Running wire to terminal through a 1/8 inch metal plate in the cabinet. that had the holes cut out and insulated with rubber,

[mac380abc]

Running wire to terminal through a 1/8 inch metal plate in the cabinet. that had the holes cut out and insulated with rubber, the wire size is 4/0 and there are 3 wire per phase. we have the 480 v 3phase B O Y..We brought all 3 brown cables through one of the holes
then did the exact same thing for the Ornge cables and the Yellow cables. Someone had told us that we need to put one of each color through each hole, otherwise it will generate too much heat. I can see in conduit, but not through a sheet metal plate with each hole insulated. Would this be a problem, or are we getting false information. Also is this a code requirement?

 

[infinity]

You need to cut a slot between all of the holes if the plate is ferrous metal.

 

[LarryFine]

The information is correct. The insulation bushings don't matter. The problem is induction, not conduction.

There was another thread recently where the wire was overheating where it came through individual holes.

 

[MD Automation]

As Larry mentioned above, the problem is not heating from IxR losses - but rather the effect of inductive heating.

Any current carrying wire creates a magnetic field around it.

Passing a single current carrying wire thru a ferrous hole will cause that magnetic field to induce Eddy currents that circulate in the metal and heat it up.

If all the current carrying wires (like in a 3 phase group) pass thru the same hole - then the total currents tend to cancel out and the magnetic field is no longer an issue. Like if you put an amp clamp around all the conductors, you will measure zero amps. Everything cancels.

So... if you have to pass wires thru a set of separate holes, the slot cut between the holes tends to make them all "look" like a single hole. Granted, it's an "odd looking" hole, but to the magnetic fields that want to create circulating eddy currents, it's still just a (weird) single hole.

 

[LarryFine]

Another solution is to pass all of the wires through a plastic panel installed in a single large hole in the cabinet like a window.

 

[mac380abc]

The reason for the 1/8 Metal panel was to hold the cool air inside, as this was all open and the cool air would seep to the bottom of the rectifier, thereby causing a premature shut down on an overheat. there are 6 4/0 cables per phase,
and we have 3 slotted holes in which the wires run up through, each slot has 6 cables for that phase, They requested that we put 2 wires from each phase in each slot, where now we have each slot having cables from 1 phase. Someone thought this would generate heat as it does if we did this in a conduit, but I don't believe this to be the case. to solve for the present, we just installed thermocouples wired to monitors to see what kind of temps we have in those areas
of concern... Thank you for all your feed back...

 

[jim dungar]

The reason for the 1/8 Metal panel was to hold the cool air inside, as this was all open and the cool air would seep to the bottom of the rectifier, thereby causing a premature shut down on an overheat. there are 6 4/0 cables per phase....

You could cut really narrow slots and then seal them with caulking or a non-ferrous cover plate.