wire twisting

[erosroberts]

I was watching another electrician install and wire a inverter and while wiring it he twisted the DC+ and DC- conductors befor terminating them. Does anyone know why ?

 

[ERIC LEDBETTER]

Maybe so all the strand will fit under the screw

 

[texie]

I was watching another electrician install and wire a inverter and while wiring it he twisted the DC+ and DC- conductors befor terminating them. Does anyone know why ?

I think you are saying that the conductors were twisted together to make a twisted pair. For DC I can't think of a technical reason. I have seen this done for cosmetic purposes though.

 

[BillK-AZ]

Twisting and lacing to protect DC cables.

Twisting and lacing to protect DC cables.

In a high current fault condition, the conductors repel (push apart) due to the magnetic fields around each conductor. This rapid increase in the distance between the wires can pull the wire out of the terminations.

Twisting and lacing protects the cables from this. They can not easily pull apart.

I once saw a situation where unlaced parallel cables that were placed in a trough in the floor and covered by a board (in Africa) really caused a problem. These were cables from a 240 VDC battery bank to a large inverter. When the switch was closed to energize the system for the first time, the capacitors in the inverter caused an immediate high current as they charged and this surge caused the heavy (about 500 mcm) cables to repel, sending the boards flying, pulled the cable out of the inverter, and the dancing cable caused several burns as it welded to various metal items. You would not want to be near that. The plans called for lacing, but the importance of lacing was not recognized by the local installers.

The communications industry that has a lot of DC runs, requires lacing of all DC power cables to prevent this situation.

 

[mlnk]

How do you do lacing?

 

[fmtjfw]

How do you do lacing?

http://en.wikipedia.org/wiki/Cable_lacing

 

[Smart $]

How do you do lacing?

http://www.tecratools.com/pages/tecalert/cable_lacing.html

[URL]https://www.google.com/search?q="cable+lacing"&hl=en&prmd=imvns&source=lnms&tbm=isch&sa=X&ei=sBQ6UJ7zNu7G0AH6koFQ&ved=0CAoQ_AUoAQ&biw=1078&bih=1071

[/URL]

 

[S'mise]

Think hes talking about twisting the wires like braiding, Not lacing. Twisting DC wiring is often done to avoid inducing AC interferance on the DC circuit. This "noise" can interfere with electronic signaling. A good practice, especially at termination points.

 

[Smart $]

Think hes talking about twisting the wires like braiding, Not lacing. Twisting DC wiring is often done to avoid inducing AC interferance on the DC circuit. This "noise" can interfere with electronic signaling. A good practice, especially at termination points.

The OP is talking about twisting... but I doubt it's to reduce EMI... it's regarding power DC conductors to a DC-to-AC inverter... not low voltage communications circuits. Lacing came up because of the reason for twisting.