Converting a 3-phase 230v motor to single phase 120v

Discussion in 'The Projects Forum' started by tonyfranciozi, Jul 25, 2011.

  1. tonyfranciozi

    tonyfranciozi Thread Starter New Member

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    Hi all,

    First let me say, excellent forum! This is my first post but I've been lurking for a while now.

    Ok, I have an industrial sewing machine from the 1930s that runs on a 1/3 horsepower 3 phase 210/230v AC motor. I'd like to run it on single phase standard 120v. I was looking into building a static phase converter but, from what I understand, that would reduce the motor's power by a third and could lead to overheating and eventually shorten the life of the motor.

    My question is, what is the feasibility of rewinding the motor to run on single phase 120v power? I do have Rosenberg's book on motor repair and rewinding, but I'd like to get more advice on the matter.

    Thanks for any help you can provide!
  2. strantor

    strantor Well-Known Member

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    (disclaimer: I don't know 100% what I'm talking about)

    semi-educated guess: I don't think it's possible. The fins where the windings go into the stator would probably be set up in a configuration divisible by 3 for the 3 phases. It probably would not work for a configuration where the windings need to be divisible by 2.

    There are "3 phase converters out there" which is basically a single phase motor coupled to a 3 phase generator; I've heard works and sounds feasible but never actually seen one.

    Probably best to get a new motor IMO
  3. #12

    #12 AAC Fanatic!

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    Could you post a diagram of a "static phase converter" just for my own education?

    I suggest a professional motor winding shop could tell you about feasability, maybe for free.

    I've seen single phase to 3 phase converters of the motor/generator type. They work wonderfully, but expensive and have moving parts to wear out. There would be less number of moving parts in a correctly wired motor you would buy. I bought a 1/4 hp motor for $65 last week. For this job, I'd be buying a motor in a New York minute.

    Still, if you want to learn about winding motors, that's a good enough reason to do it yourself.
  4. shortbus

    shortbus Senior Member

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    Are you positive the motor is actually three phase? If it is a variable speed sewing machine motor, a lot of them are actually a DC motor and VFD(variable frequency drive). Takes in three phase rectifies it to DC and drives the motor. Some of them can be used on single phase 220V by just using two of the input lugs.

    What is the make and model of the motor?
  5. strantor

    strantor Well-Known Member

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    did they have that technology in the 30's?
    shortbus and #12 like this.
  6. nuckollsr

    nuckollsr New Member

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    There are passive-static single-phase to 3-phase converters. Suggest you go to http://freepatentsonline.com and sign up for a free account. Then look up patent numbers 4777421, 4484125, 3673480 for a tip-of-the-iceberg peek at various approaches to your task.

    You may also wish to avail yourself of offers for plans to build single-to-three-phase converters. One example: http://tinyurl.com/3r3lbj5

    o wis The choices fall into two classes. A rotary converter (teamed single and three phase motors) will be the most efficient and least sensitive to actual load as long as it's large enough. A static capacitor/inductor network (also mentioned in the plans) is probably the best approach . . . but these are not as efficient. They'll choke off about 30% of your motor's output capability leaving you with a 1/4 horse motor (which might be sufficient to your needs).
  7. tonyfranciozi

    tonyfranciozi Thread Starter New Member

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    Here is a photo of the specs plate pinned to the motor's case. You can't see it in the photo but it specifically says AC.

    I'm looking in Rosenberg's book now and the only difference I can see between a three phase and single phase, besides the way they are wound, is the centrifugal switch that shuts off the starter winding of the single phase when the rotor reaches speed. I might be able to attach such a switch to my current rotor?

    The only reason I hesitate to get a new motor is because this is the original motor that came with the machine. Well, that and I've always wanted to rewind a motor but never had a decent excuse to!

    I don't have a diagram of a static converter, but I was reading about them here: http://www.metalwebnews.com/howto/phase-converter/phase-converter.html

    Attached Files:

  8. strantor

    strantor Well-Known Member

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    There are different types of motors even within the single phase category. not all of them use a centrifugal switch with starting cap. some use a run cap.
  9. tonyfranciozi

    tonyfranciozi Thread Starter New Member

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    So the motor could start without a centrifugal switch? Would the run capacitator connect to the rotor, or just the stator?

    I guess what I'm getting at is, could I do this without messing with the rotor at all? I don't want to throw the rotor off balance if at all possible.

    I'm really not worried about losing a third of the power, the machine could certainly run on 1/4 HP. My only worry would be overheating.
  10. tonyfranciozi

    tonyfranciozi Thread Starter New Member

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    Now I'm thinking that I could scrap the centrifugal switch altogether and just use a start-and-run capacitor. Can anyone see a reason why this wouldn't work?
  11. CDRIVE

    CDRIVE Senior Member

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    Since VFDs have become affordable Static and Rotary converters are becoming far less common. With one of these you can make that three phase do things they never dreamed of when they made it.

    http://www.automationdirect.com/adc...essionid=5e304bb3854bb7cf2b0b1c15307b525d7b26

    My Dad was a machinist and worked mosts of his life in the industrial sewing machine industry. I would appreciate it very much if you posted a picture of your machine...
    Last edited: Jul 25, 2011
    strantor likes this.
  12. strantor

    strantor Well-Known Member

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    http://www.pumped101.com/singlephasemotors.pdf
    page 5:
    read down further from page 5 where it starts to talk about capacitor run motors
  13. strantor

    strantor Well-Known Member

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    your link is broke, but, yes I agree. There are VFDs out there that will take single phase and output 3 phase, with speed & torque control, and be an economical solution. I can't believe I didn't think of that. VFDs are my "thing" DOH!
  14. CDRIVE

    CDRIVE Senior Member

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  15. strantor

    strantor Well-Known Member

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    that GS1-10P5 looks like the ticket!

    a lot more flexibility than any other option, and probably cheaper than any other option also.

    Just remember that, being from 1930, your motor is not inverter duty rated, so it will likely eventually fail due to the abuse from the inverter. When it fails, just have it rewound for inverter duty. it will probably need to be rewound soon anyway (if not already)
  16. CDRIVE

    CDRIVE Senior Member

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    I've always been curious about what they do differently now that makes current 3PH motors inverter compatible. Anyone got a definitive?
  17. strantor

    strantor Well-Known Member

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    better bearings and insulation. better cooling

    I've read much better writeups on the topic, but this is all i can find right now;
    http://motors.automationdirect.com/Information/faq.html
  18. tonyfranciozi

    tonyfranciozi Thread Starter New Member

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    CDRIVE and strantor, thanks for all the info, I guess a VFD is probably my best bet. I'll post pics of the machine tonight after work.

    I just want to throw one more possibility out there before picking up an inverter. Would it be possible to start the motor on the starting and running windings and then shut off the running winding manually with a seperate switch when the motor reaches speed?
  19. CDRIVE

    CDRIVE Senior Member

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    No, because there is no start winding on 3PH motors.
  20. tonyfranciozi

    tonyfranciozi Thread Starter New Member

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    Right, but if I were to rewind the motor as though it were a single phase with a starting and running winding would it be possible?
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