single phase dimmer rack from 2 legs of a 3p4w delta pan

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collier

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i church project i am working on just purchased a Lightronics dimmer #AR-1202. the instructions make the following statement.

to operate the AR-1202 on 120/240 single phase power...i am quoting

"the unit should be run on 2 hot legs which are NOT the same phase. the 2 hot legs must be actual single phase power. this means that the two input power hot legs must have a 180 degree electrical phase offset from each other. THE UNIT WILL NOT OPERATE IN A SINGLE PHASE CONFIGURATION FROM 2 LEGS OF A 3 PHASE SUPPLY CIRCUIT"

does this make any sense? obviously i will not be using the "high/stinger" leg. i have talked to 2 engineers and they can't understand why it will not work if i have 240 volts between each phase and 120 volts to ground from each phase.

the 180 degrees is what i am not sure of

thanks
 
Re: single phase dimmer rack from 2 legs of a 3p4w delta pan

I don't know if it makes sense or not but if I had a piece of equipment that specifically stated in the instructions "THE UNIT WILL NOT OPERATE IN A SINGLE PHASE CONFIGURATION FROM 2 LEGS OF A 3 PHASE SUPPLY CIRCUIT" I would not even consider trying to connect it to a 3 phase system

I would tell the customer they need to buy a transformer to create 240/120 single phase or they need to get a different dimmer unit.
 
Re: single phase dimmer rack from 2 legs of a 3p4w delta pan

Originally posted by collier:The unit will not operate in a single phase configuration from 2 legs of a 3 phase supply circuit.
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That makes perfect sense. On a 120/240 volt system, if you get power from two poles of different phases, you will get 240 volts between the two wires. That is what the manufacturer wants. But on a 120/208 volt 3-phase system, if you get power from two poles of different phases, you will get 208 volts between the two wires. The manufacturer is telling you the equipment cannot operate at 208 volts.
The 180 degrees is what I am not sure of
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This is the standard configuration of a 120/240 volt, single phase, 3-wire system, even if we do not often use the term "180 degrees" to describe it.

You get such a system by taking a single phase secondary with 240 volts from end to end, and connecting the "grounded" wire to the center point. That means that the voltage will increase (as you pass through the secondary winding) from one end to the middle, and continue to increase from the middle to the other end. But the center point is connected to planet Earth. So if you look from the center towards the two ends, the voltage gets lower as you go from the center to one end, and the voltage gets higher as you go from the center to the other end. The voltages measured at the two ends are opposite from each other. One is positive with respect to the center, and the other is negative with respect to the center. That is what is meant by being 180 degrees out of phase.

Does this help clear up the confusion?
 
Re: single phase dimmer rack from 2 legs of a 3p4w delta pan

Originally posted by iwire:I would tell the customer they need to buy a transformer to create 240/120 single phase or they need to get a different dimmer unit.
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I think this might be the right thing to do. It seems that the equipment they bought is not compatible with their power supply panel.

However, I am not familiar with the 3-phase delta with a "high/stinger" that you described. If you really can get 240 volt single phase from that transformer, then it should work. All the manufacturer wants is that you not use 208 volts, which you would get with a WYE connected, 120/208 transformer.

{Edit: I had to go back and rethink, then re-state my comments, based on the type of transformer you have.}

[ July 15, 2005, 06:53 PM: Message edited by: charlie b ]
 
Re: single phase dimmer rack from 2 legs of a 3p4w delta pan

collier
I would call the factory as the 3-phase they were refering to is a 120/208 "Y" service
the two legs (B,C) of a 4-wire 120/240 volt service is in fact 180?s out of phase with each other. these two legs are infact derived from a single phase transformer with a center tap. I have installed a few NSL units that had this same restriction with no problems as long as the "B" phase was not used. I called NSL (which is owned by Leviton now and they said that this would not be a problem. You can use these units on a 120/208 service but you have to use all three phases.

Here is link to their web page and the spects for this unit:

AR-1202

[ July 15, 2005, 07:07 PM: Message edited by: hurk27 ]
 
Re: single phase dimmer rack from 2 legs of a 3p4w delta pan

Wayne Maybe I am just a paranoid person I would not ignore instructions like that just on a phone call.

All I would be thinking is If smoke comes out now or in the future we own it. :(

Bob
 
Re: single phase dimmer rack from 2 legs of a 3p4w delta pan

thanks for the responses. my question is do you think the dimmer will work?

