My $45 homemade 10 HP phase converter is WORKING!!!

thanks to everyone for your thoughts!
Many pictures and the story in several chapters:
http://igor.chudov.com/projects/Phase-Converter/
Here's the copy and paste of the text from the webpage:
MAIN PAGE
This text details how I made a 10 horsepower rotary phase converter from $45 worth of parts that I bought from an industrial junkyard gloriously called Pioneer Industrial Services.
At some point, after reading rec.crafts.metalworking and this excellent article on making homemade phase converters, I became excited about the idea of making a rotary phase converter from second hand parts.
I spent about an hour calling around and finally found a guy Dave from Pioneer Industrial Services, who said that he had used 3 phase motors. He has a junkyard full of used electrical components. Here's what I bought, and for how much.
The nice surprise was that the 10 HP motor was possible for me to manhandle alone.
My first prototype was a simple setup with no switch at all, I simply touched the wires to the 240V pieces of the subpanel. Click here to see and read about the first prototype. It sucked and took a long time to spin up, due to poor contacts. It was atrocious.
My second prototype included installation of a 50 amp circuit breaker into the panel, hard wiring of the wires to the breaker, and use of a Definite Purpose Contactor and a regular lamp switch to turn the contactor on. Click here to see and read about the second prototype. This works great, but is ugly and unfinished.
My future plans nclude making a nice carriage on little wheels for the converter, and hiding all electricals inside safely.
WHAT I BOUGHT
I bought the following:
* 10 HP 3 phase Century motor - $40. * 7.5 HP US Electrical Motors 3 phase motor - $20. I bought it just in case. * 30A heavy duty Square D single throw switch - $8. * 50A Definite Purpose 3 wire normally open relay - $3. * Five 535 V 92 mF capacitors the size of a vodka bottle - $5 for all ($1 each).
Dave from Pioneer Industrial Services is highly recommended, he is friendly and his proces are reasonable. I was able to pick everything that I needed, from him. He is in Addison, IL.
FIRST PROTOTYPE
The very first try was quite simple. I spun the motor by hand and then applied power. No capacitors. The motor was finally able to accelerate, after much difficulty. That proved to me that it was not "fried".
My first prototype was simply a test of the concept -- would a three phase motor spin up like they say, if I apply capacitance between one power leg and the generated leg?
I wired the motor as follows: two legs of 240V were connected to the two legs of the motor. These I call Leg 1 and Leg 2. Leg 3 was connected to Leg 1 via three capacitors wirted in parallel. You can see that on pictures.
That made the motor spin up reliably, but slowly due to very poor contact between my wires and the subpanel. After that, I decided to try better wiring. See next chapter.
SECOND PROTOTYPE
Since the concept obviously worked, I now wanted to go a little bit farther and wire it more properly.
I wired it as follows. I installed a 50 A crcuit breaker in the subpanel. I hard wired the 8 gauge wires with one end into the breaker, and another into the 3 pole definite purpose contactor.
The contactor is a neat thing that, when 110 V is applied to two sensing contacts, with very little current drawn from 110v it closes the big contacts for all three poles.
Legs 1 and 2 of utility 240V were connected to legs 1 and 2 of the motor. Leg 1 (on the motor side, not on utility side) was ALSO connected to one side of the capacitor bank. Leg 3 (the wild, generated leg) of the 3 phase motor was connected to the other side of the capacitor bank. That's how self starting phase converters should be wired according to this excellent article on making homemade phase converters
The converter now would spin up in less than a second. My next task was to measure voltages between legs, which would be suggestive of the actual degree of phase shift. The voltages were as follows: 256 V utility, 239V, and 271V. I did not like it.
I then removed one 92 mF capacitor from the bank, leaving only two capacitors with the total capacitance of 184 mF. The effect of this was that instead of less than a second, the motor would spin up in about one second. Not a big deal to me. The voltages now were as follows: 256 V utility, 240V, and 260V. I decided that I should go with two capacitors.
Costs of parts actually used, so far:
* 10 HP motor -- $40 * Definite Purpose contactor -- $3 * 2 capacitors, 92 mF each -- $2
The total cost, so far, is $45. Wires and new breaker do not count.
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Sorry, the breaker is 60A.
i
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Ignoramus23077 wrote:

