HOT FLOOR!

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ROBOJOE77

ROBOJOE77

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troutdale oregon
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manufacturing plant journeyman
We have a metal deck built around a vessel. Below is the area that the power supplies send 25V and 6000A through a large single conductor that travels through an opening in the floor up to the electrodes for each set of heaters. The metal decking and metal framing members get hot due to what I am assuming is the inductance from the magnetic field of the conductor passing through the opening in the floor. It gets to a little more than 100o in some spots. How do we mitigate this? is there a CEMF being created in the structure surrounding the conductor. Can this create an impedance? Is it just science and kinda cool?
 
Is this AC or DC? 6000 amps is going to create a big magnetic field. If it's ac I can see it creating currents on anything conductive near it

Is this some kind of EAF for melting metal?
 
Joethemechanic said:
Is this AC or DC? 6000 amps is going to create a big magnetic field. If it's ac I can see it creating currents on anything conductive near it

Is this some kind of EAF for melting metal?
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It's AC. I can't remember if it's a code thing or just a theory thing where you can cut slots in the metal to break up currents, but I don't know about cutting into structural steel.
They are high temp vacuum vessels for purification of graphite parts
 
If you cannot put slots between the holes, can you run both polarity conductors for each heater through the same hole (enlarged if necessary)? That way the net current will be zero and there will be no large induced current or magnetic hysteresis losses.
 
How is the conductor from the other phase of the AC power supply being routed over to the electrodes?
Is one phase of the supply output grounded, and if so, is it possible that it's grounded in more than one place?
 
Joethemechanic said:
Well that is why transformer cores are made out of laminations and not one chunk of steel
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No. The lamentations in a transformer core are for dealing with the intended magnetic field.

The slots mentioned by the OP are intended to interupt an unwanted magnetic path.
 
Clint Taurus said:
It's AC. I can't remember if it's a code thing or just a theory thing where you can cut slots in the metal to break up currents, but I don't know about cutting into structural steel.
They are high temp vacuum vessels for purification of graphite parts
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It is both code and theory. A single conductor completely surrounded by a steel path will experience induced heating. The only solution is to break the magnetic path which is the purpose of the slots, or route the supply and return conductors through the same path.
 
No. The lamentations in a transformer core are for dealing with the intended magnetic field.

I was always told to be careful not to bang up laminations on the edge so as not to allow them to short together, because if they shorted together the currents would cause overheating. You mean I have been super careful assembling electric motors the last 40 some years for no good reason?
 
Joethemechanic said:
No. The lamentations in a transformer core are for dealing with the intended magnetic field.

I was always told to be careful not to bang up laminations on the edge so as not to allow them to short together, because if they shorted together the currents would cause overheating. You mean I have been super careful assembling electric motors the last 40 some years for no good reason?
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No. You have been doing the right thing
The laminations often have some amount of varnish/separation between them so if they are damaged the performance of the core can be affected, with overheating as one of the results.

It is just that in a motor/transformer we want a magnetic path while in the OP case we don't want one.
 
What is the function of lamination in motor?


Motor laminations form the core of an electric motor's stator and rotor. They consist of thin metal sheets that are stacked, welded, or bonded together. By making them from individual pieces of metal rather than a solid pieces, they experience less eddy current losses.
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Is there some reason the laminations in a transformer serve a different function? I always just assumed they did the same thing. I know the armature of a DC motor is made out of laminations because the currents in it are AC, But the pole shoes that hold the fields are solid because the current in the field is DC. or at least that is what I was taught
 
Clint Taurus said:
Below is the area that the power supplies send 25V and 6000A through a large single conductor that travels through an opening in the floor up to the electrodes for each set of heaters.
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If each element has two conductors, you need to cut a slot between them. If each element has one conductor and uses the vessel, you need to cut a slot between each conductor and the vessel. You should be able to use non-conductive material to replace any necessary structure.
 
Actually the laminations/slots don't break up the magnetic path (magnetic flux travels just fine through air), rather the slots/laminations break up the available path that electric current can follow.

Going back to the OP, the idea is to cut slots so that balanced sets of conductors end up effectively in the same hole electrically. While you can't cut a slot through the structural members supporting the floor, you might be able to cut slots in the flooring, and use insulated mechanical connections for the structural members. For example the flooring could sit on insulating material on top of the structural members, and the bolts holding the structure together could pass through insulating bushings and washers.

The design of this will need to include making sure that everything remains properly grounded/bonded, while breaking up any conductive loops around high current conductors.

-Jon
 
winnie said:
It sort of went back and forth, I think you said initially that the laminations break up currents, then were corrected to say they break up the magnetic field, and I was pointing out that the initial concept was more correct.

Jon
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Laminations, thin sheet of metal are to help manage the eddy currents in the intended magnetic path.
Slots, air gaps, in sheet metal are to minimize or redirect the currents from an unintended magnetic path. These two results are not related, other than they deal with induced currents.
 
How about this. Cut the steel deck away from the area the cables pass through and replace it with concrete reenforced with this

ocpb.jpg

Owens Corning "Pink Bar"

It's a fiberglass product
 
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