Need 3 phase Assistance

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438
Location
Grand Rapids, MI
As I am doing research into wiring 3 phase circuits, I keep coming up short. I mean, things are still a little hazy, and I would love help nailing down the details.

1.) Assuming I am using 10 gauge wire, do I need 3 conductors and a ground, or do I also need a neutral? For some reason I seem to be getting mixed messages in this department.

2.) What's the least expensive way to get power to the four 3 phase tools. Meaning, how do I connect four loads to the one power source with the least expense? Do I need a 3 phase load center (breaker box), or do i just run all the tools into one junction box and feed it directly from the converter?

3.) Do you have any pictures of your 3 phase wiring/circuits?

Thanks for any help you can give!

Hutch
 
1.) Assuming I am using 10 gauge wire, do I need 3 conductors and a ground, or do I also need a neutral? For some reason I seem to be getting mixed messages in this department.

you will need 4 conductors

2.) What's the least expensive way to get power to the four 3 phase tools. Meaning, how do I connect four loads to the one power source with the least expense? Do I need a 3 phase load center (breaker box), or do i just run all the tools into one junction box and feed it directly from the converter?

If you are running multiple circuit each one should have it's own branch circuit protection. If you will not be running all the loads at the same time you can put a seperate plug on each one and plug it into the source.

Fell free to ask as many questions as you need since we don't want anyone getting hurt.
 
Ok.....

So, being a novice, can you clarify the wire type? Do I need 10/3 with ground, or something else?

Also, I really don't need the tools on separate circuits at this point. Running the receptacles in series should be adequate, right? (I don't plan on running more than two tools at once, and even that's not likely.) With that said, since a breaker is protecting the phase converter, could I run the circuit from the converter to the tools with no disconnect in between?

Thanks!

Hutch
 
10/3 w/ ground is fine. I remember a discussion on another board about running 4 recepticles off 1 breaker which caused me to break out my NEC book. you'll be fine running 4 recepticles off of 1 breaker. The rule for running seperate circuit only applies for hard wired loads. The circuit braker is fine, no additional disconnect is necessary.
 
Nice!

Thanks Don! I really appreciate the info!

SO here's another question. The idler motor for the converter is 10 hp. If the converter is on a 60A breaker, if a tool's motor is overloaded is it possible for the breaker not to trip? I mean, the combined amperage of the idler and machine (even a machine under load) will not be anywhere near 60 amps. But is this 'not properly tripping' idea faulty since the breaker is back on the single phase side (where the amperage has to be multiplied.)?

Hutch
 
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matt,
wire size is determined by amp draw, 10ga wire is suitable for 30amps.
30 amps of 220 3-phase (low voltage) is about a 10hp motor.
3-phase motors will run just fine without a ground but it is a very good idea to install one for safetys sake. also if there are any single phase controlls on your equipment (most have) they will make use of the ground wire to complete their circuit.
i do not use a convertor so can`t offer advice on building one.
if you are using 10ga wire leaving the convertor you should install a breaker no larger than 30amp between the convertor and the 10ga wire.
breakers are designed to protect wire not motors.
if you want to add motor protection it is best to fuse each line at the controlls.
 
.....breakers are designed to protect wire not motors.

You can not hear that enough. Had this very conversation with clients yesterday about a fuse panel that the fuses (not breakers) had been replaced and with to large a fuse.

I think I have plans for a 10hp phase convertor. If you scrounge parts it will cost you about $250 to build but it is one of the best designs out there. A friend of mine has been developing it over 10+ years and while not cheap, I really believe his are the best out there. Bruce is always willing to help someone new build one, he lives for this stuff.

You hit a button, it starts and works with no drama! I am very impressed with mine.
 
Hm

Thanks for the clarification. I guess I wasn't really thinking quite right about circuits, even though I actually did know that breakers are for protecting wiring. How quickly I forget.....and that's why I post electrical questions on forums. :D

Do you think it's necessary to protect the motor?

As for the converter, I have already purchased one. Spent about $300 for the converter box, but I still need a 10 hp motor for it. Too bad I didn't post something before I bought it!

Also, I don't think there are single phase controls on my machines, but I will have to double check that. The machines I will be running are an 8" jointer, a 3hp Rockwell Unisaw, a 5hp 14" Rockwell RAS, and eventually I will be upgrading the drive system on my big lathe to a 3hp 1100 rpm motor with a VFD.

Anywho, thanks for straightening me out! :)

Hutch
 
There are Circuit breaker designed for motor protection. The are labeled MCP for Motor Circuit protectors. I prefer them to fuses since not only do they protect the motor froom overload but they also offer protection from single phasing in the event 1 fuse blows. leaving to 2 hot legs to the motor. For three phase circuits on 220/230 volts you can figure the FLA as 2.3 amps per horsepower.
 
Cool!