Wow, you certainly work fast! Glad it's working so far. It looks like you got some nice equipment at good prices, too. Your induction motors look quite different from the ones we usually get in the UK. The majority of our three phase motors are either the standard aluminium TEFC motors or the older cast iron type, of which there are still many around. Yours look somewhere in between these.
For the experts on phase convertors, I've got a couple of questions. I'm thinking of building the kind of convertor Dan Caster was talking about, where a small single phase motor permanently drives a larger three phase motor through a variable belt drive. The three phase motor has two terminals connected to the single phase supply and generates on the third terminal, and the belt drive ratio is adjusted so that the single phase motor draws its rated current when the phase convertor is working at maximum output.
Now my questions. Firstly, will the quality of the three phase output be improved if the single phase motor is larger than a typical pony motor (e.g., 3/4 hp single phase motor and 2 1/2 hp three phase motor)? This seems logical to me, as there is more torque applied to the shaft of the three phase motor which can assist in generating the current which flows from the third terminal, but it's such a complicated situation - what do other people think? (It also happens that I can get the 3/4 hp and 2 1/2 hp motors cheaply and easily.) Secondly, would the addition of a flywheel to the idler motor shaft (not necessarily together with the permanent drive from the single phase motor) help balance the output? Again, I intuitively think it would, but I'd be interested to hear the views of others.
Best wishes,
Chris
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On Thu, 28 Jul 2005 03:52:15 +0000 (UTC), Christopher Tidy

Yes, surprisingly, my junkyard trip provided me with all necessary parts.

I think that it is a former compressor motor.
i
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No difference in the 3 phase output. The pony is needed only to provide enough RPM of the 3 phase idler so it will spin up to its no load max RPM. Once the idler is spinning, the pony can be disconnected.
SNIP
>Secondly, would the addition of a

No again, the idler RPM doesnt vary (measureably) with toolmotor load related RPM. Actually, the flywheel hinders the idler's acceleration when it is initiated.

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Very interesting, but what is a phase converter used for? Since this is alt.home.repair, do I need a 10 hp phase converter? Just puzzled :-)
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Walter
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Let's say that you want to build a house addition. You need a table saw. Your neighbor has a cheap 3 phase 3 HP powermatic table saw for sale. A phase converter would be quite useful!
:)
i
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On Thu, 28 Jul 2005 05:08:51 GMT, Ignoramus23077

Speaking of which..I have a nice old Oliver 12 or 14" table saw for sale. All cast iron...and 3ph. $300 takes it.
Gunner
Liberals - Cosmopolitan critics, men who are the friends of every country save their own. Benjamin Disraeli
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Ignoramus23077 wrote:

Im lost. Are you generating mechanical power or electrical power?
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Respectfully,


CL Gilbert
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wrote:

My phase converter generates mechanical power by spinning the rotor, and then mechanical power of rotation is again converted to electrical power on the third leg.
i
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On Thu, 28 Jul 2005 08:53:38 -0400, "CL (dnoyeB) Gilbert"

Chuckle...Ill try to explain this...
Most US homes use single phase power. This means there are two wires in the outlets, plus a ground. It can be 120volts or 240 volts, but there are just two "hot" wires (over simplification for ease)
Industrial machines use for the most part...3 phase power. There are 3 hot wires. and will not run properly on only two. They heat up and burn out quickly or refuse to start.
There is a lot of surplus industrial machines available, for very little money that work very well for home use. Even a moderately worn industrial machine is likely 3x as well made as a brand new Chinese big box store machine. An example would be a Ryobi table saw from Home Depot, versus a Delta UniSaw from an industrial auction. One might last a year or two...the Delta the rest of your life.
So a way must be found to allow a 3 phase machine to be run on single phase power. Hence we have rotary and static converters (and a few other ways) which make up the 3rd hot wire.
Such a converter allows you to run industrial type machines on the 240 volt power that comes into your house. Plug the converter into your electric dryer outlet and now you can use that Delta UniSaw, as an example. Lathes, milling machines, drill presses, heavy industrial welders, etc etc are all available, and most often are not even available in single phase models. Hardinge Lathes, are an example. Due to many factors, the machine cannot easily be changed over by replacing the motor with a single phase one. So has to be run on 3phase power. Again..we use a converter to generate that third hot wire so it can be run off your dryer outlet.
Help any?
Gunner
Liberals - Cosmopolitan critics, men who are the friends of every country save their own. Benjamin Disraeli
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| thanks to everyone for your thoughts! | | Many pictures and the story in several chapters: | | http://igor.chudov.com/projects/Phase-Converter/ |

