Power Cable Configuration

[jam]

I am reading through a spec that requires 3 phase power cables run in a cable tray with control wiring to be 6" away or to cross at 90 degrees. I guess so that the power cables do not to induce noise into the control wires.

But why are they required to be bundled in a specific configuration. The spec calls for triangular bundles for 3 wire, and square for 4 wire.

Any idea what the theory is here ?

Thanks.

 

[jtester]

Re: Power Cable Configuration

The requirement for bundling will reduce the circuit impedance and improve overall operation. That said, the reduction is minimal. Impedance of a circuit is based on conductor spacing as well as other factors. Bundled conductors will be closer together than randomly laid cables, and will present a lesser impedance. I believe that the spacing factor in a cable tray is insignificant, except in extreme cases.
Jim T