Good stuff! Thanks Don, that really helps to narrow things down. When I have tried to do searches on industrial supply websites I get overwhelmed and confused cuz I have no idea what half the stuff is for. :)

Hutch
 
One more thing. In deciding the wire size the code call for you to size everything for 100 percent of all of the loads and 150% of the largest load. e..g is you have 3 7 amp load and 1 10 amp load then size it for 3x7+15=46 amps. again if you are only going to run 1 machine at a time then 150% of the largest load.
 
Awesome!

Thanks again!

I think I may post a diagram of the final wiring plan just to make sure I am not overlooking something important, but I think I have a pretty good idea of what needs to be done. And if y'all think of anything more, please drop me a note.

Hutch

P.S. Actually, I have a question still. So I need an MCP at each machine, sized for that motor?

P.P.S. Something like this?
 
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I can handle the basic wiring, switches, plugs and receptacles, but I'm ignorant about the advanced electricity stuff, what is the advantage/purpose of having 3 phase electrical in the shop??:huh: :huh:
 
I can handle the basic wiring, switches, plugs and receptacles, but I'm ignorant about the advanced electricity stuff, what is the advantage/purpose of having 3 phase electrical in the shop??:huh: :huh:

Dan, I know considerably less than you about elektriks.
To answer your question from my perspective: If I get a piece of equipment that says '3 phase' (whatever that means), I pick up the phone, call a retired electrician friend and say "HELP". When he is done, I pay him his very reasonable fee and use my equipment, still happily iggerant.
 
My Reasons

Well, in industrial settings it has a lot do with electicity usage (a single phase motor draws a ton more current than 3 phase) as well as balanced current (many industrial machines require balanced current). But there is also delta and Y circuitry, and a bunch of stuff I don't understand yet. I obviously don't know very much about it. :huh:

BUT.....my reasons are very simple: flexibility. 3 phase woodworking machines kept coming up for sale, and some were REALLY sweet deals. I passed them up cuz I wasn't prepared to buy a converter. But as I have been developing a shop vision (that is, what I would like to see happen in the long run), I decided I should have 3 phase. I think being able to buy 3 phase equipment (I have three 3 phase tools right now) could prove invaluable. Plus, I have a lathe I want to upgrade down the road, and 3 phase is the best route and least expensive. Over time, having 3 phase will allow me to get better tools for less money (or at least better tools :)).

Hutch
 
Dan has it in a nutshell. Industrial machine mostly run on three phase and when you get into bigger machine's 7.5 HP and up they are all 3 Phase. The largest 1 Phase motor I've seen is 5 HP. Three phase motors are also smaller and weight less. For the hobbest they only real advantage is the avaibility of used equiptment wich can be bigger and less expensive then motors with 1 Phase.
 
I can handle the basic wiring, switches, plugs and receptacles, but I'm ignorant about the advanced electricity stuff, what is the advantage/purpose of having 3 phase electrical in the shop??:huh: :huh:

Dan, if you have a fancy bicycle with the shoes that clip to the pedals so you can both push and pull. single phase is like having one pedal. No starting torque at all if you are at the top or bottom of the stroke when you stop, so you do some tricks to get going (the starting capacitor on a motor), and with a lot of effort you get up to speed. Once you are going, you can keep it going just fine.

Now take that same bike and put on three pedals (don't ask where you are going to get three feet - just pretend). You can push and pull on each of the pedals, but since they are spaced evenly around the wheel, no problem getting started and running smoothly. Just like three phase power.

But three phase power requires three distribution lines, three transformers on the pole (or wherever they are hidden in your neighborhood), etc. In residential areas, rather than bringing all three phases to each home, a few houses are driven from one transformer, then the next transformer serves a few more, etc. Or one phase goes around each block. Since homes don't have big motors that stop and start a lot (like an elevator), no problem. But a big problem if there are big motors. (I am one up on Don, since I have seen a 10 hp single phase motor, but the recommended configuration was to get the 10 hp motor in 3 phase.).

Three phase is not significantly more efficient, but it is sold on a different basis than home power. A much lower price per KWH power used, but a separate charge for the delivery system, based on the peak "demand" measured by a separate meter.

I have a whole web page on 3 phase power if I haven't put you to sleep yet... see www.solowoodworker.com/tools/power.html
 
Great summary Charlie - thanks for the link to the article, too.

It is possible to start out on the cheap with 3 phase, if you have to. When I started my business in the garage I got a 2-5 HP static converter, and used it to run a 2 HP dust collector, 3 HP table saw and jointer, and a 5 HP shaper. The static converter can also become a component for an idler motor, to make a rotary converter to generate the 3rd leg. In fact, the more motors ran at once, the better the power got as the largest motor became a sort of idler for the others. The only trick was needing to make sure that the mag starters were wired to the 2 hot legs. I put all of my equipment on SO cords with twist lock plugs and receptacles, so I just wired in a string of J boxes and outlets in parallel after the converter.

Yes you lose 30% of the power when running a single motor, but a static converter does let you get going on the cheap.

I have since moved to a commercial building with 3 phase, and have transformers (and in one case, load center for) for 380, 460, and 600 V. Used transformers are less expensive than rotary converters, and are another way to run equipment that is not plug-and-play...
 
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