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  1. #1
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    Default Repulsion - Induction motor, single phase, 5HP

    Some time ago I inherited an old Repulsion-Induction motor labelled for 200/400V from a relative. This is a big and heavy beast. I estimate it at 100kg (must weigh it one day for the fun of it). I can only just tip it over - not a hope of lifting it.
    It has reportedly "blown the heater" in its switch gear.
    Encouraged by my reading of RayG's Basics of Electrics, and some other reading, and a close look at the switch gear, I finally decided that my sawbench could do with some tweaking (I was cutting firewood today).
    So I cleaned this thing out after moving it out of it's storage "space" with my engine crane. I soon realised that the "heater" was just some sort of thermally operated circuit breaker (I think).
    Trying to figure out how the electrics in the motor worked was unfruitful in the process.
    However, I confirmed the connections and connected it in 400V mode to see if it had an earth leakage fault and if it ran to start with.
    It ran! .... and the lights didn't flicker or any fuses or RCDs blow.
    But what looked to me like a centrifugal device didn't move.
    Next test: 200V connection mode.
    It accelerated a lot faster but stilll nothing happening with the centrifugal thingi.
    So off came one of the end covers and I - only just - managed to slide and lift the armature out (at a guess 60kg).
    I then could see what the centrifugal gizmo was supposed to do: it was meant to push the 4 huge carbon brushes of the axial commutator, and they were stuck solid.
    On closer examination, I could see that they each had a complicated parallelogram mounting system which was 'frozen'. I cleaned this with some CRC and lubricated and exercised them a bit and they came quite free to move.
    A bit more internal cleaning and checking of insulation confirmed that all looked well and I reassembled the monster.
    Switching it back on, it accelerated and then with a loud 'smack' and big spark, it went into "stealth mode", running beautfully quiet in its massive oil bath and rotating bronze ring bearings. Just lovely
    Given that it has a 4-row B-section pulley, these might be 5 real old-fashioned horse power....
    I'll mount it on my sawbench (currently 3 modern light duty one-hand-lift-sized HP) next weekend and see how it goes. I'll measure the current draw under load once it's installed and see. The nameplate says 31A at 200V on full load (I have a 32A circuit in my shed).....

    So, if I understand it all correctly, this is sort of two motors in one: a commutated winding on the rotor (armature) which is in use with the induction windings as its fiels coils at start-up. Interestingly, the 4 big carbon brushes are all connected to gound and to each other. So the armature is exited only inductively. Once up to speed, the armature brushes get pushed off the commutator and then the motor runs in induction motor mode. Quite clever really. It is meant to prevent a huge start-up current if I read it right.

    Cheers,
    Joe

  2. #2
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    Default

    Hi Joe,

    Nice bit of detective work there..

    Rosenberg has a chapter on repulsion type motors, yours sounds like a repulsion start induction run, is it like this..



    Apologies for the poor scan, bit low on contrast..

    Regards
    Ray

  3. #3
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    Default

    Yes Ray, very much like it, although it's not a Wagner.
    This is my hand btw, not a child's hand.... it's about 16" diameter....
    Joe

  4. #4
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    Hi Joe,

    That's a real beauty! Should run a saw bench pretty well, just in time for winter firewood as well....

    I should make a slight correction to your original post, the Electrical Basics files are courtesy of GQ, I just uploaded them, so thank Greg next time you see him..

    Regards
    Ray

  5. #5
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    Yep, you are right, Ray, I forgot....
    Thanks Greg!
    Cheers,
    Joe

  6. #6
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    Just how many ways are there to skin a cat?
    Nice one Joe, even if I havent got my head around how it work yet.

    Stuart

  7. #7
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    Great job Joe, your story reminds me of the rebuild done by a member on PM IIRC who had an even older looking motor, smaller than yours I would think, possibly around 2 or 3 HP. I think that he may have had it rewound, but am not too sure on that now, but the "before" photos showed this motor covered with about 80 years of grime and dust, and the "after" photo showed this gleaming "Ferrari Red" motor with attention to detail, both inside and out, like that seen on a concours vintage cars. The paintwork looked immaculate, definitely much better that the usual motor rewinders job. As I recall, he was fitting it to some equally ancient machine tool in a similar state of restoration. Anyway well done with your treasure.

  8. #8
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    Default What would Bob do?

