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Can moters be run slower with less voltage (brush types)

Discussion in 'Electronic Repair' started by davidlaska, Sep 18, 2006.

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  1. davidlaska

    davidlaska Guest

    I heard power tools run on long cords go bad sooner. I assume because
    of the voltage drop the motor runs slower. I am thinking that the
    voltage drop is not a direct factor but slower speeds means less
    airflow since they all have a fan on the shaft (except pass through
    vacuums unless heavy duty. I remember in the seventies sears had a
    vacuum that had two speeds. But I think it was controlled by the entry
    point of the wire in motor, not a device that is like a dimmer made for
    brush motors. I saw one on a centrifuge and after market for routers.

    I am asking if lack of air flow from lower speeds due to voltage drops
    damage power tools (skilsaw and such)
  2. I wouldn't put much stock in it, but shorter, heavier cords are a good idea.
    I'd be more concerned about low voltage at the outlets. Maybe your tools are
    just cheap?
  3. davidlaska

    davidlaska Guest

    I only hear about power tools like skill saws can be damaged. Never
    had a tool go bad. I thought these motors can run at any speed if cool.
  4. davidlaska

    davidlaska Guest

    I forgot to say that cheap tools do break quick, stuff from China, I am
    not blaming them though, they deliver what the market will take.

    What I thinks I am really asking is a long cord voltage drop similar to
    after-market devices that slow down motors like a router?
  5. James Sweet

    James Sweet Guest

    Similar, you're limiting the current though rather than effectively
    using PWM so you'll get less torque with voltage drop than with a speed
    controller, the motor shouldn't heat up more than usual though.

    Induction motors on the other hand will overheat if the voltage drops.
    They're constant power devices and lower voltage will cause higher
    current to be drawn to compensate, higher current = more heat.
  6. Guest

    Dont believe everything. The only motors so affected are induction
    motors, which are at times found in stationary tools but not hand

    Reducing V reduces both power diss and airflow, and temp stays roughly
    constant over a wide speed range.

  7. davidlaska

    davidlaska Guest

    Thankyou: it is popular among carpenters but they can continue thinking
    that and get the large cords.
  8. davidlaska

    davidlaska Guest

    Thankyou: it is popular among carpenters but they can continue thinking
    that and get the large cords. I do not want to explain it unless asked.
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