I don't know jack about RPC's, so I just ask this as a sounding board for those among us who can verify my concern. Should your contactor have an overload on it? The overload's job is to protect the equipment if an overcurrent exists on any or all legs. In essence, it shuts all three phases off even if one has shorted to ground. Your supplier will have some or you can trade the contactor in for one that has it. Overloads come with a holding contact that turns off power to the contactor if an element overheats. I know that current in one leg will be lower in an RPC, but as long as it doesn't exceed the overload element's rating it will work just fine.
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Yep, Carl is right about the protection considerations.
The overload protection devices aren't just to protect against the motor developing a short to ground, they react to protect the motor from being overloaded by a jam or machine malfunction/breakage, stalled or any other condition that causes the current to rise to a point where the motor would be damaged/destroyed by the resulting heat in the windings. The OLP's heaters are selected from a chart of currents for the specific motor being used. Some OLPs have adjustable trip settings so that heaters don't need to be selected. Each type of OLP will cause all 3 phases to be opened/interrupted.
The OLPs are also available as a separate device, but are commonly integrated into the overall starter/contactor box.
The best setup for an RPC would be a magnetic starter/OLP rated for the size of the RPC motor, and a separate (specifically sized) starter/OLP for each machine motor that's powered from the RPC. Choosing not to use a second, separate OLP for the (usually) smaller machine motor will not offer any protection for the machine motor.
WB ................

an
some
with
-
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Hm, I am confused. I agree with you on the need for overload protection. I will install something, for sure.
What I am curious about is, can I simply use motor rated fuses on both incoming 240V legs? That should provide all necessary protections for the idler.
I do not mind installing an overload relay, as such, except that it is a cost issue. Fuses are cheaper. (unless I can find something at that junkyard). Realistically speaking, the idler is not going to bind. If contacts to capacitors break, yes, I could have a stall issue, which would be addressed by properly sized fuses.
A relay is more exciting and possibly a little more convenient (it is resettable, I do not need to buy new fuses when a fuse burns out), but in reality will provide about same protection.
Am I mistaken?

Yes, I saw some on ebay last night...

Agreed.
Agreed also.
i
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I
Fuses can be expensive and overload heater type contactors are even more expensive. If you use this RPC and tool fed by it, are used only when you are "in attendance", you wont need any fuses, your 60 amp breaker will trip before you burn anything up. If the 3 phase tool motor stalls for any reason, just hit the kill button on the RPC.
Jerry
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Hm, that's nice to hear. I will think about it.
i
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Ignoramus9394 wrote:

The overload units in a motor starter are have a very narrow operating range like 57.5 - 61.3A that can be very closely matched to the motor rating. Picking between a 50-60-70A fuse doesn't give much protection. Also overloads are designed to allow the starting inrush and are designed to match the thermal characteristics of the motor for overload. Even time delay fuses have to be much larger than the motor rating or they will blow on the starting inrush. Fuses can be sized at up to 175% of the motor rating and circuit breakers up to 250%(NEC). The fuses in a motor circuit are intended to provide short circuit protection, not overload protection.
Bud--
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| I do not mind installing an overload relay, as such, except that it is | a cost issue. Fuses are cheaper. (unless I can find something at that | junkyard). Realistically speaking, the idler is not going to bind. If | contacts to capacitors break, yes, I could have a stall issue, which | would be addressed by properly sized fuses. | | A relay is more exciting and possibly a little more convenient (it is | resettable, I do not need to buy new fuses when a fuse burns out), but | in reality will provide about same protection. | | Am I mistaken? |
Your 220V home circuit breaker has two poles, but each pole is connected so that if one leg has an overcurrent, it will trip, taking the other leg out with it. Otherwise, one leg will still be hot, presenting a very ugly hazard. Fuses cannot provide this protection, and as such, are a single shot deal. Overloads, on the other hand, have various trip conditions that can be selected for, and they take all three phases out at the same time, which is the safety you need.. Ask your supplier for assistance in picking them, I don't have that information at hand anymore. While motor starters have the contactor and the overload physically attached to each other, electrically they're pretty much the same so one brand ought to be usable with another even if you can bolt them together. Just for the sake of the record, a motor starter consists of a set of three large contacts, possible auxiliary contacts (usually clipped or screwed) and the overload. The overload has three fuse looking elements that are called heaters. When the heater gets to a certain point in its thermal cycle, it will bend and trip the overload, which actually just opens it's own auxiliary contact and the contactor opens up. The solenoid on the contactor is wired through this overload contact, so in order to reset it you usually have a reset button to push. To add a little more confusing information, starters are given sizes, according to NEMA, thus you have a starter for a given range of motor sizes. http://www.southlandelectric.com/Thermal%20heater%20elements.htm has a lot that info that might help you understand better. The overloads are sized to match as well.
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Thanks. That's very helpful!
i
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Ignoramus23077 wrote:

No problem. Glad to share.

Hey Ignorant, for $10 more you could have built an electric chair, tried it out yourself and we'd never hear from you again. Think about it for your next project.
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