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Generators & Electric Motors General Discussion

120v single phase motor turning 3 phase generator


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  #1  
Old 10-01-2014, 11:47:35 PM
gibbykart gibbykart is offline
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Default 120v single phase motor turning 3 phase generator

Hello, I'm nirmaly stuck in steam land but I had a question and wanted a answer. I have many 120 motors laying around and was given a 3 phase generator when I purchased my M-head Bridgeport mill. My question is, Could I couple a 120 single phase motor to my 3 phase generator and create 3 phase power for my mill? I'm not talking rotory phase converter, I just want to hook the 2 together and wondered if it would work. Thanks -Mike
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  #2  
Old 10-02-2014, 12:43:06 AM
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Jim McIntyre Jim McIntyre is offline
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Default Re: 120v single phase motor turnig 3 phase generatot

Yes, that'd work.

If your M head is 1/2HP, you'd probably want a generator of at least 2 kW, and maybe 2-3 HP motor driving that? Just a guess - you might not need that big of a generator, especially if you don't do any plug-reversing on the BP...
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Old 10-02-2014, 07:20:46 AM
jpatrickc jpatrickc is offline
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Default Re: 120v single phase motor turning 3 phase generator

That will work fine as long as the motor speed matches the generator. I think you would want to direct couple the units or use a cog belt to prevent slippage. I have worked with motor-generator sets that we used to provide 50 Hz power for equipment we were building for foreign markets.

Pat
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Old 10-02-2014, 08:26:50 AM
gibbykart gibbykart is offline
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Default Re: 120v single phase motor turning 3 phase generator

Thank you gentlemen, now I'm going to go jump on my engine and steam off so I can leave you alone. -Mike
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Old 10-02-2014, 10:33:08 AM
Radiomike Radiomike is offline
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Default Re: 120v single phase motor turning 3 phase generator

You do not say what size your three phase generator is you will need a motor at least as big to spin it. If it is a single phase induction motor, these do not run at synchronous speed but some 3 to 4% lower. So if direct coupled you will only get around 58Hz.

Mike
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Old 10-02-2014, 03:44:53 PM
gibbykart gibbykart is offline
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Default Re: 120v single phase motor turning 3 phase generator

Well maybe i should Check to see what you guys think would work for the .5hp m head mill for the generator, i just bought one and thought it would work, the company said i can exchange for bigger or smaller at anytime, can anyone tell me what size single ph motor they would recommend to use with the indicated 3 phase gen when someone says what they would recommend for that? Thank you -Mike
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Old 10-02-2014, 04:26:52 PM
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Default Re: 120v single phase motor turning 3 phase generator

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Originally Posted by gibbykart View Post
Well maybe i should Check to see what you guys think would work for the .5hp m head mill for the generator, i just bought one and thought it would work. Thank you -Mike
What caused the generator to be the first choice over a VFD?
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Old 10-02-2014, 09:21:09 PM
Radiomike Radiomike is offline
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Default Re: 120v single phase motor turning 3 phase generator

Grif has given a sensible option, a variable frequency drive. These enable you to change speed, have a soft start and lots more for about $300.

If you wish to go ahead with the alternator option, lets have some more details of the motor on the milling machine. It may have a NEMA class on it giving details of the start torque and current, usually a letter A, B, C or D.

The rating of the generator you have, and the excitation type, quadrature winding with capacitor, rotating rectifier or slip-rings. What is the voltage regulator?

With a three phase alternator you have the option of reduced voltage starting if you can adjust the voltage. This will reduce the current needed, but reduce the torque as well. Does the alternator voltage match the motor, as often they can be configured in star or delta.

Mike
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Old 10-02-2014, 10:58:26 PM
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Default Re: 120v single phase motor turning 3 phase generator

Quote:
Originally Posted by gibbykart View Post
Well maybe i should Check to see what you guys think would work for the .5hp m head mill for the generator, i just bought one and thought it would work, the company said i can exchange for bigger or smaller at anytime, can anyone tell me what size single ph motor they would recommend to use with the indicated 3 phase gen when someone says what they would recommend for that? Thank you -Mike
I'd go with a 1.5 or 2 kW alternator, 2-3 HP motor. Maybe smaller if you're OK with the risk of it not plug reversing.

As Grif mentions, a solid-state variable frequency drive is the modern practical means to run small 3-phase motors. But since you specifically mentioned you wanted to run a 3-phase generator with a single phase motor, and that'd work fine, I'm not going to try to talk you out of that approach. (Although I put a VFD on my mill and couldn't be happier. To me even a rotary phase converter would be preferable over the setup you're asking about, but it's your choice...)

Yes - you'll get 58 Hz instead of 60 Hz. So what? It'll still work just fine...

If you have no idea what we mean when we recommend a VFD, do some googling. For about $200 you can have a variable speed set-up. Hooking it up might be an adventure, but the end result is nice...

Here's an example VFD:

http://www.factorymation.com/Product...V-2001-H1.html
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Old 10-02-2014, 11:24:04 PM
dkamp dkamp is offline
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Default Re: 120v single phase motor turning 3 phase generator

Or a really silly suggestion...

I took the Bridgeport motor off my M-head, and used a single-phase 3/4hp C-face motor with a 1/4" plate cut to mate the two...

A 3/4hp motor is well more than enough for the M-head... Between the M's spindle, and the lack of backgear and limited belt traction, the M-head won't transmit much power... fine for patternmaking with softwoods... going through the process of motor-generating 3-phase is rather arduous considering the result.
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Old 10-03-2014, 05:29:03 AM
ChipTosser ChipTosser is offline
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Default Re: 120v single phase motor turning 3 phase generator

An other option, If you want to make it simple, look up (Phazpak.com)
This is the simplest set up that you can do. That is if you want to go that way.
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Old 10-03-2014, 01:09:51 PM
grif grif is offline
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Default Re: 120v single phase motor turning 3 phase generator

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Originally Posted by chiptosser View Post
An other option, If you want to make it simple, look up (Phazpak.com)
This is the simplest set up that you can do. That is if you want to go that way.
I looked at their site. Couldn't decide if the standard model was a real single to three phase converter, or if it was just taking advantage of the machine tools existing 3 phase motor to treat it like a rotary phase converter, and just take power off the output shaft.
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Old 10-03-2014, 09:08:49 PM
ChipTosser ChipTosser is offline
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Thumbs up Re: 120v single phase motor turning 3 phase generator

Wire the unit in just as shown. 220 single phase with the unit wired to the third leg, with the run capacitors for the motor size. Turn the power on, your up and running.
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Old 10-04-2014, 06:57:45 AM
steve mallette steve mallette is offline
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Default Re: 120v single phase motor turning 3 phase generator

I would agree with Jim Mc a VFD is the smart way to go. It's cheaper ,easier ,more funcional and above all easier to install and keep going.. (YMMV)
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Old 10-04-2014, 10:53:14 AM
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Default Re: 120v single phase motor turning 3 phase generator

The VFD would be easier for you and me, but it does depend on a guy's skill set. Adding a VFD involves a bit of electreical-related work, reading a (poorly written) manual, and setting up a dozen or so key settings in the (cryptic) VFD menus...
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Old 10-04-2014, 12:00:37 PM
steve mallette steve mallette is offline
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Default Re: 120v single phase motor turning 3 phase generator

You can also add a remote (pendant) pot and controll speed at the machine... FWIW
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