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  1. #11
    Very interesting John, Just goes to show with knowledge and patience a lot can be achieved ..Clive

  2. #12
    Brilliant, well done. I don,t suppose that you want to rewind my HF (1000hz, 55volt) to 400hz 230volt), for a (small) bag of gold of course. This is a serious enquiry as I too have been told that it is not possible. G.

  3. #13
    Quote Originally Posted by GEOFFREY View Post
    I don,t suppose that you want to rewind my HF (1000hz, 55volt) to 400hz 230volt), for a (small) bag of gold of course. This is a serious inquiry as I too have been told that it is not possible. G.
    Sorry but modifying some one else's motor would be a bit scary , I persevered with mine mostly because I was told it's not possible and I could see no reason that it could not be done, just a matter of finding the correct info, I have spent a lifetime solving engineering problems, many of which were not possible.

    There are motor design programs out there but they are very expensive, need to find a friendly face in one of the universities. I tried a couple of re-winders for info but they really don't want to know about anything non standard.

    Modifying an existing motor should not be too difficult if you accept that the manufacturer got it right with respect to flux densities in the stator (ampere turns in old money).

    This something I found somewhere on the net.

    Rewinding for a change in voltage

    If a 220 volt motor is to be rewound to operate on 440 volts, use twice as many turns on each coil and one-half the circular-mills area of wire. In other words, if 40 turns of NO. 17 wire were used on the original motor, 80 turns of NO. 20 should be used on the new motor

    Some motors rated for 230 volts will not handle the load on 208 volts if loaded to the maximum. The turns must be reduced to the ratio of the voltage change. As an example, 230-volt motor has 40 turns: 230/208 = 1.1, 40 turns/1.1 = 36 turns. If there is enough room, the next larger wire size should be used. An easy way to determine whether there is enough room is to cut the required number of of lengths of wire of this size and fit then into the slot.

    Changes for New frequency

    There are two ways to convert these motors; one keeps the same horsepower for the new speed, and the other keeps the same torque for the new speed (more horsepower). For the same horsepower, use the following formula: old turns*Sqrt(old Hz / new Hz) = new turns. If you want the same torque then it is: old turns*old Hz/new Hz = new turns.

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  5. #14
    Quote Originally Posted by johnsattuk View Post
    There are motor design programs out there but they are very expensive
    Here's a free one:
    https://www.emetor.com/
    Although lately I've been using this one as it's on the university computers.

    Anyway, Geoffrey, have you got a picture of the stator inside your motor? I'd be interested in rewinding it / working out how for you. Who told you that it wasn't possible and what reason did they give?
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  6. #15
    Quote Originally Posted by Jonathan View Post
    Here's a free one:
    https://www.emetor.com/
    Although lately I've been using this one as it's on the university computers.
    I did find and play with emetor and also Koil, and some demo versions of others, but really my only requirement was no of turns per slot and I did not find that these gave me that info.

    I originally tried the forum in the hope that some kind soul would help with some positive info.

    It is highly unlikely that I will wind another motor, this was a just a whim that became a challenge.

  7. #16
    Quote Originally Posted by Jonathan View Post
    Here's a free one:
    https://www.emetor.com/
    Although lately I've been using this one as it's on the university computers.

    Anyway, Geoffrey, have you got a picture of the stator inside your motor? I'd be interested in rewinding it / working out how for you. Who told you that it wasn't possible and what reason did they give?
    Thanks for your reply and offer Jonathan. I do not have any pictures of the internals of my spindle as I have never thought about dismantling it. I have a couple of these spindles which I love to use because of the air release collet chuck and work around the fact that I am limited to 3.172mm shank tools. As I have a "spare" spindle I would be happy to take a chance that it does not work if you are prepared to try. The impossible comment came from various commercial rewinders and I had very little faith in that I believe that nothing is impossible!!! Perhaps a little difficult sometimes. The most logical comment came from one rewinder who said that it would be difficult on a small diameter spindle to use the heavier duty wire necessary to change. These spindles are lovely (ex pcb machine), but I only have one HF inverter and I would like to get one running on a standard 400hz inverter as I have started to strip down another machine which has a cutting area of 540x600mm. G.

    I apologise if I seem to be hi-jacking this thread, but I did start a somewhat similar thread about my spindle and had no response. G.
    Last edited by GEOFFREY; 11-04-2014 at 02:43 PM. Reason: apologies

  8. #17
    Quote Originally Posted by GEOFFREY View Post
    The most logical comment came from one rewinder who said that it would be difficult on a small diameter spindle to use the heavier duty wire necessary to change.
    Not sure it was a very logical comment, I would expect the requirement would be for more turns of a smaller dia wire.

  9. #18
    Impressive ! good job (Edit: The rewind I mean)
    Last edited by EddyCurrent; 11-04-2014 at 03:12 PM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  10. #19
    Oops!! That could be my misinterpretation. Perhaps he meant not enough room to get the turns in. Anyway, they said it would be impossible - I guess they were just not interested. G.

  11. #20
    Quote Originally Posted by GEOFFREY View Post
    Perhaps he meant not enough room to get the turns in. Anyway, they said it would be impossible - I guess they were just not interested. G.
    I think you guess correctly, getting the turns in is not generally a problem, once you know the turns you have to decide on the wire dia that will fill the slots as much as possible, bigger is better but it depends on the practicalities of getting them in. It may be that the number of turns required reduces the dia of the wire enough to limit the current, and thus the power of the motor.

    What is the current rating of the existing motors, may be cheaper to get a VFD with enough amps to drive them, you would be able to program it for the volts.

    Be interesting to see Jonathan's winding solution.
    Last edited by johnsattuk; 11-04-2014 at 04:26 PM. Reason: spelling

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