EICR help

[JohnW2]

Non-ferrous locknuts should be used.

Yes, that obviously goes wthout saying ...

Actually, I think I'm probably being silly. Eddy currents will be induced in any conductor, won't they, regardless of whether or not it is a ferromagnetic material?

Kind Regards, John

 

[SaladFingers]

You mention mainly Triple pole machinery so maybe the neutral was added at a later date hence the harmonised.

Is it possible to revert it back to a Triple pole board and use the Two core to supply a new single phase board, thats assumiong theres no Tpn loads, however even supplying a smaller Tpn supply for them alone could be cheaper than a new 35mm 4 core

TP = Three phase, not tripple pole. Just pointing that out (no bickering intended).

 

[333rocky333]

securespark maybe able to clarify, the enclosure slots were in the 14th regs and possibly earlier and were in them days mainly for when single core pyros entered the enclosure,

 

[ricicle]

TP = Three phase, not triple pole. Just pointing that out (no bickering intended).

 

[SaladFingers]

TP = Three phase, not triple pole. Just pointing that out (no bickering intended).

 

[SaladFingers]

securespark maybe able to clarify, the enclosure slots were in the 14th regs and possibly earlier and were in them days mainly for when single core pyros entered the enclosure,

You'd still use it now if necessary. Some applications use single core cables still. In the middle of a job now with single 120mm H07 cables. Another way around it is a brass gland plate or tough plastic gland plate.

 

[JohnW2]

securespark maybe able to clarify, the enclosure slots were in the 14th regs and possibly earlier and were in them days mainly for when single core pyros entered the enclosure,

You'd still use it now if necessary. Some applications use single core cables still. In the middle of a job now with single 120mm H07 cables. Another way around it is a brass gland plate or tough plastic gland plate.

The only situation in which I can see that slots (joining the holes) would work would be if single cores (or, at least, separated L's and N) passed through separate holes in a metal enclosure through non-conductive grommets or glands. As I recently wrote, I suspect that the material is a bit of a red herring - one will get eddy currents in a brass plate (or, indeed, the brass body of a gland) just as one can in a steel enclosure, won't one?

Kind Regards, John

 

[333rocky333]

Non-ferrous locknuts should be used.

Yes, that obviously goes wthout saying ...

Providing the nuts dont touch or bridge the slot i cant see the point in non ferrous locknuts, as surely its no different to the body of say a pyro gland protruding the enclosure.
I personally dont remember the theary behind the slot unfortunately, but in my apprenticeship i seem to recall witnessing a few 4 single pyro supplies entering slotted enclosures with standard black enamel locknuts

 

[RF Lighting]

You mention mainly Triple pole machinery so maybe the neutral was added at a later date hence the harmonised.

Is it possible to revert it back to a Triple pole board and use the Two core to supply a new single phase board, thats assumiong theres no Tpn loads, however even supplying a smaller Tpn supply for them alone could be cheaper than a new 35mm 4 core

The DB is running machines like a press brake and a guilotine. Whilst the bulk of the load is TP motors, there are auxilary bits on the machine that do require a neutral such as lights. Not sure if the control is SP&N or if it's 400V two phase.


It looks as though there were two TP dist boards in the factory originally. One has been converted to SP&N and supplies the factory offices, which is fine, and the other is this one.

There are two other TP&N submains which are wired up in newer 4 core SWAs.

You'd still use it now if necessary. Some applications use single core cables still. In the middle of a job now with single 120mm H07 cables. Another way around it is a brass gland plate or tough plastic gland plate.

I did wonder about a paxolin gland plate, bit it still doesn't get over the loop caused by the armoured.

I remember hearing about slots years ago, but I now realise this was only OK for pyro (non-ferous sheath) and singles passing through individual holes.


I once saw a job where the main incommer was 400A TP&N. The main isolator was fed in singles in steel trunking from the CT chamber. There was a seperate bush from the trunking to the isolator for each tail. The whole switch used to hum when the loading got a bit high.