1. the dimmer panel will be fed from what i call a 120/240 volt delta 3 phase 4 wire panel
2. the voltage between legs A&B, A&C, and B&C =240
3. With Neutral(N), the voltage between A&N=208,
B&N=120, and C&N=120
4. the panel is being feed from an overhead utility bank of what appears to be 3 single phase transformers

the company making the dimmer has responded saying with those voltages it will work, but that seems to me to be directly opposite of the instructions.

it seems to be i am deriving a single phase 120/240 system from 2 legs of a 3 phase sytem.

since i will be energizing this panel next week, i want to be sure

note: the dimmer panel has 12 120 volt circuits/channels. the instructions say it will operate off 120/208 3ph 4wire, or 120/240 single phase.

i don't want to spend $1000 on a dry transformer to try and convert my voltage to true 180 degree 120/240 single phase (whatever that really means), if i already have it

thanks - collier
 
Re: single phase dimmer rack from 2 legs of a 3p4w delta pan

I agree Bob but I had spoken with the engineer who did the script for those instructions and they were changed in the next units. But there was one flaw I forgot about and that is the restriction on the un balanced loads on an open delta transformers, These units require 120 amps when fully loaded as most are. The Color Tran I install in one club would start oscillating when loading would get to high and this would do this on the whole service so everything in the building received this strobe effect in voltage fluctuation. Not good! The power company installed another transformer to stop it and closed the delta. Which allowed higher levels of un-balance loads but there still was a limit but I think it was somewhere around 57% which we never exceeded. before the limit was more like 5% with the open delta. :D
The way the instructions are worded is the supply has to have 120/240 volts that is provided with an phase angle of 180?. A 4-wire delta does provide this between phase "A" and "C" as you are only connecting to the one transformer with the X0 tap, There is nothing that a stand alone single transformer would be different from. I was told one of the reasons that this requirement was put into the instructions was the engineer had never heard about a 4-wire delta and didn't know about them so he assumed that the only 3? service was either a straight 3-wire delta or A 4-wire "Y", What I was told was the delta couldn't be used because of the lack of a neutral to produce a circuit balance for 120 volt lamp loads, and the 120/208 "Y" couldn't be used because of the 60? phase angle would not allow full range dimming. (Not to sure why it works with all 3 phases but it does ;)
 
Re: single phase dimmer rack from 2 legs of a 3p4w delta pan

Coller just to confirm the phase I mention I noticed that your "A" phase is your high leg, which it is normally "B" phase, so in your case you would want to connect to just the "B" and "C" phases in your panel. And since you have 3 transformers the un-balance loading is not as much of a problem. If you are concerned about the warranty then see if the manufacture will send you an up dated instruction book to reflect these changes.

[ July 15, 2005, 08:39 PM: Message edited by: hurk27 ]
 
Re: single phase dimmer rack from 2 legs of a 3p4w delta pan

Collier
Call the factory and tell them want you have for power. Your power you have will work. I've used these type of power packs before. You can interlock several together. I belive that your only using 120 volt per pack but if you have several they want to split to power up some. Some power packs will handle between 1800 watts to 2400 watts so you can see want they are wanting. I use to play in a rock band many of years ago and we ran each pack to it's max. But you needed the power for them. We had to deal with single phase 120/240 power at most places. A 100 service we had to use just because of the lighting. Now when we set up the whole system we put all the lights on A phase and all the power for the rest of the equipment was on B phase. Tried to balance as close as we could. The reason why we did it this way is so we didn't have any buzzing from the lights. Dimmer packs will do that unless you have a lot of money to buy the filters. Sorry I wrote so much but it was a good time for me. Had a lot of fun.
Jim
 
Re: single phase dimmer rack from 2 legs of a 3p4w delta pan

Jim look at the (AR1202) link in my first post and you will see that these are indeed a all in one unit that has 12 channels @ 2400 watts for a total of 28800 watts which is far greater than the packs your talking about. the instructions allow for 120/240 1?, 120/208 3? "Y" as for power supply but doesn't mention a 4-wire delta (120/240 3?) service. the unit requires a 120 amp circuit when feed with 120/240 1?

The club I mention about the Color Tran dimmer pack was also a All in one unit but had a 4800 watt per channel rating but with only 6 channels.
 
Re: single phase dimmer rack from 2 legs of a 3p4w delta pan

hurk27
Should have looked over your writing a little closer. Will pay more attention next time.
Thanks!
Jim
 
Re: single phase dimmer rack from 2 legs of a 3p4w delta pan

The following is the description of the AR-1202 from the Lightronics web site:

The AR-1202 is a 12 channel x 2400 watts per channel dimmer. It accepts DMX-512 signals and allows remote station control of preset scenes.

The unit operates from either single or three phase power.

The highly versatile AR-1202 may utilize multiple remote stations to activate specific user programmed scenes pre-stored in the unit. Several remote types may be used. The unit is listed to UL-508 requirements.

If you have to specify the power source when you buy the unit, you may have specified the wrong power source.
 
Re: single phase dimmer rack from 2 legs of a 3p4w delta pan

The 240/120 3? 4Wire System, described by the original poster, should be OK - as the "Lower" end of the Delta is simply a 1? 3Wire System - derived from a 1? Pot (Transformer), with the Secondary Coils connected in Series Adding, and a "Tap" from the "X2-X3" Jumper points for the System's "Neutral".

In all aspects, this is a Single Phase System, with an optional Three Phase ability.

It sounds funky, but look at the application of the 4 wire delta - for use where the majority of the loads are single phase, and with the ability to drive limited polyphase loads.
Otherwise, there would be a 3 wire delta - either grounded or ungrounded, and the Customer would be responsible for obtaining L-N load power via Separately Derived System(s).

Just my 2?!

Scott
 
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