Power drops to control panel question...

[James Fillmore]

We are building a line of standardized machines; servo driven press, high power IR lamp, plastic assembly machines. A stand alone machine.

I'm thinking of creating a servo / plc enclosure and then a power enclosure. Reason is the servo / plc panel would be very standard but the power panel could be anything from a few kw of phase angle power control to hundreds of kw.

The plc / servo panel would require about 30A of 480VAC. The IR power panel would require 60A to over 600A of 480VAC. Out of convenience for the customer it'd be nice to have one 480VAC drop and then quick connect the PLC panel to the IR power panel. Only connections between the 2 would be 480VAC power for the servo equipment and power supplies. And a couple dozen digital and analog control wires from the PLC to the power controllers and contactors.

Bottomline, SHOULD I have (2) 480VAC power drops? If I did the only wiring between the 2 control panels would be low voltage.

If I had (1) drop on the IR power panel I'd have to run 480V to the plc / servo panel. Would probably have to feed the top of a disconnect on the plc / servo panel. Would be nice if this was or could be made a quick disconnect cable to the IR power panel.

Anyone done something similar? Any suggestions?

TIA

[TConnolly]

Its done all the time. We do something similar on our large hydraulic presses. We run the main 480V drop to one panel. In that panel we route through a smaller breaker, then take 480V to the second panel. The second panel also has a disconnect/breaker.

Since your power is leaving the first cabinet make sure you use a breaker rated for branch circuit protection and not a supplemental protection breaker. Because its 480V, plan on a disconnect and door interlock at the second panel as well as the first.

It goes without saying, adhere to NEC rules.

[James Fillmore]

Do you hard pipe/wire the 2 together or quick disconnect them?

Do you just label "power fed from another source" or something or do you use yellow or yellow striped black wire to run the 480V from the power panel to the PLC panel?

Yep, I'd have a small disconnect on the plc / servo panel.

Thanks for the info!

[jraef]

For only 30A I would do it with multi-pin connectors. I like Brad Harrison / Woodhead (now part of Molex). They have a power connector called Brad Power and then use the regular Brad/Woodhead Minichange connectors for the control circuits. You can key the control connectors so that they cannot be plugged in the wrong sockets.

[TConnolly]

We hard pipe them together. The panels are labeled for power source. Also the second panel disconnect is labeled to indicate that it only shuts off a portion of the machinery.

[nwboson]

I'm in the same camp as Alaric: you can't beat hard wiring for reliability.

Don't forget to think about your neutral conductors, earthing requirements, and how you're going to avoid any ground loops.

It is common practice to run all your power into one panel then distribute out from there with separately fused (breakered) branch circuits. This also gives you the opportunity to properly label your FLA for your entire system.

Do your earthing in just that one panel, run your current carrying neutrals so they all only get their earth reference at only that one location. Ground loops can make your PLC circuits a nightmare!

[tracer]

with all the arc flash stuff, it's becoming more common to have your high voltage in one cabinet, and the plc and low voltge components in another...