    The monster motor is now installed and tested in my firewood saw bench.
    Before I mounted it, it occurred to me that I would not be able to shift the sawbench ever again (because of the weight). A solution had to be considered.
    We agreed (wife, son and I) that it was not in a good position anyway. And we also thought that ideally it should be able to be used in two positions to suit cutting from a pile of logs or directly from the trailer.
    Once the weigth of the motor was added, the only feasable way I could think of was to mount it on rails!
    Some mental design around materials on hand dictated the outcome.
    Once it was all welded up, tracks levelled and backfilled, the sawbench still looked like a dangerous pile of rusty junk.
    So once at it, I decided to cut, fold and fit more reasonably fitting blade guards and fix all the faults I found with it over the past 20 years or more. All using other junk on hand od course.
    Now it did actually look like a proper saw bench! but something still wasn't quite right......

    Then it dawned on me: "what would Bob do?"

    He would say that it needed a nice lick of paint! Both to protect it from renewed return to rusty junk and to give it a 'shine'.

    The result is below.
    It still need the electrics done properly, a belt guard and a saw dust chute to keep the sawdust out of the very open-framed motor.
    The motor will shortly get a proper weather cover as well.

    Cheers,
    Joe

  9. #9
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    Hi Joe,

    That came up nicely, now that you've got some railway tracks down, you should extend the line up to the house, so you can load up the firewood and roll it all the way to the fireplace...

    Of course, you'll have to build a steam locomotive to pull the firewood wagons..

    Nice job. Just in time for winter too..

    Regards
    Ray

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    Steam locomotive!!!! Hell yeah.

    Phil

  11. #11
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    Hi Joe

    Came up great, must only just clear the shed.

    You'll have to sell tickets pretty cheap, even I'd walk that far

    Stuart

  12. #12
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    Ueee is offline Blacksmith, Cabinetmaker, Machinist, Messmaker
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    Quote Originally Posted by Stustoys View Post
    Hi Joe

    Came up great, must only just clear the shed.

    You'll have to sell tickets pretty cheap, even I'd walk that far

    Stuart
    I think he could sell the tickets at a pretty good price once he has removed the two things on the end of you legs with that monster.......

    Good job Joe,
    Just make sure its only wood it cuts! (unless your selling tickets of course)
    Did you make the saw entirely or was it one that was driven of a tractor's PTO originally?
    Love the belt guarding, just don't show an OHS officer.......

    Ewan

  13. #13
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    Default

    Thanks for the comments.
    Ray actually saw it close to its original state of returning to iron oxide last Wednesday....
    Ewan:
    yes, it was a homemade PTO driven saw. I inherited from a neighbour who moved into town about 25 or so years ago. We used it flat-belt driven off my 1951 Fordson E27N for a few years until I sold it (after my first back surgery, when I could no longer crank start it, and the saw was the only implement left in use).
    Since then it I fitted a 20" blade instread of the original 32". It has variously had 2x2HP motors fitted (running with a belt each onto the same spindle) a 3HP and a 1.5HP (same arrangement) and just the 3HP when the 1.5HP got wet one winter and seized one of its bearings (its now rebuilt and drives SIL's bandsaw).
    This 5HP motor is unstoppable with the current blade - I tried and eventually it slipped the belt
    Joe

  14. #14
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    Hi,

    That motor looks very similar to one I had 30 years ago.
    Mine was a 240V, 1 HP, made by Century & co, it was huge, it took 2 people to lift it. Oil bath bronze ring bearings, 4 carbon brushes on the axial commutator, that were all shorted together.
    Once up to speed, a centrifugal switch lifted the 4 brushes off of the commutator, and a metal ring was forced onto the commutator, shorting the windings, turning the armature into an induction motor.
    The position of the 4 carbon brushes could be changed by loosening a bolt on the commutator mount. By rotating the mount you changed the direction that the motor would start.
    This motor was off of a very old shoe makers sanding/buffing machine.
    The motor had a huge starting torque, the first time I started the motor, I didn't have it bolted down, and the motor just jumped up and rotated across the yard, thankfully that pulled the 240V leads off motor, otherwise it would have demolished the fence.

    Regards Steve.

  15. #15
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    Yes, Steve, this one is exactly as you describe it. Due to the massive weight and size of this one, it can safely be started sitting there and not jump up
    I moved the brush holder to change its rotation for the saw just as you described.
    Cheers,
    Joe

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