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| Convertable Distro [message #323570] |
Fri, 16 May 2008 20:51  |
 trace knight
Messages: 265
Registered: April 2004
Location: Akron, oh. |
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I need to build a distro that can convert from 3 phase to single phase, and still keep the loads somewhat balanced. I have a job coming up, where they only have a single phase incoming service, it breaks to a 400 amp disconnect, and I have 3 phase distro's for the rig I'm using. I know I can just t tap the last leg, but that really is going to set off an imbalance like to the tune of over 160 amps differential.
I don't really think this is the wisest in this case. I was thinking I once saw a 4 bus (3rd was a 2 part) main panel, where the z and y were normal, and the z had 2 bus hots tied together like z-a and z-b, when used in the 3 phase, it was like z/y/z-a+z-b. When used in single phase it was configured like x+z-a and the other leg was y+z-b. Confused, I'm not, just not sure how to go about this, other than cutting the 3rd bus rail, then coupling them together using a large capacity switch or contactor. (key locked of course). Any ideas, or am I over thinking this. I don't use 220volt for anything, so it's just a matter of doing the third leg swap.
tk
[Updated on: Fri, 16 May 2008 20:54]
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| Re: Convertable Distro [message #323592 is a reply to message #323570 ] |
Sat, 17 May 2008 00:02  |
Kevin Windrem
Messages: 73
Registered: March 2007 |
Should Get Out More |
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| trace knight wrote on Fri, 16 May 2008 20:51 |
I need to build a distro that can convert from 3 phase to single phase, and still keep the loads somewhat balanced. ...
tk
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I've thought about this too. There's little 3-phase power in my area so I end up using only two lets when I do find a 3-phase source. Many lighting racks have the internal routing to split the third leg in half and connect each half to the first half. But breaker panels are simply not set up for it. There's no way you could safely cut a bus bar. You really need 6 buses to do the rerouting to avoid any 2-phase branch circuits ending up on the same phase.
Of course if you have any 3-phase branch circuits (e.g., L21-30) there's no configuration that would be legal short of feeding two of the legs in the branch off the SAME BREAKER.
The most straightforward solution would to build separate 3-phase and single phase distros.
You could also construct three smaller single phase distros and interconnect the inlets based on the supply:
Single phase 3-phase
Box 1 X In X X
Box 1 Y In Y Y
Box 2 X In X Z
Box 2 Y In Y X
Box 3 X In X Y
Box 3 Y In Y Z
[Edit to clean up "table"]
[Updated on: Sat, 17 May 2008 10:16]
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| Re: Convertable Distro [message #323682 is a reply to message #323649 ] |
Sat, 17 May 2008 12:23 |
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Mike Pyle
Messages: 1666
Registered: April 2004
Location: Napa, CA |
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| Thomas Mikarlsen wrote on Sat, 17 May 2008 07:40 |
A good solution is to have a harting 6 or 12 pole input, and make two sets of supply cables.
We use it a lot to change between 400V star 3-phase and 230V delta. 3-phase. Can easily be converted to work for single phase/ 3-phase switching.
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Can you post a link to that connector? That's the way I've been thinking of going but I'm not familiar with acceptable high current multipole connectors.
Mike Pyle
Audiopyle Sound
Dealer for Yorkville, Allen & Heath, APB Dynasonics, QSC, RCF, KV2, FBT, JTR, Danley,
Audix, SLS Audio, Genie, RoadReady, K&M, Ultimate, Global Truss, DENON, Elation...
707-315-6204
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| Re: Convertable Distro [message #323848 is a reply to message #323570 ] |
Sun, 18 May 2008 10:29 |
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Lee Patzius
Messages: 1451
Registered: April 2004
Location: St. Louis MO |
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Here's an example of how you could hook in an ASCO Model 165 Manually Operated Transfer Switch, as a single-to-three phase switcher.
The top drawing (red X'd out) is the original, intended for generator transfers.
The bottom drawing is a modified version (I threw together quickly) for phase switching.
EDIT: It would be ideal for use with two 2-pole single phase panels instead of cutting a 3-phase panel's z phase bus in half (and backfeeding it through a breaker).
