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  1. #1
    Join Date
    Feb 2006
    Posts
    1187

    my 9x20 lathe motor runs slow

    Well after a 2 days of figuring out how to wire my 3/4 hp motor on my 9x20 lathe, I realized something still is not right. This motor replaces the 1/2 hp motor I had before(Grizzly nor Harbor Freight carry the 1/2 hp anymore). This motor is larger so now I need longer belts and I assume that I need to replace the cap.

    So my question is does a wrong sized capacitor make a motor run slow? Or is it possible I still don't have it wired correctly? I can go forward and reverse without smoke or burning smell so I figured I have wired right and I was thinking I probably need to replace the cap as Grizzly lists a different sized cap with their 3/4 hp motors.

  2. #2
    Join Date
    Feb 2006
    Posts
    1187
    What ya think Al?

  3. #3
    Join Date
    Dec 2003
    Posts
    24220
    Most of these motors are capacitor start only, once you have any kind of rpm the capacitor is out of circuit via the centrifugal switch, this just leaves the run winding across the supply.
    The capacitor should have come with the motor?
    Did you try connecting it direct to the supply, and bypass the rev. switch?
    Have you identified the two circuits, the run winding and the cap-start winding?
    Is the new motor dual voltage?
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  4. #4
    Join Date
    Feb 2006
    Posts
    1187
    Yes I believe its dual voltage as the schematic gives you 110 and 220 wiring options. And now I'm thinking its wired for 220 when I really want it to be 110, this would explain why its running slowly. And I haven't identified the two circuits , I'm going to try that tonite, just read up on how to identify them.

  5. #5
    Join Date
    Feb 2006
    Posts
    1187
    Ok switched some wires and now it runs up to speed , however I believe a new cap is in order as it starts slow and then it kicks in and you can hear the cap turn off. I also have it wired backwards(forward is reverse) but I,m gonna leave it, tired of switching wires. For now until I get a new cap I can only run it in low gear plus I need a new belt, thanks again for your help Al.

    All Hail Al !!!!!!!!!!!!!!!!!

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