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Two-Phase and Three-Phase Table saws?

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Forum topic by DustDevil posted 09-01-2008 05:01 AM 13116 views 0 times favorited 19 replies Add to Favorites Watch
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DustDevil

2 posts in 3570 days


09-01-2008 05:01 AM

Hello everyone,

Is anyone familiar with motors out there? I’m not quite sure if I really understand the concept of 2 or 3 phase motors clearly. In order to accommodate a 2 or 3 phase table saw, does one need to do something special with regards to the electrical set-up in the garage?

I know (at least I hope I understand) that I can easily run a 220V outlet from my existing 30 amp subpanel supplying my garage. However, I’m not sure what needs to be done (or if anything needs to be done for that matter) to support these multiple phase motors.

Does anyone happen to know a good resource on the web on general information on motors?

Thanks


19 replies so far

View mski's profile

mski

439 posts in 3979 days


#1 posted 09-01-2008 05:08 AM

You would need a very expensive 3 phase converter in your home.
3 phase motors are cheaper to buy, run , but for home use 220v is where to be.
Yes easy for a 30A sub panel to power 220v.
Google “ac motors”, or ” 2 or 3 phase motors”
Wish I had a Sub Panel in my garage.
Hope this helps.

-- MARK IN BOB, So. CAL

View tooldad's profile

tooldad

660 posts in 3713 days


#2 posted 09-01-2008 05:24 AM

There is no 2 phase motors. There are single phase and 3 phase. There are 2 pole, single phase, 220v tools. These are designed to run in most homes. To run a 3 phase, you need 3 hot leads coming into your house and special 3pole breaker. Chances are unless you have old service or know the electric company personally, you don’t have 3 phase service.

Now, to run a 220v tool, you should be able to run it off of your sub panel as long as there are 2 hot leads coming into the main breaker. I am not a licensed electrician, but I do teach electricity in the classroom. Take that with a grain of salt as far as you want.

Turn off the breaker to the sub panel in the main panel. Remove the cover from the sub panel. Look to see if there are 2 hot leads and a ground lead coming into the panel. More than likely you will have this. Also another indication is if you have breakers on each side of the box (left & right).

If you do have 220 service in your sub panel, it is simple. Just replace or add a 2 pole 20amp breaker in the box, run 12-3 wire from the box, connecting the red and black to each lead on the breaker, the white and copper to the ground bar. Run the 12-3 through the wall or in conduit to your outlet and wire up the outlet. Turn on the power back to the sub panel and you should be good to go.

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Karson

35121 posts in 4399 days


#3 posted 09-01-2008 05:30 AM

I’ve used a 3 phase converter for 25 years. Rotary phase converters are expensive but static are relatively inexpensive. Look on ebay and you can purchase them there.

My table saw has a 3 phase motor and the motor arbor is the saw blade arbor. So it’s not possible to replace it. The phase converter hangs on the wall. I hit the power switch and the saw starts up. It runs with about 2/3 of the power of the plate on the motor. 5 HP run at 3.3 HP The converter manufactures a third phase to start the motor and then the phase converter drops off and you continue on 2 phase power.

A rotary phase converter is the same thing but it has just a motor that is not hooked to any tool. But the motor acts as a generator and it creates the third (missing) phase. Electronic equipment like cad/cam really need a stable phase converter so the static converter can not be used on a CAD/CAM setup.

I’ve been tempted to make my own rotary phase converter and I had a line on a 10HP 3 phase motor but the junkyard scrapped it before they sold it to me. It was a new motor that I could have probably got for $30.00 or so.

Note on the static phase converter they are rated by HP 1-3, 3-5, 5-7.5 or so the 5 HP version might not start a 1/2hp 3 phase grinder. If you have a 5 hp motor running and then turn on the 1/2 hp motor then it will start. The 5 HP motor is acting as a rotary phase converter.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware soon moving to Virginia karsonwm@gmail.com †

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mski

439 posts in 3979 days


#4 posted 09-01-2008 05:50 AM

Karson, I didn’t get this part.
Note on the static phase converter they are rated by HP 1-3, 3-5, 5-7.5 or so the 5 HP version might not start a 1/2hp 3 phase grinder. If you have a 5 hp motor running and then turn on the 1/2 hp motor then it will start. The 5 HP motor is acting as a rotary phase converter.

-- MARK IN BOB, So. CAL

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John Ormsby

1285 posts in 3735 days


#5 posted 09-01-2008 07:23 AM

I run a 7.5 HP rotary phase converter and also have 110v and 220v single phase in the shop. The rotary phase converters may seem expensive, but you can get some good deals on very good used machinery that will easily offset the cost of the phase converter. It all depends on ones needs and uses. There are also quite a few companies that sell rotary converters. The general rule of thumb is that the heavier the rotary converter the better. Mine weighs around 260 lbs and is a high quality one. I can actually run up to 20HP worth of motors at one time. IT is rated at 7.5 HP because that is the highest recommended HP motor one should Start at a time. The rating on other ones may only have the rating stated as the maximum HP for that particular converter. For example, a company may advertise their converter is a 15 HP one. But, in reality it can only start up a 5 HP one at a time. Be careful out there and do some research before getting into 3 phase.

I recommend Kay Industries. They are very knowledgeable. Here is their link.
http://www.kayind.com/tech_center/sizing_tables.html

If one really wants to go for an extreme phase converter, get a digital one. Phase Perfect seems to make the best ones. http://www.phaseperfect.com/press.htm

-- Oldworld, Fair Oaks, Ca

View Catspaw's profile

Catspaw

236 posts in 3814 days


#6 posted 09-01-2008 12:07 PM

There are other threads here that have this discussion. They might provide some additional info, try a search.

Your subpanel may or may not have what it takes. Look in your main panel, at that breaker for your subpanel. If it is a single breaker (taking one space with one handle) you won’t get 220V. It could also be a 1/2 breaker, but, probably not. 220V breakers will span two spaces and the switches will be tied together.

House power is: 2 – 120V legs, 180 degs. out of phase and a neutral (ignoring ground at the house.) Breaker box has 1 buss bar for each leg. These bars zig-zag in and out of each other on both sides. A single breaker picks power off of 1 bar giving you 120V. A 220V breaker spans the zig-zag and gives you 220V.

A static phase converter is not alot of money, maybe $100 to run one item. If you already have a three phase motor in your table saw, it would be a good choice. other wise converting is not very economical. Running a 220V circuit out of your subpanel is simple (if you have 220V at your subpanel.) Converting a 120/240 motor is usually a wire swap in the motor. The diagram is almost always on the motor somewhere. 220V tends to be better in very subtle ways.

-- arborial reconfiguration specialist

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Karson

35121 posts in 4399 days


#7 posted 09-01-2008 03:22 PM

Mark:

What I was trying to say that phase converters come in a particular size, and you need to identify the motor rating that the phase converter will start. If it is a 3HP motor then you need a phase converter that the 3hp will fit in the range. There might be two different versions that will start a 3 HP motor. Both of my 3 phase motors are 5 HP os I opted for a 5-7.5 rating instead of a 3-5 rated convereter.

Then what I attempted to say that if I had a 5 HP table saw running then I could start a 1/2hp grinder if I needed to. I could then turn off the table saw and the grinder would stay running. But I couldn’t start the grinder on it’s own because the motor size is outside the range of the converter.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware soon moving to Virginia karsonwm@gmail.com †

View David Freed's profile

David Freed

113 posts in 3666 days


#8 posted 09-01-2008 04:09 PM

Static “phase converters” are really just motor starters. Once the motor is running, the static converter kicks out and the motor is running on single phase. That will work if you are just doing light duty work, but I would be burning up motors all the time, because I push my machines.
I agree with John when he said “The rotary phase converters may seem expensive, but you can get some good deals on very good used machinery that will easily offset the cost of the phase converter”.
I have a 20 hp rotary converter from American Rotary; http://www.americanrotary.com/. That is big enough for now, but if I need more 3 ph power, I will get another converter from them.

-- David, Southern Indiana

View Moron's profile

Moron

5032 posts in 3892 days


#9 posted 09-01-2008 04:56 PM

I have a 15 hp 3 phase rotary converter used in conjuction with a 600V transformer which permits me to run almost all my tools at the same time (actually just three tools but I can onlymultitask so far).

It wasnt inexpensive and if memory serves me right it was about 5 grand before I got to turn a tool on.

Cheers

-- "Good artists borrow, great artists steal”…..Picasso

View David Freed's profile

David Freed

113 posts in 3666 days


#10 posted 09-01-2008 09:00 PM

roman,

I have a couple questions for you. How does higher voltage make any difference in how many tools you can run? The RPC voltage has to be the same as the motors you are running doesn’t it? Also I would be interested in knowing how you got that much money tied up in a 15 hp converter. I am using 240 volts, so maybe the higher voltage in your setup makes a difference.

Below are some prices from AR. They make RPCs up to 60 hp. I used about $200 worth of wire (I got it for about $30 at an auction a few years ago), and it took about 1 days work running the wire, building a shelf for the RPC, mounting the starter switch (supplied with the RPC), and getting machines hooked up.

3HP Rotary Phase Converters $ 345
5HP Rotary Phase Converters $ 425
7.5HP Rotary Phase Converters $ 525
10HP Rotary Phase Converters $ 695
15HP Rotary Phase Converters $ 945
20HP Rotary Phase Converters $ 1145

Figuring retail on everything;

20 hp RPC $1145
wire $ 200
miscellaneous $ 50
labor (8hrs x $50/hr) $ 400

Total $1795

I actually spent;

20 hp RPC $1145
wire $ 30
miscellaneous $ 50
labor $ 0

Total $1225

-- David, Southern Indiana

View mski's profile

mski

439 posts in 3979 days


#11 posted 09-01-2008 10:05 PM

Karson, thanks Gotcha now.

-- MARK IN BOB, So. CAL

View David Freed's profile

David Freed

113 posts in 3666 days


#12 posted 09-01-2008 10:30 PM

DustDevil,

Do you already have a saw with a 3 ph motor, or are you just thinking about getting one?

Here are some articles about motors, wiring, and phase converters;

http://www.metalwebnews.com/howto/phase-converter/converter-technologies.pdf
http://www.americanrotary.com/rotary-phase-converters.html Scroll down to the FAQs
http://billpentz.com//woodworking/cyclone/DCElectrical.cfm

-- David, Southern Indiana

View John Ormsby's profile

John Ormsby

1285 posts in 3735 days


#13 posted 09-02-2008 12:17 AM

Some machines are imported from Europe and they have a little bit different voltages. For example, My table saw and shaper have a recommended voltage of around 240 volts. I balanced my threes phases to be within one volt of each other at an average of 240 volts. It is true that it will run on as low as 215 volts. However, the lower voltage makes it harder to start and puts more resistance on the switches and electronic boards. This means that there is a much higher potential for a costly repair.The RPC uses what is called a Buck\Boost transformer to balance out the voltages. It is quite important to try to get your voltages as close together as possible. The machines will run properly when done correctly.

-- Oldworld, Fair Oaks, Ca

View DustDevil's profile

DustDevil

2 posts in 3570 days


#14 posted 09-02-2008 02:19 AM

freehardwoods,

I’m in the market to upgrade my table saw to a cabinet type so I’ve been trying to get a better understanding of the options. From the discussion, I gather I probably shouldn’t consider 3 phase equipment due to cost concerns. What would be a major reason to go with a 3ph motor anyways? Thanks for all the links for the electrical info.

Thank you everyone for all the input. Thanks for bearing with my lack of electrical knowledge.

View poopiekat's profile

poopiekat

4355 posts in 3733 days


#15 posted 09-02-2008 02:36 AM

Unless you have commercial buildings in your neighborhood, you might not even have access to 3 phase power from your telephone pole. I would let that drive my decision, after all a good single-phase 220 motor should be all you need. You’re not cutting 4-inch thick tropical hardwoods, are you?

-- Einstein: "The intuitive mind is a sacred gift, and the rational mind is a faithful servant. We have created a society that honors the servant and has forgotten the gift." I'm Poopiekat!!

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