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motor speed controler

Discussion in 'General Electronics' started by robb, Jul 22, 2007.

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  1. robb

    robb Guest

    i have a sewing machine motor controler (wired in series with motor) that
    uses a"carbon pile element" where pressure on the pile causes decrease
    and more current to flow and at some pressure point a short by passes the
    carbon pile

    controler is rated at 95-145 volts and 0.7 amps

    now someone has claimed no troubles using the controller with a 120v - 1 amp

    is this true ? why or why not

    i thought the motor , rated 1 amp, would try to draw more current than the
    controller was rated for and of course overheat etc

    any help greatly appreciated
  2. Well, it probably does, and the speed control is probably getting hotter
    than before. But there is a safety margin built in so it hasn't melted
    down just yet.

    Or, just because the motor says 1 A doesn't necessarily mean it draws
    1 A except under heavy load.

    Has he measured the current?

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  3. robb

    robb Guest

    ( this mesg was crossposted and multi-posted for which i appoligize to those
    that care)

    Thanks for help Sam

    no the curent has not been measured,

    the question is based on the issue of a failed original 0.5 amp rated motor
    being replaced with a newer 1.0 amp rated motor and wether that is such a
    good idea given rating on the controler.

    so the original safety control seemed to be factored with a 0.5 amp motor
    and 0.7 amp controler ?

    thanks again for reply
  4. James Sweet

    James Sweet Guest

    The current draw relates more to the load on the motor than the size of the
    motor. It will probably be fine though, just keep an eye on the temperature.
  5. robb

    robb Guest

    well that makes me wonder then because the most load the motor probably gets
    is at startup

    because the motor has a ~1/2" diameter pully and the machine has a ~4"
    diameter pully (which has a heavy flywheel ). The pullies connected with a
    big rubber O-ring belt. Getting the machine going is a big tug on motor...
    then when it is going it rarely gets any load of significance as fly wheel
    helps drive needles through the work when resistance comes

    Plus one rarely runs machine for extended periods it is usually stop and go
    where machine runs for 20-30 seconds stops and repeat

    thanks everyone for help,
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