Single core conductors passing through a ferrous metal

2011

I know that single core AC conductors are not permitted to pass through a ferrous plate unless certain conditions are met (due the heating effect that can be caused by circulation of eddy currents).

There is quite a bit to be found on the interweb about it.
I was even on a job where the thermal effects caused a cable on the secondary side of a large transformer to melt!

My question is, can anyone show me where this is mentioned in the regulations (ET:101)??

I have found mention of it in the "17th Edition Wiring Regulations"

Many thanks.

M cebee

yes i think circ currents can be an issue with single core armoured cables

if they're glanded both ends

2011

M cebee wrote: »

yes i think circ currents can be an issue with single core armoured cables

if they're glanded both ends

You are correct that this can be a problem. It is discussed here

The problem I am talking about is:

The use of a ferrous gland plate appears to be a violation of section 300.20(B) of the National Electrcical Code.
"( Individual Conductors. Where a single conductor carrying alternating current passes through metal with magnetic properties, the inductive effect shall be minimized by (1) cutting slots in the metal between the individual holes through which the individual conductors pass or (2) passing all the conductors in the circuit through an insulating wall sufficiently large for all of the conductors of the circuit.


This is why brass and aluminum gland plates are used when single core conductors have to pass through them.

M cebee

figure D5.3 on your link shows the problem of eddy currents on the ferrous plate

M cebee

521.5.1

page 79 covers it

2011

figure D5.3 on your link shows the problem of eddy currents on the ferrous plate

Yes, I know.
I have found lots of reports and information about this and I understand the principle of the issue clearly.

What I can't find is a mention of it in ET101, although I know it is in there somewhere which is why I started this thread.

As far as I can remember there was even a drawing of it in an older edition of the ergs. It showed 4 single core conductors passing through a plate with a slot cut between them.

M cebee

yes it's there:D page 79

2011

M cebee wrote: »

521.5.1

page 79 covers it

Great, I must take a look.

Thanks!

2011

Just checked, you are correct. Just what I needed.

Many thanks.

I wish there was a soft copy of the ergs. It would make searching much quicker.

Bruthal

2011 wrote: »

Yes, I know.
I have found lots of reports and information about this and I understand the principle of the issue clearly.

I`d be shocked and horrified if you didnt:D:D

2011

robbie7730 wrote: »

I`d be shocked and horrified if you didnt:D:D

Yes

Will tell you a story about it by PM