BOUGHT motors and stuff for PHASE CONVERTER

SO, today I visited this junk yard called Pioneer Industrial Services.
Here's what I bought:
1. 10 HP Century 230/460V 3 phase motor, clean looking: $40
A nice surprise about this motor is that it is not that heavy, perhaps 150-180 lbs. I can handle it alone.
2. 7.5 HP U.S. Electrical Motors motor, dirty looking: $20
Both motors spin freely.
3. Five 92 mF 500+ volt oil filled run capacitors, each the size of a vodka bottle, no PCB: $5 for all five. The owner did not know what they were, I pretended that I did not know either. I said, these pieces look interesting, I will give you $5 for them, maybe I will use them for something.
4. A big Square D safety disconnect, $8
5. A contactor, possibly wrong for the application, $3
The guy is actually nice and pleasant and sensible. I also dropped off a huge transformer that I could not get rid of otherwise.
My plans are as follows: I will make a self starting rotary phase converter, as outlined in
http://www.metalwebnews.com/howto/ph-conv/ph-conv.html
(see "Self Starting Phase Converter")
I will use 3 of my 92 mF capacitors, connected in parallel, between leg 1 and leg 3 of the 10 hp idler, if I use a 10 HP idler.
I will create a web page about this project.
I have a question, is there some convention about leg numbering and direction of the rotation of motor shafts? I do not want things to rotate backwards and I want to do that in some conventional manner.
I really liked that junk yard, I will definitely go there again.
i
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On Wed, 27 Jul 2005 13:42:02 GMT, Ignoramus23077

It makes no difference which way the RPC turns. And you can buy meters which will tell you the direction of rotation by spinning the motor by hand. But it really doesn't matter for most equipment. As each new machine is hooked up turn it on momentarily and see if it turns the right direction. If not, swap any two wires and it will spin correctly. The only thing I do is to make sure I know which wire is the manufactured leg at each machine. Some CNC equipment, especially older equipment, can only tolerate the different voltage on one particular leg. Fanuc controls can be this way. So you may need to experiment. All that usually happens is that the machine will not start. Manual machines with reversing switches work by swapping two legs of the incoming power anyway so hooking up the machine and just applying power momentarily should not cause any damage. ERS
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Thank you Eric. I recently sold a 2 HP vacuum pump, which I am rather regretting now that I am building a RPC.
i
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wrote:

Typically L1. Not always..but typically.
Gunner
"This device is provided without warranty of any kind as to reliability, accuracy, existence or otherwise or fitness for any particular purpose and Bioalchemic Products specifically does not warrant, guarantee, imply or make any representations as to its merchantability for any particular purpose and furthermore shall have no liability for or responsibility to you or any other person, entity or deity with respect to any loss or damage whatsoever caused by this device or object or by any attempts to destroy it by hammering it against a wall or dropping it into a deep well or any other means whatsoever and moreover asserts that you indicate your acceptance of this agreement or any other agreement that may he substituted at any time by coming within five miles of the product or observing it through large telescopes or by any other means because you are such an easily cowed moron who will happily accept arrogant and unilateral conditions on a piece of highly priced garbage that you would not dream of accepting on a bag of dog biscuits and is used solely at your own risk.'
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...

...
Now I know I'm not typical. I've redone a whopping three machines where this mattered. All three had the wild leg on L2.
Karl
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Iggy sez:
"I will use 3 of my 92 mF capacitors, connected in parallel, between

