Cable Ampacity

[McCES]

I have a drive isolation transformer at 1400V. The drive manufacturer spec calls for 8kv cable from the xfmr to the drive package (to withstand spiking). The cable needs to carry 600A.

The question is: since the system voltage is less than 2000V do I use the conductor ampacity ratings in table 310.16 for cable up to 2000V or do I use the ampacity rating of 5001-35000V cable from table 310.69?

 

[StephenSDH]

Is it a regenerative system? Sounds odd to install cables for 6x the system voltage. If it has spikes like that I hope the transformer does its job of isolating the spikes.

I'd say you need to use the ampacity column for the type of wire you are using. I doubt your medium voltage cable type is listed in the top of 310.16 columns. The wire's insulation type determines the wires ability to withstand heat and dissipate heat. The top of 316 says "Insulated Conductors Rated 0 to 2000 Volts" instead of system voltages 0 - 2000 volts.

Good luck

 

[McCES]

Thanks Stephen.

That's the conclusion we came up with as well.

Thanks again.