Single core cable entry into metal enclosure

[ShaneR]

Hi all

When single core power cable(s) would enter into a metal enclosure we used cut a square hole and cover it with a large aluminium plate then drill holes through that.

Its this still a requirement?

Does it make any difference?

Thanks

[JamieP]

I believe it's to do with Eddy Currents, don't know a lot about it myself but section 3.9.10 covers it I believe

[PeteRig]

Yeah still a requirement, electrical theory doesn't change, as Jamie has pointed out covered in section 3.9.10.
Slotting metal or fitting AL plates "Stops eddy and his mates"
AL plates make it easy to drill out for the cable glands, remove the plate from the board and no mess inside the board!

[ShaneR]

Thanks for that

I had a read, I didn't know that the slot width is proportional to cable size (20%).

Question: Does single TPS cable(s) need to be run in trefoil?

Looks like single core neutral screen does

[AlecK]

Whenever you're intending 3-phase supply spread across multiple cables, you should take steps to minimise the possible adverse effects of the overall electromagnetic fields. The higher the current; the more important this is.

[Sarmajor]

There is no logical electrical reason to trefoil single core N/S cables. The magnetic fields of these currents are cancelled by the neutral screen.

[ShaneR]

There is no logical electrical reason to trefoil single core N/S cables. The magnetic fields of these currents are cancelled by the neutral screen.

Have a look at 3.9.10.3

[AlecK]

1C +N/S is not a "single-core" cable; it's a form of multi-conductor cable.
Refer also clause 3.3.5 of "3008.1.2; which says how N/S is to be treated for establishing CCC.

And the screen is not a "metal sheathing". 3.9.10.3 covers things like MIMS cable.