Discuss Eddy current clarification in the UK Electrical Forum area at ElectriciansForums.net
Yes aluminium is a good conductor, so eddy currents will be greater than if it were steel.
Whether in practice anything bad could happen I'm not sure
Seems I am mistaken - thanksUnless I'm very much mistaken the issue of eddy currents only materialise in ferrous materials. Gland plates are often made of aluminium where large singles are brought into an enclosure.
The first picture I assume is steel in which case it is wrong.
You are not mistaken, eddy currents (Foucault currents) will be induced in any conductor within the presence of a changing magnetic field.Seems I am mistaken - thanks
Has anyone found much difference in temperature when it’s only the CPC which goes through a separate hole? Line and neutral conductors going through together.
From memory though doesn’t the reg also say “and the appropriate earthing conductor” should enter through the same hole?
I have to say though, we designed MV and HV switchgear for typical currents of circ 630 - 3000 A and using 1/4" steel plate we used separate apertures for each phase, and only added around 5-10 deg C temperature rise!
I hope you have many 100's amps available in your workshop!I've been meaning to experiment with this for a while, maybe I'll get some time in the workshop soon.
I hope you have many 100's amps available in your workshop!
Not borne out by John Ward's video, or Julie's experience. I'm just perplexed now!Nope, and shouldn't need much current either.
I recall Lucien mentioning that he made a simple square of conduit with a lampholder in the middle of one side and a mains input opposite it which got very warm with the live routed through one side and the neutral through the other with just a 100W lamp in it.
I guess the other side of that is it might add some impedance to the system due to inductance, making the AC R2 a bit higher than the DC one measured during dead testing to verify conductors are properly speced and installed.Yes it does, I think this is down to the fact a lot of current can flow through it under fault conditions.
Not borne out by John Ward's video, or Julie's experience. I'm just perplexed now!
Ah! OK - Sorry I didn't get that at all. Re-reading your post I see what you mean. Thanks.But both of those examples are cables passing through steel plates whereas I was talking about cables passing through a few feet of steel conduit.
I always thought they had the same effect on brass as I was once told brass bushes wouldn’t prevent the issue or is that because the brass bushes are drilled and fitted to the steel casing of a distribution board?Eddy currents are a real thing, I have seen several instances of damage by them.
The worst case was on the LV box of a 2MW transformer, four conductors per phase all neatly grouped by the phase and taken through a steel plate. The paint on the plate had burnt off around the cables and discoloured the steel. We changed the gland plate to brass to solve the problem. Interestingly at the other end the singles were again taken through steel into the switch board but there was no sign of heating, I think this was due to the singles being taken in randomly rather than bunched in phase groups.
As said above there will always be induced currents from singles but it is much worse if they pass through ferrous metal. In another case we had four singles passing through a steel plate, again there was signs of heating. This was solved by cutting a slot to link the four holes (which were in a line) then brazing it shut again to retain strength. The brass in the brazed joint was enough to prevent further eddy current damage.
It is conductive but not magnetic. The braze stops the magnetic circuit and forces the magnetic flux from all the cores to go around all four cores. The sum of all the cores should be zero so there is no magnetic flux left to induce currents.would not a brazed up slot still count as a shorted turn of a transformer os sorts?
You are correct. Brass bushes in a steel plate will not make any difference. You have to look at the magnetic circuit, all the cores have to pass through the same hole in any ferrous material.always thought they had the same effect on brass as I was once told brass bushes wouldn’t prevent the issue or is that because the brass bushes are drilled and fitted to the steel casing of a distribution board?
That is correct, A changing magnetic flux will induce current in a conductor, but by putting all the cores through the on hole in a ferrous material the magnetic fluxes cancel out, hence no induced current.I thought any conductive material in a moving magnetic field will induce a voltage.
Magnetic flux is a thing but it's the moving flux or conductor moving though a magnetic field that induces a voltage.
Surely my 1.5mm and 2.5mm earths going through their own hole will be OK then?I remember working at the large Debenhams in Manchester city centre and they had installed a new sub panel in 600.0 singles on a tray. They entered the existing panel through separate entries of the ferrous panel and it was buzzing like crazy but there was no heat build up.
Your NIC inspector probably doesn't understand the science.Surely my 1.5mm and 2.5mm earths going through their own hole will be OK then?
Complete opposite end of the spectrum!
Wonder if my NIC inspector would be have hard feelings about it
Your NIC inspector doesn't understand
Hi i dont know if this is the right place for this question here goes, can eddy currents be used to to 8dentify diffrent metals? Tia.The first picture I assume is steel in which case it is wrong. The aluminium panel in the second picture is fine but the lock nuts assuming they are steel are not.
Just annoying when you’re a bit of a neat freak with a distribution board and know that taking the earths through their own hole at the top of the board makes it look so much better
Hi i dont know if this is the right place for this question here goes, can eddy currents be used to to 8dentify diffrent metals? Tia.
I would imagine by not being able to identify what earth lead applies to what circuit, unless each earth lead is identified/labelled.How so?
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