That would be about right for a 10HP idler motor unbalanced RPC. It is close to the rule of thumb for 30 uFd per HP. It will probably make you a fine RPC. Now, here is where a problem may occur:
You specified a "Hanrahan" Self-starting RPC. It is unlikely a 10 HP motor will start reliably - i.e., without excessively long spin-up time drawing heavy current and popping breakers, etc. IMO, you will need to include a capacitor start circuit. It doesn't have to be elaborate with voltage sensing relays, or such. Between the same line side and 3rd leg where the run capacitance is connected, connect a momentary push button and some electrolytic (start) caps. You will need in the neighborhood of 700 - 800 uFd. I would suggest trying 1 of the 270 - 324 uFd nom., start caps as sold by Grainger. That would give you around 600 uFd counting the 3 92's of run cap you have connected. If that isn't enough to start in less than 1 second spin-up time, increase the amount of electrolytics. Never leave this type of RPC unattended. In the event of power failure, when power is restored, the motor would be attempting to start with insufficient start capacitance and might burn up and/or cause a fire.
Be careful, the voltages involved can be lethal.
Bob Swinney
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I thought that meeting the spec of capacitance is enough to get the motor to spin up quickly. It will be on a 60A circuit. I just bought a 60A breaker at Home Depot.

Bob, I am confused, the author of the web article that I referred to, considers his run capacitor of 30 mF/HP between legs 1 and 3, to be sufficient. Are you saying that he is wrong?
i
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The source you quoted in your post was re. the Hanrahan self starting RPC. No, Jim Hanrahan is not wrong - far from it; but his paper cautions that the usu. 25 - 30 uFd / HP may be insufficient for starting the idler, leading to long start times and tripped breakers. Also, he mentions the amount of (excess) run capacitance necessary for proper starting may lead to high 3rd leg voltage. I'd advise you to go ahead and try it and gather some useful information in the process. You do have a voltmeter don't you? It may be possible for you to make a self-starting RPC that will be just fine - there are slight differences in motors that may work in (or against) your favor toward being truly self starting. Please let us know how it comes out.
Bob Swinney
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Thanks. I already put the phase converter together. I just made a post to Rec.Crafts.Metalworking about it, feel free to follow up with your thoughts. Pictures and story are here:
http://igor.chudov.com/projects/Phase-Converter/
Regarding what you said, empirically speaking, two capacitors work best, at least without load.
i
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On Thu, 28 Jul 2005 02:46:17 GMT, Ignoramus23077

How much did the elephants cost?
Gunner
Liberals - Cosmopolitan critics, men who are the friends of every country save their own. Benjamin Disraeli
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A dollar each at a junk yard. The owner did not know what they were. I saw them and asked him, do you know what these things are? He said that he did not know. Then I offered him $5 for all five, I said, maybe I can find some use for these things, whatever they are.
I hope that I did not get screwed on this deal, 535 V run caps of this size should logically be worth more...
i
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On Thu, 28 Jul 2005 07:51:08 GMT, Ignoramus23077

How much does it cost to feed em?
Gunner
Liberals - Cosmopolitan critics, men who are the friends of every country save their own. Benjamin Disraeli
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Ig
If this first assembly of a RPC doesnt have to be your final attempt to build the converter, I suggest that you consider something simple like the pushbutton start that Bob refers to. You can include tuning capacitors and/or power factor correcting capacitors later, if needed. If you have interest in a switch for connecting the start capacitor with a solid state switch, E-mail me for details. The reactive voltages asociated with disconnecting the start capacitor can be rough on switches.
Jerry


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Ignoramus23077 wrote:

Point of question - is that 30 mf per HP or 30 mf divided by HP rating value.
e.g. 300mf for 10hp ?? - 3mf if 10hp ??
Wondering. Some short hand isn't handy.
Martin
--
Martin Eastburn
@ home at Lion's Lair with our computer lionslair at consolidated dot net
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On Wed, 27 Jul 2005 22:56:39 -0500, Martin H. Eastburn

The logic is, the more HP, the more capacitance. Supposedly, the relationship is linear. That means that for every HP added, a certain, given amount of capacitance must also be added. So, then, using a term of mF/HP is proper.
i
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Ignoramus23077 wrote:

/ == per == divide. Was this a hardware store item or a math issue. Martin
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@ home at Lion's Lair with our computer lionslair at consolidated dot net
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