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# Magnetic field in steel framework

## Magnetic field in steel framework

(OP)
We have a planar steel framework made of rectangular tube steel members.  There is a long straight conductor running through and perpendicular to the plane of the framework carrying 2000 amps. We have a B/H curve for common low carbon steel.
Questions:  1) Is the magnetic field intensity at any point along a given RADIUS constant or does it get reduced by the steel members closer to the source? (See attached sketch.)

### RE: Magnetic field in steel framework

The steel members will absorb and re-direct the flux lines.  It will not be constant along a given radius.

### RE: Magnetic field in steel framework

(OP)
What is best way to determine the heat input into the steel? Do you sum the volumne of steel for the entire wall?  What equation would I use to determine the flux density or directly watts/lb of steel?

### RE: Magnetic field in steel framework

Is the current AC or DC?

### RE: Magnetic field in steel framework

I'd be concerned that the AC current would induce currents in the framing, which could potentially cause electrolytic reactions.

### RE: Magnetic field in steel framework

(OP)
AC current.  The steel will be galvanized.

### RE: Magnetic field in steel framework

jt83: Your situation is more complex than it appears.  I'm pretty certain you'll have to use finite element analysis (or find a consultant who can do FEA) to get an answer.

It's possible someone has developed a general equation to describe your situation, but I am not familiar with it.

### RE: Magnetic field in steel framework

jt83:

Assuming that you are dealing with an isolated bus pentrating a bulk-head of some sort (unable to view your scketch), you start by estimating the field produced by the buss wiring at the metal frame location. you can then estimate the induced current in the steel work and determine if saturation is occurring.

at a minimum the bulk head penetration adds a bit of impedence to the circuit and creates localized heating especially if you provide a closed path cor the induced currents.

seems like a lot of work was done on this in the early 1930's when poly phase power became popular and led to buss duct installations rather than each buss being run separately.

quite a few papers written on the subject where cylindrical penetrations were studied

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