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Jonathan Dennis

Wed Aug 12 2009, 09:35PM

Registered Member #2153 Joined: Wed Jun 03 2009, 03:19PM
Location:
Posts: 69

Hello all, I just bought a very nice Laser Show system. However the power supply box has a special power need, beyond the typical wall outlet. It requires 3 phase power running 30-40 Amps, and 190-220 Volts. I need to find out how to wire up this kind of power supply for it. It's previous owner had it straight wired, so it's just the bare wires. Please help me out with this. Most importantly, I need to do it on a budget! I can't afford a brand new phase generator for 1-2,000 dollars.

Thanks

klugesmith

Wed Aug 12 2009, 11:29PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Where do you want to run it, and what kind of electric power is available to start with?

IamSmooth

Thu Aug 13 2009, 12:14AM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
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Posts: 1567

You are looking at over 8.8kw per phase. That is almost 27kw of power. Most homes are wired for 100A into the home at 220v and your power requirements exceed this amount. You will probably need to get your home rewired. $$$

Jonathan Dennis

Thu Aug 13 2009, 04:17AM

Registered Member #2153 Joined: Wed Jun 03 2009, 03:19PM
Location:
Posts: 69

Ok, the manual that came with the laser says that the power control box has a variable transformer inside that can be adjusted based on the available voltage. The minimum being 190 VAC. However it still requires 35Amps of 3 phase, and someone that builds them told me that each phase needs to be 35A, whatever that means. Wouldn't that be 105 Amps total? It says on the back of the power box that it runs on 35A, not 105. If I cannot get a 3 phase source for a reasonable price, I might consider a 3 phase generator, if anyone knows much about these. An electrician friend of mine said you can get a special box that is wired from a standard home outlet that converts to 3 phase for about 3-350 US dollars.

klugesmith

Thu Aug 13 2009, 05:00AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Jonathan,
Can you be more precise about the unit's input voltage requirement?
I bet it's designed for "120/208 volt wye" (120 volts from each phase to neutral),
which is the most common 3-phase voltage in the walls of US office/industrial/commercial buildings.
So your gadget might be within the power capacity of your US domestic grid connection.

Hobbyists with lathes & milling machines in the garage often use homebrewed rotary phase converters,
though usually smaller than you would need. I met a farmer who contrived one to power his 3-phase irrigation pumps.
Google can help you learn.

If you want a pluggable power cord, it won't be cheap. Some of the machines I help to design are ordered with plugs like this:

Jonathan Dennis

Thu Aug 13 2009, 05:20AM

Registered Member #2153 Joined: Wed Jun 03 2009, 03:19PM
Location:
Posts: 69

Ok, the power supply has a Variable transformer built in. It can handle 190-250 Volts, the variable transformer simply has to be adjusted accordingly. However it requires minimum 35A up to 50A, but 50 is pushing it a bit. I don't want to attempt making my own phase converter, because first I start college in less than 2 weeks, so I need something quick, and second I wouldn't have the slightest idea where to begin. I'm sure google could teach me, but not in the alloted time unfortunately.

klugesmith

Thu Aug 13 2009, 05:32AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

[edited while you were replying, sorry]Are you prepared to buy a solution for $100s or $1000s based on tips from this forum,
so you can play with big lasers without having to learn about electricity?
If you are on a budget and are patient:
During first term at college, find a lab or shop with a suitable power receptacle.
Then if you haven't lost interest, bring the laser machine with you for 2nd term.

Jonathan Dennis

Thu Aug 13 2009, 05:36AM

Registered Member #2153 Joined: Wed Jun 03 2009, 03:19PM
Location:
Posts: 69

Sorry, can't return it, I got it for a great price and am hoping to make some money on it. Are you sure I cannot just order a 3 phase static converter? They are reasonably priced and seem to meet the requirements of this system? I wish I could take it to college but it's HUGE and lots of heavy pieces, much unlike the common handheld laser pointer. haha

btw, I have learned alot about electricity from building my tesla coil, I'm not lazy. But when you have something this spectacular sitting, begging to be turned on, you have a slight sense of urgency in figuring out how to get power to it. Someone on a laser forum recommended this. Tell me what you think:

The power supply sounds like it requires about 4kW at full power. You probably won't be able to draw this from your domestic supply (at least not from a single circuit), so you probably won't be able to run at full power. Maybe you can parallel some circuits on the same phase, or make a high current connection at the fuse box.

To run the power supply at reduced powers, neither static converter or rotary converter are likely to be necessary. If you look inside the power supply, I expect the three phases are connected to a 5-terminal bridge rectifier, which is in turn used to charge a main filter capacitor. It would be purposeless to generate three phases just to recombine them this way.

To run at low powers, you could connect active and neutral (of your single phase system) to any two of the three phase inputs. There are probably also single phase circuits connected across two of the three phase inputs inside the power supply. In that case, naturally those are the two inputs you will have to use.

Please don't attempt any of this unless you know exactly what you're doing.

Steve Conner

Thu Aug 13 2009, 09:46AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

What kind of laser is it? I'm going to guess argon. You might be able to modify the power supply to run off 220V single phase, by connecting the variac stack up in parallel and adding a bunch more smoothing capacitors.

Argon would also explain why you got it cheap. Argon laser tubes wear out after a while. Did you ask the seller how many hours were on the tube?

Jonathan Dennis

Thu Aug 13 2009, 01:58PM

Registered Member #2153 Joined: Wed Jun 03 2009, 03:19PM
Location:
Posts: 69

The tube itself was recently regassed, the red however is low. but it still works great. I understand the theory of modifying it to run on single phase, but I don't think I could figure out how to do that. I've been looking at rotary 3 phase generators which seem to be the only option, but they are very $$$. I can't find any used.

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