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Need a new motor for South Bend

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  • #61
    Originally posted by J Tiers View Post
    ... I converted a single phase machine to 3 phase, and put in an RPC.... because it was a lot better as 3 phase. .
    Mind blown.
    But everyone makes the (their) world go round.

    -D
    DZER

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    • #62
      Originally posted by J Tiers View Post

      What evidence of stress and wear did you observe?
      Bent motor brackets. My 10K has the motor under the lathe headstock in the cabinet. Perhaps I should have taken some photos, but I didn't. It was just obvious that the sudden start of the relay-controlled motor arrangement was hard on the mechanism. Anyway, the soft start/stop imposed by the VFD is obvious on the lathe and on the Bridgeport. Ah, and the speed control using the VFD means that I don't have to change the step pullies as much on either the 10K or the Bridgeport. (Both are step-pully machines.) Anyway, IMHO the usefulness of the VFD and 3-phase motor is well worth the extra $$. Does anyone run a Bridgeport on a single phase motor? My South Bend 9C had a single phase motor, but the Bridgeport and the 10K both have 3-phase)
      -Mark

      The curse of having precise measuring tools is being able to actually see how imperfect everything is.

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      • #63
        Originally posted by Doozer View Post

        Mind blown.
        But everyone makes the (their) world go round.

        -D
        No reason to have your mind blown.... I knew I wanted more 3 phase machines, and it was an easy cheap way to do it. Arco RPC, for maybe a hundred bucks from a guy who replaced it with a bigger one, motor from Surplus Center $50, and all done.

        If I ever decide I really need variable speed, I will put a VFD on that machine. So far it is not worth the work, so I have not.
        CNC machines only go through the motions

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        • #64
          Those wiring diagrams are way over my head right now.

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          • #65
            The closer I looked at that home-made circuit, the worse it looked.

            Once a single phase induction motor gets up to speed, it might be able to run without the auxiliary winding, although probably at much reduced torque. And it would need a spin to get started.

            Capacitor start and capacitor run (PSC) motors depend on having a specific frequency and voltage to operate properly, although a range of perhaps 45-65 Hz might work. With a proper V/Hz VFD, a wider range should be possible, but the fixed capacitor size is a problem. It should be possible to program a custom designed VFD to provide the appropriate voltage and phase shift for the third winding over a range of frequencies.
            http://pauleschoen.com/pix/PM08_P76_P54.png
            Paul , P S Technology, Inc. and MrTibbs
            USA Maryland 21030

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            • #66
              Maybe I've been away from motors / controllers too long - I was thinking someone might consider recommending a permanent magnet DC motor and drive as a (slightly) less complicated way for the the OP to get continuously variable speed control and dead simple reversing.

              Before passing them to me, my father converted an SB 9, a Logan 9, a small vertical mill and 2 sizes of bench-top drill press all to DC motor/drive. For a not too capable/experienced hobbyist like myself, the continuous variability saves all kinds of crashes and disasters.

              A cursory search suggests places like Nebraska Surplus (and others) have fractional hp DC motors and drives for prices not too different from 3 phase. Still have to do a bit of moving belts from pulley to pulley if the required RPMs are significantly spaced - such moving from a 3" hole saw in the drill press to a 1/32 drill - but the middle ranges do most things for me, most of the time.

              Is DC out of favour for some reason I am overlooking?

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