resistance in circuit
resistance in circuit
(OP)
Hi, I installed light fixtures in a large facility using a pre-fabricated cabling system consisting of mc cableand plugs at each fixture.
The cables come in standard lengths, which was about 5 feet too long for the span I'm crossing, so I coiled and wire-tied them above each fixture (2 loops). I now have 14 of these windings; what I'm worrying about is this:
Am I creating any neglible resistance?
And will there be any neglible inductance?
I'm running 480/277 volt multi-wire circuits,.83amps/fixture @277v in 12 ga. wires.
The cables come in standard lengths, which was about 5 feet too long for the span I'm crossing, so I coiled and wire-tied them above each fixture (2 loops). I now have 14 of these windings; what I'm worrying about is this:
Am I creating any neglible resistance?
And will there be any neglible inductance?
I'm running 480/277 volt multi-wire circuits,.83amps/fixture @277v in 12 ga. wires.





RE: resistance in circuit
The induction is negligible and what there is is self cancelling.
The 14 x 5' = 70 feet of cable is not a problem by itself, but you may want to check the voltage drop tables to determine the maximum footage allowable for your circuit configuration.
yours
RE: resistance in circuit
I did calculate the voltage drop, and am getting under 1 percent VD.
Can you explain how the induction cancels itself?
RE: resistance in circuit
No net induction. No problem.
yours
RE: resistance in circuit
just curious
respectfully
RE: resistance in circuit
A cable is in practice a bifilar winding. And as such not having any inductivity. At least not one that increases when the cable is coiled up.
Gunnar Englund
www.gke.org
RE: resistance in circuit
Maybe I didn't make myself clear enough; my circuit consists of 2 (hot) wires and 1 grounded (neutral) wire.
In a perfect world the 2 hot wires will carry all of the current, and the neutral wire none at all. This would be 2 circuits flowing in the same direction, and thus amplifying the inductive current.
Being this is not a perfect world, I imagine the neutral wire will have to carry any unbalanced portion that may exist. This is what would (would!!) cancel the inductive current.
Am I right here?
I copied the following out of an encyclopedia
Some bifilars have adjacent coils in which the convolutions are arranged so that the potential difference is magnified (eg., the current flows in same parallel direction). The magnetic field created by one winding is multiplied with that created by the other, resulting in a greater net magnetic field.
Others are wound so that the current flows in opposite directions. The magnetic field created by one winding is
therefore equal and opposite to that created by the other, resulting in a net magnetic field of zero (eg., neutralizing any negative effects in the coil). In electrical terms, this means that the self-inductance of the coil is zero.
respectfully,
RE: resistance in circuit
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: resistance in circuit
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I don't suffer from insanity. I enjoy it...
RE: resistance in circuit
If the current in the hot wires is not equal, the difference will flow in the neutral in such a direction as to cancel.
yours