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Clue me in on this.

Discussion in 'Electronic Repair' started by Warren Weber, Jul 5, 2007.

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  1. Warren Weber

    Warren Weber Guest

    --
    Capacitor start motor. Starts and runs in either direction as it pleases.
    Capacitor good (replaced with others as test) 2 windings. Run winding across
    line voltage, Start winding across line voltage with capacitor in series.
    What determines rotating direction when starting?? This is on a small Delta
    9 inch bandsaw. Both windings ohm out OK.
     
  2. indago

    indago Guest

    070704 2133 - Warren Weber posted:
    The motor should start and run in only one direction. My first thoughts are
    that the starting relay in the motor is either stuck, or the contacts are
    dirty. You will probably have to take the end bell off the motor and check
    out this relay. It works on a centrifugal principal: as the motor speeds
    up, the relay opens and removes the capacitor and start windings from the
    circuit.
     
  3. Slight correction. A capacitor start motor may run in either direction
    but the winding used for starting should only start it in one direction
    with a given wiring arrangement. This is determined by the placement
    of the capacitor and the physical construction of the motor.

    --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
    Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
    +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
    | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

    Important: Anything sent to the email address in the message header above is
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  4. Charles

    Charles Guest

    Is there a centrifugal switch in series with the start circuit? If yes,
    then it is the relative phase of the two windings that determines the
    direction of rotation. To reverse this type of motor, swap ends on either
    winding (but not both). This is also true of split phase motors (no start
    capacitor but still have the centrifugal switch).

    I have seen motors of this type with open start circuits that will start in
    either direction with the slightest nudge ... of course, they have very low
    starting torque.
     
  5. Warren Weber

    Warren Weber Guest

     
  6. Warren Weber

    Warren Weber Guest

    NO start switch. ???
     
  7. Charles

    Charles Guest

    http://www.lmphotonics.com/single_phase_m.htm

    Capacitor start/run

    Hope this helps you but it doesn't seem to answer your problem. However,
    having properly identified the type of motor, you can Google for more info.
    Or, post again with the motor properly identified.
     
  8. See if there is any torque during starting. I bet there is none and
    little load, so it starts either direction at random. The circuit
    to the starting winding is not being energized or the start capacitor
    is open (but you said you checked this?).

    --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
    Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
    +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
    | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

    Important: Anything sent to the email address in the message header above is
    ignored unless my full name AND either lasers or electronics is included in the
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  9. James Sweet

    James Sweet Guest

    If there's no start switch, it's a permanent split capacitor, or PSC motor.
    Never seen one that would run in either direction without changing the
    wiring though. Normally you swap the phase of one winding to reverse.
     
  10. I had a machine with a reversable capacitor start 1 HP motor. I found
    that if you switched the direction without stopping the motor, the
    inertia of the machine would cause it to keep on running in the original
    direction despite the winding mismatch.

    I had a machine with a reversable capacitor start 1 HP motor. I found
    that if you switched the direction without stopping the motor, the
    inertia of the machine would cause it to keep on running in the original
    direction despite the winding mismatch.

    --
    Joe Leikhim K4SAT (this posting in DSB to placate the KOOKS)
    "The RFI-EMI-GUY"©

    "Treason doth never prosper: what's the reason?
    For if it prosper, none dare call it treason."

    "Follow The Money" ;-P
     
  11. Right, has to be an open start winding or something along those lines.
    The direction is determined by the physical winding placement.

    --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
    Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
    +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
    | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

    Important: Anything sent to the email address in the message header above is
    ignored unless my full name AND either lasers or electronics is included in the
    subject line. Or, you can contact me via the Feedback Form in the FAQs.
     
  12. Yes, because that probably has a centrifugal starting switch which
    disconnects the starting winding entirely when at normal speed. So, the
    direction changing switch has no effect until it goes down to below about
    75 percent of normal speed.

    --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
    Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
    +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
    | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

    Important: Anything sent to the email address in the message header above is
    ignored unless my full name AND either lasers or electronics is included in the
    subject line. Or, you can contact me via the Feedback Form in the FAQs.
     
  13. Warren Weber

    Warren Weber Guest

    Thanks for all of the replies. Just a cap start motor. 1 cap 2 windings. As
    shown on #5 that charles sent. Did ohm out per diagram. May be a shorted
    start winding. This is a band saw motor (Delta) Price on motor almost same
    as price of saw. (9 inch saw). Owner will replace saw. TIA. WW
     
  14. Makes sense

    Makes sense

    --
    Joe Leikhim K4SAT
    "The RFI-EMI-GUY"©

    "Treason doth never prosper: what's the reason?
    For if it prosper, none dare call it treason."

    "Follow The Money" ;-P
     
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