db/cu and 521.5.1 Ferromagnetic enclosures: electromagnetic effects

Thanks for the tip about the demo using the buzz box welder and the conduit - it is pretty obvious after it has been mentioned, but I had not thought of it as a way to show the effect and explain why wires in steel conduit ought to balance flow and return.  That's this afternoon's activity  sorted then.  I now suggest that that one could also do an all cores in parallel version of the welder test with some steel wire armoured cable - like the conduit there should be a discernable effect, but the armour being wires with some in contact and some gaps, rather than a solid magnetic cylinder, confuses matters, if anything making the magnetic coupling effects weaker.

It is very telling that on the welder  the two wires come out of two separate holes in the steel plate, and while the front panel, well the whole thing actually, does look rather like a bomb has hit, there is no evidence of any extra heating around the wire exits.

Mike..

Thanks for the tip about the demo using the buzz box welder and the conduit - it is pretty obvious after it has been mentioned, but I had not thought of it as a way to show the effect and explain why wires in steel conduit ought to balance flow and return.  That's this afternoon's activity  sorted then.  I now suggest that that one could also do an all cores in parallel version of the welder test with some steel wire armoured cable - like the conduit there should be a discernable effect, but the armour being wires with some in contact and some gaps, rather than a solid magnetic cylinder, confuses matters, if anything making the magnetic coupling effects weaker.

It is very telling that on the welder  the two wires come out of two separate holes in the steel plate, and while the front panel, well the whole thing actually, does look rather like a bomb has hit, there is no evidence of any extra heating around the wire exits.

Mike..