Sorta OT: Power Distribution

[TimothyMoulder]

Not PLC related, but electrical safety nonetheless. Don't wanna fry my maintenance men

We have a project employing 3 robots, each with 480 VAC 3-phase power. We also have 6 welders, each with 230 VAC single-phase. Last but not least, we have the rest of the controls, with 230 VAC single phase that we'd like to keep seperate from the welders.

With so many draws, I am unsure how to distribute the power from my main panel and still maintain safety. For instance, I could take the easy way out and drop a power line to each component. But then, if I lock out my control panel, my welders and robots still have energy - not safe.

Unsure how to proceed. Any suggestions?

Thanks!

TM

 

[rsdoran]

The simple thing would be to sub-feed the 230vac from the 480vac provided to the control panel i.e. if control panel is off they will be too.

If you want to feed the power separate from a main panel you can place the main breakers for all the feeds in your control panel with disconnects on the door i.e. all 3 disconnects will need to be off to open the door.

Last but not least you could "interlock" the 230vac supplies through a contactor or externally trippable breaker that will disengage if/when the control panel is turned off.

Just a few thoughts.

 

[TConnolly]

The simple thing would be to sub-feed the 230vac from the 480vac provided to the control panel i.e. if control panel is off they will be too.

Without knowing more about the actual system, thats the option that would be my first choice. Transformers are cheap.

 

[TimothyMoulder]

Thanks for the suggestions, guys.

The power requirements for all those welders will use alot of transformers, not cheap in volume, and bulky to boot.

I like Ron's "last but not least" suggestion best, use a 480 VAC coil contactor to switch the 230 VAC from a separate drop. My only concern in this is - what if the contacts fuse? Or am I being overly cautious?

 

[TConnolly]

Then use redundant safety contactors with guided contacts and a safety monitoring relay. This can all be integrated into your estop string with seperate contactors for the 480 and 230 V systems. When either the 480 or 230 disconnects are off, interrupt the estop string.

Its up to you though to make sure that lockout tagout can still be accomplished.

 

[rsdoran]

My only concern in this is - what if the contacts fuse? Or am I being overly cautious?

I do not think you can be overly cautions anymore. I would also have stated use safety monitoring relays.

 

[Gerry M]

The power requirements for all those welders will use alot of transformers, not cheap in volume, and bulky to boot.

Unless space is a problem, Price it out both ways. Like Alaric said Transformers are cheap compared to some of the extra wiring the other option will involve.

 

[TimothyMoulder]

Found it!

The critter I need is by Bussman, part # BDZW2. This is a mechanical device that allows two disconnects to be actuated and locked out via a single handle. They call it a "conversion mechanism".

Now I just gotta find a vendor to sell me one!

Link: http://www.bussmann.com/library/docs/Disconnect/60-100Afds.pdf

It's on the last page of the PDF.

Thanks for the suggestions!

TM