somehow to which they can all go through, not going to be easy with it in situ and the MCCB board energized.

 

[Guitarist]

If you can get one big hole for all the cables, then job done. If not, by cutting 2 slots between the holes, you will stop the eddy currents from "circulating". Think of it like a break in the circuit.

 

[johnboy6083]

As above, it's got to be one hole or a slot cut between the holes. Can you get a jigsaw in there without damaging anything?

 

[Brightspark2]

Aahhh my collage years are coming back to me, I remember about the slots between the holes now...

I think we could get a jigsaw in there, this seems like the solution...

Thanks for the advice men...

 

[Deleted member 26818]

Make certain that the brass bushes also have brass nuts, not steel.

 

[Knobhead]

As spin says brass lock nuts to go with the bushes. I had a 1000KVA transformer fail due to a contractor using steel nuts.

 

[Guitarist]

Or use a plastic nut.

 

[Knobhead]

Cheapskate

 

[Guitarist]

Cheapskate

Haha, never.
I can just see them getting to the job and realising that they have no brass nuts, so rather than leave the steel ones installed, plastic is the other option. :icon3:

 

[Andy 7671]

Make certain that the brass bushes also have brass nuts, not steel.

Any chance of expanding on this a little please, without an argument itll just be "It dont really matter, use what your given"

What about a distribution board surrounded by trunking, bushed, instead of letterbox slot, presumably they should be the same.

The same should hold true for glanding as well dont you think...?

Hope you dont think Im hijacking OP

 

[johnboy6083]

for glanding multicore cables, its not a problem using steel locknuts, as al pahses and neutral are contained within the hole. If you were to use sngle core armoured cables, then the armour will be aluminium, and the gland/locknut will be too!

 

[Brightspark2]

Make certain that the brass bushes also have brass nuts, not steel.

As spin says brass lock nuts to go with the bushes. I had a 1000KVA transformer fail due to a contractor using steel nuts.

Or use a plastic nut.

Is this to also reduce the chance of eddy currants because of the higher resistance of steel?....

We do have brass lock nuts...

 

[Knobhead]

Brass is non-magnetic, steel is. It’s the current set up by the magnetic flux that causes the problems.