[Updated on: Sun, 18 May 2008 10:47]
Lee Patzius
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| Re: Convertable Distro [message #323910 is a reply to message #323848 ] |
Sun, 18 May 2008 18:27 |
trace knight
Messages: 265
Registered: April 2004
Location: Akron, oh. |
Has No Life |
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I'm not seeing any good means of keeping the loads balanced, without spending a ton of money,so I guess, I'll just build another distro, and deal with it that way. I have a huge supply of parts, so it'll be just a matter of time. I could have sworn I saw something at another time and place, but alas, like the rest of the world good ideas, if it's not gonna sell millions, is more than likely in the shitter now.
tk
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| Re: Convertable Distro [message #323963 is a reply to message #323570 ] |
Sun, 18 May 2008 22:44 |
Geri O'Neil
Messages: 2083
Registered: April 2004
Location: Bottom of someone's shoe |
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Trace, here in the Armpit of Civilization, we still see a lot of single-phase power. Hell, we can't even get 3-phase to our new shop, when it's finished.
I've gone over this and over this for years now and I've just about given up on a convertible solution. We're just gonna build two different PDs for use in the respective situations, as you've about decided to do. I still want to see the Motion Labs set-up with their switcher, but I believe that they won't sell the switcher with L21-30 outlets, only L14-30 outlets due to the imbalance possibilities. Which would be fine with me, that's how our racks are set up now anyway. The cost is out there, but it's in the running
Of course, you could build your switching system with double-neutrals like we're seeing done with some larger lighting rigs these days. Like copper is cheap these days. Funny, I don't see the lampies sweating this situation too much. It is possible, if coincidental, to come up with a lighting scene that puts nearly all of the load on two legs in 3-phase or 1 leg in single-phase. Ouch.
Geri O
[Updated on: Sun, 18 May 2008 22:47]
"Stagelite Sound...A Pin 2 hot-compliant company"
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| Re: Convertable Distro [message #323973 is a reply to message #323960 ] |
Sun, 18 May 2008 23:32 |
Tim McCulloch
Messages: 3819
Registered: April 2004
Location: Wichita KS USA |
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| Kevin Windrem wrote on Sun, 18 May 2008 22:35 |
| Tim McCulloch wrote on Sun, 18 May 2008 18:50 |
Hi Trace-
I think the way to go is to wire your amp racks (and FOH, utility, etc) and distro for 3 phase with L21-30s or whatever connector works best with your loads.
Buy/build the "split Z leg" 3-to-Single phase switch. You're all set. If you go all 3 phase later, just remove the switchgear and lug the split Z together.
Let us know what you finally do and how you went about it.
Tim Mc
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You can't run L21-30s off of two phases/legs. Regardless of how you wire it, two legs of the L21-30 would end up on one "phase". That would overload the neutral!!
If you need to run your system off of single phase (120/240), all branch circuits need to be a maximum of two legs (L14-30s). You when you wire up the box, you need to make sure that any two-legged branch never ends up with both legs on the same circuit.
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Commercial versions of these get UL and other listing agency approval. I doubt they would be offered if there was something inherently unsafe *when used as directed*.
Yes, there will be neutral imbalance, and therefore incumbent on the builder and *user* to over-size the conductor accordingly.
I don't for minute suggest this as a DIY project, or for those who don't understand the implications of what this does.
Tim Mc
"It's not your fault if he can't play the part. Let him suck out loud."
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| Re: Convertable Distro [message #324273 is a reply to message #323963 ] |
Mon, 19 May 2008 22:06 |
HarryBrillJr.
Messages: 698
Registered: April 2007 |
Has No Life |
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Geri,
Good to see you here!
The L21-30 is a 3 phase connector. The load potentially place on the neutral could be double if you had it wired X Y Y and had nothing on the X leg. This is the main reason they won't connect the Z terminal of the L21-30 to the single phase side of the switch. When I was dealing with this, they were still willing to sell us the distro configured with both, but wanted to make sure I understood the Z leg would not work on the L21s when using single phase power. A re patch in the amp racks would take care of that problem. If you are stuck with single phase power, chances are you don't need to drive the rig full tilt. Your area may be different. I haven't tied into single phase in years.
Harry Brill Jr.
http://www.geocities.com/proaudioguy/
http://www.rationalacoustics.com/
http://www.rationalacoustics.com/forums/
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