Installing 600V single conductors in cable trays

[gdeep]

Hi,

This has been a very good learning forum and I hope to learn a lot from you guys. Thus my first post & the question

I am installing 4 X single conductor 600V 750MCM teck cables in a cable tray( hot dipped galvanized steel) which would be bonded at every 15m. These cables would be installed at free air rating( cable diameter apart). I have heard about eddy currents being a problem where single conductors are involved and heard about using non ferrous clamps and terminations for such cables. My question is if the eddy currents can cause heating up of the cable trays in which these cables are getting installed. Pls correct me if I am wrong.

Any help would be appreciated. Thanks

 

[waross]

The heating occurs when a magnetic path encircles a conductor. For single conductors the straps or clamps should be non-ferrous. An exception may be if one-hole straps are used which do not form a complete magnetic path. ie: There is a small gap between the end of the strap and the cable tray.
Beware of your terminations. The connectors and lock nuts should be non-ferrous. I have seen inspectors call steel lock-nuts on the cable connectors and demand that they be changed to non-ferrous.
Heating will occur in ferrous cable clamps and in the part of the ferrous tray which completes the magnetic encirclement below the clamp.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[gdeep]

Thanks for the response.

Just so that I am clear, can the cables cause a heating effect on the rungs( 12 inch apart) of a ladder cable tray( 24 inch width). Should this be of concern. I have noted about non ferrous terminations & clamps and have specified it to the electrical contractor.

 

[waross]

Not unless ferrous P-clamps or ferrous two-hole straps are used. Aluminum straps are available.
There may not be much heating below about 200 Amps per conductor.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[gdeep]

Thank you

 

[moreause]

don't forget with single conductor teck cable
you have to connect the ground only on the feed side (by standard)
the teck connector have to pass thru a non ferrus material...aka aluminium or stainless

and at the other end the connector must pass thru a fiber plate

that is to prevent current to floe into the teck armor