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Thread: Open frame induction motor for cheap, would you go for it?

  1. #1
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    Open frame induction motor for cheap, would you go for it?

    I got a tip for a 2.2 or maybe 2.6kw open frame 3-phase induction motor (I got 3ph so I can run it). It's a really old model, pre-war (that is ww2) most likely, not sure if it works, the man who sounds like an old man over the phone, said his father tested it and it worked then, whenever that might've been... I could get it for scrap money, 10-15 euros I might be willing to offer, he's gonna hook it up and test it so we can see.

    I was told it should be a forever kind of motor by the guy who tipped me about it, old solid design, just keep replacing bearings until heat death of universe, assuming the windings aren't broken or burnt.

    Thing is I would use it in my workshop which is a dusty enivroment, I'd put it on my jointer/planer. Would you guys put a non sealed motor in a woodworking enviroment?

  2. #2
    Quote Originally Posted by Dennis Aspö View Post
    I got a tip for a 2.2 or maybe 2.6kw open frame 3-phase induction motor (I got 3ph so I can run it). It's a really old model, pre-war (that is ww2) most likely, not sure if it works, the man who sounds like an old man over the phone, said his father tested it and it worked then, whenever that might've been... I could get it for scrap money, 10-15 euros I might be willing to offer, he's gonna hook it up and test it so we can see.

    I was told it should be a forever kind of motor by the guy who tipped me about it, old solid design, just keep replacing bearings until heat death of universe, assuming the windings aren't broken or burnt.

    Thing is I would use it in my workshop which is a dusty enivroment, I'd put it on my jointer/planer. Would you guys put a non sealed motor in a woodworking enviroment?

    For that price, yeah I'd use it. Maybe build a frame around it, covered in gauze or other type of filter material that lets heat escape, then just vacuum it occasionally.

    FWIW, my Delta 14" band saw came from the dealer with a 2 HP open frame motor. This was a supposed "upgrade" from the stock 1.5 HP, and at the time it never even dawned on me to check the motor type. Well, it's been run, fairly part-time, for ten years, and everything still seems fine. Very little dust actually gets into the closed chamber when the motor sits.
    -----------------------

    I always thought it might be possible to add some cooling fins to my motor's housing, either by brazing or simply with JB Weld, then seal the openings and add a large fan at the rear. Since I have no real need, there was no point in trying this, but you could give it a go, for that price. Of course, the motor still wouldn't have intenal circulation vanes, so you'd have to monitor the heat carefully, for a while.
    Last edited by Allan Speers; 05-15-2015 at 4:53 AM.

  3. #3
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    I'd get it just because it's cool. I love old motors. If it was single phase it would be troublesome because the starting switches get fouled up so easily. But with an open 3 phase motor you'd just have to remember to blow it out pretty regularly.

  4. #4
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    Got it home now, it's incredibly heavy! For a 2.2kw motor it weighs more than my 4kw one, but it spins around beatifully and incredibly silently. I think this will be a fine motor indeed. I want to restore and paint it, I think.


    It is open but it does have a fan:



  5. #5
    That kinda' looks like one of those old replusion-induction motors. If so, then nice score!

  6. #6
    Be cautious with any old electrical machine.
    The wire insulation is what breaks down and can cause arcing. Wood dust+spark = fire.
    Look for cracks in the lead wires.
    You might want to have the motor insulation checked using a megger.

    Motors this age are over designed and often do run forever.
    The nice thing about those old motors is they run cooler at rated power. They are also not as electrically efficient.
    Sorry to be such a downer.

  7. #7
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    Don't have a megger but it ran for several minutes without tripping the GFCI which an earlier motor of mine did after 10 seconds every time, when it had bad windings. It really exudes a higher build quality than my more modern sealed motors.

  8. #8
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    Quote Originally Posted by Allan Speers View Post
    That kinda' looks like one of those old replusion-induction motors. If so, then nice score!
    I think that is some kinda 1-phase starting switch isn't it? This is just a plain old 3-phase motor.

  9. #9
    Quote Originally Posted by Dennis Aspö View Post
    I think that is some kinda 1-phase starting switch isn't it? This is just a plain old 3-phase motor.

    Good question. The "repulsion-start" part only has to do with a ring of brushes that are used to boost the torque of the motor when starting. As the motor reaches maybe 1/2 speed (I forget the exact percentage) that ring lifts away via centrifugal force. I don't THINK this precludes 3-ph motors, but I really don't know.

    You'd know instantly if you open it up, which of course you have to anyway, to check the insulation & bearings. (It probably needs to be cleaned & re-greased. - and change "probably" to "almost definitely." )

  10. #10
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    I suppose it doesn't but I can't see a reason for it, a 3ph motor has lots of starting torque, seems to me the point of such a repulsion system is to give a 1ph motor the same starting torque as a 3ph one.

    The motor bearings move better than my other more modern motors which I've considered to be in fine shape up until this point. But I will have a basic and careful disassembly and see if I can get some new grease in the bearings.

  11. #11
    Quote Originally Posted by Allan Speers View Post
    That kinda' looks like one of those old replusion-induction motors. If so, then nice score!
    If I remember my motor theory correctly, replusion-induction motors have a higher starting torque than a regular induction motor but once they are up to speed, the power is essentially the same as a standard induction motor. Since most of our woodworking machines start unloaded there's no real advantage to a replusion-induction motor in woodworking.

    Also, if I remember correctly, replusion-induction motors are single phase motors, not 3-phase motors.

    The BIG disadvantage of a replusion-induction motor is the brushes - which wear out and require periodic maintenance. Replusion-induction motors are not used in any modern equipment, to my knowledge.

    While many older motors were well built, the materials (such as insulation) available to the designers were not as good as modern materials. Because the insulation was often thicker than modern insulation, the older motors are often physically larger than modern motors. Also, many did not have sealed bearings and require periodic lubrication.

    It's hard to beat a good quality modern induction motor.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  12. #12
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    Some pictures of it taken apart, it was much easier to disassemble than any modern motor I've worked on.

    Back lid off, some rust on the rotor:


    Windings are very dusty


    Look fine from the other side:


    Front lid removed:


    A closer look in between:




    A look at the bearing:

  13. #13
    That is really a neat motor. If that was made today, it would be a "spare no expense" design. Back then, that is how they did things.

    If you think of it, post a better pic of the cleaned-up plate.

  14. #14
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    I haven't got a pic but I was able to read the one I got and it says:

    Code:
    ASEA
    MOT 3 	~ 	50
    MKE 12 	N 	1160467
    2.2	kW	3 hk
    		1420 		r/m
    380	v	Delta		4.8A
    Usually more modern motors are 220V delta for norweigan 3-phase or similar, or Star for the usual 380/400V here. Interesting to see one with only the one voltage.

  15. #15
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    Nice photos too. You seem to have more than one skill.
    NOW you tell me...

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