Conductors in Parallel and Division of Current
Conductors in Parallel and Division of Current
(OP)
I am planning on running two sets of four single core #4/0 conductors in parallel PVC conduits. The raceways and conductors will be identical in size and length. Since the individual conductors will be pulled through each raceway, the conductor orientation and hence reactance may be slightly different in each set of conductors.
The Canadian Electrical Code states the following:
"The orientation of single-conductor cables in parallel, with respect to each other and to those in other phases, shall be such as to minimize the difference in inductive reactance and the unequal division of current."
Is it possible to achieve this requirement using conduit as a raceway?
The Canadian Electrical Code states the following:
"The orientation of single-conductor cables in parallel, with respect to each other and to those in other phases, shall be such as to minimize the difference in inductive reactance and the unequal division of current."
Is it possible to achieve this requirement using conduit as a raceway?






RE: Conductors in Parallel and Division of Current
In conduit, if the cables are installed in a straightforward manner by a competent crew, they will naturally take a configuration that minimizes reactance. The presence of full size neutral conductors may have a slight effect, when neutrals are smaller than the phase conductors they often are squeezed out of the trefoil bundle and the bundle cancels well.
BUT, construction crews don't usually worry about reactance in conduits. The close spacing gives good cancellation even when the physical arrangement is not perfect.
An experienced crew using cables that are straight will often feed the three phase conductors into the conduit in a trefoil configuration with the smaller neutral fed in beside the bundle. There will be some flattening of the trefoil in the bends but mostly the configuration will stay somewhat trefoil. The smaller neutral conductor often does not enter the bundle.
With a same size neutral, there will be some mixing but it never seems to be an issue in the field.
Bill
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"Why not the best?"
Jimmy Carter
RE: Conductors in Parallel and Division of Current
Do you think there is value in testing the current division between the two sets during commissioning of the plant?
RE: Conductors in Parallel and Division of Current
Also weigh the possible danger in making hot measurements against the value of the information.
RE: Conductors in Parallel and Division of Current
As for testing, the quality of the connections may be more important. I may check the connection temperature with an IR spot meter. A connection that is running unexplainably hotter than the others may be a sign of future trouble.
How much hotter is a matter of judgment and experience.
Bill
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"Why not the best?"
Jimmy Carter