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I just reviewed the draft site requirements for digital conversion. One of the requirements was for a 3-phase 208V, 60 amp (per leg) circuit. Since I currently have 3-phase 240V power coming in, that condition would require a several thousand dollar conversion. Around here anyway, 208 isn't common. Why would that be a requirement?

I sure hope those 3 phase requirements aren't set in stone. If so, I'll be kicking myself when the time comes.

In my case it's highly ironic because part of the ongoing renovation on my theater has been to completely rewire the place. I had an engineer look at the wiring and tell me that I only had single phase power. Others told me that there was no 3 phase power in the area. The power supply in the old booth was single phase. So, the engineer drew up plans that only called for single phase rewiring. After the demolition of the old wiring system and half-way through installing the new wiring the electrician mentioned to me that the old wiring had been 3 phase, and I think 208 volt. I already had purchased some single phase equipment and already made plans to buy more, so I let it go. Now, I get this news. I guess I should have been checking on requirements for down the road, but I didn't.

The only possible consolation would be that somebody would be able to assure me that digital equipment could be adjusted to accept single phase power, or for the benefit of Burney, alternate forms of 3 phase power.

Anyone?

The 3-phase would be for the lamphouse power supply. Most of those can handle 240. I would check on the model you're considering before being too concerned about this.

On single phase: Again, you might be able to be creative, if you run into the right engineering people. Strong 7kW switching supplies can run 4,000 watt bulbs on single phase power. If you don't need more than that, this might work.

In extreme cases, there are rotary power converters that can provide 3-phase with a single phase input. I'd bet it could work... I ran a large radio station transmitter on one... but if your projector is owned by someone else, it might be a tougher sell. This might be too unusual for someone who's not comfortable with creativity.

Yeah the three phase is for the lamphouse power supply which should be able to run on 240V 3 phase. I have never seen a lamp above 2k run on single phase power.

Some of the small towns near me do not even have three phase power available in their towns.

The Strong 7k switcher is specifically designed to run bulbs up to 4k on single phase power.

We use the 7k supply on our 3 screens, running between 4k & 7kW. We tried the single-phase function last year, and it does work as advertised.

Wow, that is amazing! I would love to get the opportunity to crack one of those open to see how they accomplish that! The problem with using single phase to power DC arc lamps is that the power is not steady. As the sine wave goes "Up and Down" there are flucuations in power. With three phase each leg is "timed" so that each sine wave peaks after another so that when the diode bridge takes out the "bottom" of the sine wave there is one steady line of power. You end up with

---

instead of - - - -

Yep, you're right. That wouldn't be possible with a high reactance supply. Being a switcher though, with the AC frequency being unrelated to the incoming supply, I'd guess it has something to do with that. I'll check what docs I can find, when I get the chance.

Thats great. Thank you, I am interested to find out more about this.

As I have about 45 tanning beds that operate best at 234 volts, we often have to buck or boost the voltage using tranformers. So the min might need to be 208. If it really can only handle 208 vs 240, you would need 2 buck transformers to reduce. Cost about $500 for two (which you will need for 3-phase).
.
My guess is the 240 will work just fine.

Thanks for all of your replies. I feel better about this requirement already. The $$$$ is still a high hurdle.

Isn't it hard for your patrons to see the screen with all the light from those tanning beds???

Or do you provide special glasses to filter out the UV light?

Novel idea though, I like it!

<grin>

I'm still looking for a cheap wat to convert/run a 3p Softserve machine to 1p power... was thinking of running several 1p 220 circuts to it and rewiring the power internally, as everything I see in the machine are 1p motors!

tony.

Is it possible that the compressor might be 3 phase? A high-capacity machine would need a serious freezer, where the beater motor could possibly run on just 2 legs. You might be better off selling your machine and looking for one that'll work with the power you have. The two kinds of available phase converters would be spendy for this kind of application.

[This message has been edited by rodeojack (edited May 31, 2008).]

Here's the text from page 5 of the 5,000-7,000 watt Strong Switcher install manual:

"Connect 208/230 VAC 3-phase input to terminals X, Y, and Z. If operation is limited to 4,000 watts, the unit may be connected to single phase, using terminals X and Z only."

This is for models 62-00018 and 62-00019 switching power supplies.

[This message has been edited by rodeojack (edited May 31, 2008).]

Cinemeccanica an Italian projector manufacturer came up with a scheam in thier V4 projector/pedestal to run a three phase motor on only one phase. They included a circuit with three fairly large capacitors to artificially simulate three phase power. Suprisingly it works fairly well. The only funny thing is that most often there is three phase in the booth anyways for the lamphouse? Seems like it would not have been that difficult to just run thr motor off of the true 3 phase power???

If anyone has any V4's keep that in mind. If you have a motor failure it could be because of an open or shorted capacitor. You will be able to tell if you put a known good motor on it and it sounds like garbage. Running the motor for any real length of time with shorted or open caps will quickly fry your motor.