how to slow down an electric motor

Discussion in 'General Electronics Chat' started by daveydo, Nov 6, 2015.

  1. daveydo

    Thread Starter New Member

    Nov 5, 2015
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    0
    Power supply input: 100 to 240 volts, 50 to 60Hz, 1.5 Amps; Output: 15 volts, 4 Amps. Horsepower and torque: 0.5 HP, 40 in-lbs, 300RPM. Comes with a 9-foot US cord.
    I have this motor on a device and it does have a thumb turn roller, what i call a rheostat device, that does control the speed, but at the onset of activation of it, at its slowest activation of the motor via the rheostat, the motor turns too fast. How can I slow it down?
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,118
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    What do you mean the output is 15v? Is there some sort of transformer in between the mains power and the motor? Is there also a rectifier?

    Any possibility to use a gearbox?
     
  3. Aleph(0)

    Member

    Mar 14, 2015
    343
    323
    If motor induction type, control needs be inverter drive (like VFD). If motor brush and com type control can be rheostat which means variable resistor but way inefficient! Should use pwm or phase control! Slow as 300 rpm means gearmotor or sophisticated driver for dc motor.

    With poor designed phase controller start setting and av higher than lowest setting so plz try turning control back down just after motor start:) Also vfds and dc motor controllers are cheap to buy and easy to design and build so you're spoiled for choice of solutions to trouble:D
     
    Last edited: Nov 6, 2015
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  4. TheButtonThief

    Active Member

    Feb 26, 2011
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    Motor speed control? Easy, PWM.
     
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  5. Techno Tronix

    Member

    Jan 10, 2015
    140
    10
    If it's direct drive you can install a VFD (variable frequency drive control) - not real cheap. If belt driven, you can change the sheaves to slow down (increase driven sheave dia. or decrease driver diameter.
     
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  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Can we have a picture of this motor and its controller, where's the 15v coming from?
     
  7. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Actually, VFDs are less expensive than you may think -- for instance, a unit applicable through 3 HP may be purchased new for Ca. $500 (USD) --- On the other hand, should the motor in question be of commutated construction, I concur with posts #3 and #4 in that a PWM based controller is the best solution where speed and torque regulation are required...

    best regards
    HP
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Or just over $100.00 if you want to go Chinese, (Huanyang).;)
    variable freq does not work well on 1ph induction motors, they tend to drop out of run on load at low rpm.
    I suspect it is DC?
    Max.
     
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  9. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    FWIW Shaded pole units seem to perform acceptably at low Freq/AV --- That said, I doubt the OP's 1/2 HP motor is of shaded pole construction:oops:

    Best regards
    HP
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Shaded pole motors are usually small/fractional motors, and in most cases are controlled with a simple phase angle (Triac) control, I don't recall ever seeing a VFD for one of these which I suspect would be un-economical to produce?.;)
    Max.
     
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  11. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    No doubt:) -- I was citing results from my own experiments with DIY VFDs and 'skeleton-frame' shaded pole motors (think turntable and Tektronix 'boat anchor scope' fan motors):D
     
    Last edited: Nov 7, 2015
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