Results 1 to 7 of 7
  1. #1
    david n's Avatar
    david n is offline Titanium
    Join Date
    Apr 2007
    Location
    Pillager, MN
    Posts
    3,550

    Default Variable speed 1/4 hp motor

    What would be the best and cheapest way to make a 1/4hp single phase motor variable speed? And I stress cheapest! TIA

  2. #2
    MXtras is offline Aluminum
    Join Date
    Jul 2007
    Location
    Virginia, USA
    Posts
    59

    Default

    The only method I know of is with a VFD.

    What is the application?

    Scott

  3. #3
    Join Date
    Apr 2005
    Location
    Benton, IL USA
    Posts
    4,571

    Default

    make a 1/4hp single phase motor variable speed?
    That depends on the motor:

    If it's an AC induction motor, gears or pulleys would work, as would a variable speed gearbox.

    If it's an AC/DC universal (brush type) motor, a router speed control would do.

    If it's a DC permanent magnet motor, you'll need a PWM motor drive.

    To use a VFD, the motor must be three phase.

  4. #4
    Forrest Addy is online now Diamond
    Join Date
    Dec 2000
    Location
    Bremerton WA USA
    Posts
    9,306

    Default

    SIngle phase induction motors don't work with VFD's. Period.

    Your best bet for cheap is a spring loaded variable speeed pulley with the motor on a swing mount. You can get about a 3:1 speed variation from that. You can get about 7 to 1 with a two pulley V/S drive.

    Here's a source:

    http://www.lovejoy-inc.com/content.aspx?id=356

  5. #5
    Pierce Butler is offline Hot Rolled
    Join Date
    Jun 2007
    Location
    Texas
    Posts
    728

    Default

    Cheapest way I know of is to pick up a 3 phase 1/4 ph motor for free and add a VFD. Depending on the VFD you get, a new VFD will cost between $99 and $120. $99 for the 1/4 hp VFD and $120 for the 1hp version. You will have all the variable speed you need.

  6. #6
    Join Date
    Apr 2005
    Location
    Benton, IL USA
    Posts
    4,571

    Default

    Your best bet for cheap is a spring loaded variable speeed pulley
    Nice link, Forrest

    I've used Browning adjustable pitch sheaves, which are similar because the pitch diameter is variable.



    Screw in the threaded side to increase PD, screw it out to decrease PD. The motor still has to be on a hinged or spring loaded mount.

    Barry Milton

  7. #7
    minder is offline Stainless
    Join Date
    Nov 2004
    Location
    Canada
    Posts
    1,765

    Default

    If you want to control an existing 1ph motor, then as mentioned already, VFD is out,
    I would either look at 3ph motor and VFD, or get a surplus 90v DC motor and SCR controller, these are relatively cheap, you do not need PWM.
    120v or 240v can be had on ebay for ~$25.00.
    These run direct of the 120v supply.
    If the motor has a tach, you get the bonus of closer speed control, as the Baldor or KB SCR drives will run with or without tach.
    If you need extremely high rpm, then a Universal motor and TRIAC (router) controller would do it.
    Minder.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •