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  1. #1
    Join Date
    Dec 2005
    Location
    South Australia
    Posts
    1,656

    Default Can I upgrade to a VFD

    Hi,
    Some advice from the cleaver people please I have a AlG 50 G metal lathe (9X20) purchased from Hercus at least 25 years ago, apart from a few (China cut cost) things it has served me well and still will unless I win the lottery
    The one thing thing thing is really a PITA is every time I need to change speed I have faff around with belts and gears etc.
    Is there any reason why I could not replace the motor with a 3ph unit (larger hp ) and a VFD

  2. #2
    Join Date
    Oct 2011
    Location
    Norwood-ish, Adelaide
    Age
    59
    Posts
    6,542

    Default

    It varies depending on the view of the person stating it, but typically a VFD will manage a 3:1 or 4:1 speed ratio. Because of that you will still need some gears in the power train, as a lathe typically has a far greater range of speeds. If you are only working on a limited range of diameters and don't thread cut, you might be able to do VFD only.

    Michael

  3. #3
    Join Date
    Jun 2005
    Location
    Helensburgh
    Posts
    618

    Default

    VFD's offer reduced power outputs at lower RPM unless they have Vector control. We use and supply Powtran and have done for about 10 years and originally they did not have Vector control from memory. I have a gearhead drill with a Powtran on it and rarely use any of the mechanical speed change controls but of course a lathe is a different kettle of fish altogether. PM me if you want help sourcing a VFD, we offer full factory support from the manufacturer and full programming advise.
    CHRIS

  4. #4
    BobL is offline Member: Blue and white apron brigade
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    7,183

    Default

    If you currently have a 1HP motor and replace it with another 1HP and a conventional (non-vector drive) VFD you will only get full power when running the motor between 50 and about 125 Hz (that a full power speed range of 2.5:1

    If you double the motor power it will generate get 1HP from 25Hz up to ~125Hz, or a speed range of 5:1

    If you use a vector drive VFD and a double power motor you should be able to get about 10:1 at full power.
    One caveat is, below about 15-20Hx is the motor is used at full power for long periods it may overheat.

    When heat forming my Bell mouth hoods on my WW lathe I run the VFD at round 8Hz during the forming process. Mostly it is free running but while the hoods are being made (~5 minutes) the high tailstock pressure requires the motor to output about 75% of its max power at that frequency. Once they hoods are formed I up the speed to about 20Hz for about a minute which helps cool the formed hoods down quickly. After making about a dozen hoods I just feel the motor getting warm.

    I still swap the gears but only very occasionally.

  5. #5
    Join Date
    Dec 2005
    Location
    South Australia
    Posts
    1,656

    Default

    Thanks now I need to put my thinking cap on.

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