 

[ricicle]

The only situation in which I can see that slots (joining the holes) would work would be if single cores (or, at least, separated L's and N) passed through separate holes in a metal enclosure through non-conductive grommets or glands. As I recently wrote, I suspect that the material is a bit of a red herring - one will get eddy currents in a brass plate (or, indeed, the brass body of a gland) just as one can in a steel enclosure, won't one?

Kind Regards, John

Eddy currents are not induced into non-ferrous metals as there are no magnetic fields in them.

 

[JohnW2]

Eddy currents are not induced into non-ferrous metals as there are no magnetic fields in them.

Eddy currents are surely simply currents induced in any conductor subjected to a changing magnetic field? If what you said was right, how could a generator with coils made of copper wire work? ... or how could an induction hob work with aluminium pans?

Kind Regards, John

 

[JohnW2]

Providing the nuts dont touch or bridge the slot i cant see the point in non ferrous locknuts, as surely its no different to the body of say a pyro gland protruding the enclosure.

As you will have seen,once I started thinking I retracted my agreement with the comment about non-ferrous nuts. I don't think the material is relevant, if it is a conductor.

I personally dont remember the theary behind the slot unfortunately, but in my apprenticeship i seem to recall witnessing a few 4 single pyro supplies entering slotted enclosures with standard black enamel locknuts

As I've said, the slot (between holes) would make total sense if singles were passing through separate holes without metal-bodied (or metal-nutted/washered) glands.

Kind Regards, John

 

[333rocky333]

As I've said, the slot (between holes) would make total sense if singles were passing through separate holes without metal-bodied (or metal-nutted/washered) glands.

Kind Regards, John

John, not disputing you as you seem more knowledgable than me but how would that make a difference, surely the addition of the gland passing through would be similar to just the conductor going through, albeit a slightly larger diameter feild.
The slot then altering that feild around that conductor and gland no different to just the conductor

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• 333rocky333
• 27 Jan 2013
• 1

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• 333rocky333
• 27 Jan 2013
• 1

 

[JohnW2]

As I've said, the slot (between holes) would make total sense if singles were passing through separate holes without metal-bodied (or metal-nutted/washered) glands.

John, not disputing you as you seem more knowledgable than me but how would that make a difference, surely the addition of the gland passing through would be similar to just the conductor going through, albeit a slightly larger diameter feild.

Perhaps I wasn't very clear - because, indeed, the gland is irrelevant, provided it's non-metallic. Going through a plastic gland or grommet is just the same as going through a hole in the metal (without any protection or stress relief).

The slot then altering that feild around that conductor and gland no different to just the conductor

As I see it, the field is not the issue - what matters is the conductive path available for eddy currents to flow through (no conductive curcuit = no eddy current, regardless of fields). If you have two singles (e.g. L & N of a 1-phase cct) going throughg separate holes in a metal enclosure (with or without plastic glands/grommets), then there will be a complete metallic path encircling each of those singles in which induced eddy currents can flow as a result of the (unopposed) field created by current in each of the singles.

If you cut a slot between the two holes, then there is no complete conductive path around either of the individual holes, so there can't be eddy currents flowing around either of the holes, individually. The only eddy current path is (with the slot) that which goes around both of the holes. However, given that the fields in the L & N will 'cancel', the net eddy current around both holes should be zero (just as if one put a 2-core L&N through the same hole in the enclosure). Looked at another way, as far as conductive paths (for eddy currents) are concerned, the slot converts the two holes into one, and there is no 'net' (vector added) current going through the two cores which go through that 'one' hole.

Does that make sense?

Kind Regards, John

 

[JohnW2]

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• 333rocky333
• 27 Jan 2013
• 1

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• 333rocky333
• 27 Jan 2013
• 1

You slipped this in after I replied to your post! As I hope what what I wrote explained, those are the very situations in which I think the slots are a totally logical solution, for the reason I gave - the slots break the electrical paths in the metal around each conductor, thereby preventing eddy currents flowing around the conductor as a result of the induction from the field it creates. With slots, the only eddy current which can flow is that around the whole group of holes, but the net field should then be zero (whether L+N or 3P+N), hence nothing induced.

Kind Regards, John