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Need to provide a 3 phase supply from an MCCB board to a changeover panel. The MCCB board and changeover panel are side by side connected by 3 x 50mm brass bushes. The brass bushes have around 13inches (In old money) vertical between them.

Now we can only get 2 wires through each hole (120mm single core). Would 1 phase and neutral through one hole and 2 phases through the other hole still present a problem with regards to eddy currants, remembering these are about 13inches apart.

After advice before we start looking at how we can cut a panel out on an energized DB.

Hope thats clear...
 
for glanding multicore cables, its not a problem using steel locknuts, as al pahses and neutral are contained within the hole. If you were to use sngle core armoured cables, then the armour will be aluminium, and the gland/locknut will be too!


5 times I read that,

First I was thinking..jeez is this some kind of galvanic deposition, then I realized when you said the gland and locknut will be aluminium you meant exactly what you stated, you will be given aluminium gland and locknut to use.

Ho hum...time to put my Kermit outfit on again.
 
Brass is non-magnetic, steel is. It’s the current set up by the magnetic flux that causes the problems.


I know by mixing these materials it can cause corrosion issues due to the potential difference that occours between them.

Is this what your reffering to? or could you eloborate a bit more, why did the transformer fail?...
 
I know by mixing these materials it can cause corrosion issues due to the potential difference that occours between them.

Is this what your reffering to? or could you eloborate a bit more, why did the transformer fail?...

I will take a guess before Tony brings on his exoertise,large eddy currents were generated that caused overheating in the laminates and eventually melted the windings


Eddy currents are welcome little features ,those transformer laminates help generate the heat that keep the good folk warm when the fingers are freezing

Never mind save the Amazon and save the Whale,we need to save the Eddy currents
[ElectriciansForums.net] A solution for eddy currents
 
could you eloborate a bit more, why did the transformer fail?...

I would like to learn as well.. I understand the principle behind it, and always bring phases an N through one entry, and my answer is because of eddy currents, which i understand. but in a real practical hi current situation could you please elaborate. thx
 
Well eddy currents create heat. In high current applications this can cause the ferrous metal to become cherry hot. This can cause transformer laminations to fail, which will of course cause eventual shorts in the transformer windings. Motors would suffer similar problems. When I am required to install tails into switchgear, and stuffing glands are specced, then I cut a large slot from the steel gland plate. I then cut paxoline larger than this hole, and gland onto that. This maintains any IP rating (often for virmin in the water industry), and looks better.
 
It was the LV terminal box that failed. Where the transformer tails (singles) passed through the gland plate. The contractor had used the brass glands we provided but pocketed the brass lock nuts and used steel. As the load on the transformer increased the locknuts just got hotter until the cable insulation failed..
 
I don't mean to sound rude here, but if anyone interested just googles "eddy currents", there are loads of articles and threads. :wink_smile:

Yes there are, but there is no substitute for first hand experience in the field.

I premised my enquiry with "I think I need to do further reading" so a link would surfice.

Too busy in the day, but I guarantee when I do search it will be mostly theory.

I also thought the more intellectual members would relish a different subject to talk about.

TBH I do find your post rude if you dont want to enhance my knowledge fine, click off the subject.
 
I don't mean to sound rude here, but if anyone interested just googles "eddy currents", there are loads of articles and threads. :wink_smile:


There sure is, they explain eddy currants, which I know about otherwise I wouldnt of realised they would cause a problem, I was after a pratical soloution other than cutting a hole for them all to go through, to which I got one.

Tony also gave first hand experiance of these causing a problem, which we wanted to more about, all well a good knowing the theory of eddy currents but even better when you know of problems these have caused first hand. You relaise how much of a problem they can actually be, or how much of a problem putting a steel nut on a brass bush in this situation can actually cause.
 
I did actually contribute in a positive way right at the start of this thread!!!
The subject then became more in-depth and I considered that the materials online would be more beneficial than asking forum members to spend ages trying to explain something which is explained quite succinctly in various articles. I'm sorry that you found that observation rude Andy, and I will be careful who I try to help in future.
 

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