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Asking for a friend who is intending on setting up a one-off, custom-built appliance for a farm. He needs a motor and control scheme for "rotary impact cleaning". It should be:

  • Low-cost (insofar as that's possible)
  • Accuracy and efficiency do not matter whatsoever, direction doesn't really matter either
  • Three-phase is unavailable so he's stuck with 110VAC single-phase
  • Has rudimentary speed control - either continuous or multi-setting
  • Is "reasonably powerful", perhaps 500W
  • Can handle unpredictable mechanical load
  • Target RPM up to perhaps 300 RPM

Commonly-available used parts are preferred if possible, but new parts are not ruled out completely. Custom circuitry is fine if needed.

I've seen controllers for sale that convert a single-phase supply to a lines controlling a three-phase motor, and that's OK in principle, but these controllers were somewhat expensive.

My questions are:

  • What kind of control scheme (phase or inverter control, etc.) is appropriate here?
  • Are there any common types of appliances or automotive systems, etc. viable as used sources for such a system?
  • Failing used parts, what category of new parts should I be looking at - motors with integrated speed control, or a separate controller, etc.
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  • \$\begingroup\$ This is a matter of searching for what is available and comparing prices and specifications. Nothing that you have describes provides a reason for preferring one control scheme over another. \$\endgroup\$ – Charles Cowie Sep 1 '17 at 3:48
  • \$\begingroup\$ Hard to say without a target power in Watts or HP rating and expected RPM. \$\endgroup\$ – Jack Creasey Sep 1 '17 at 4:28
  • \$\begingroup\$ For cheap a treadmill DC motor, for better reliability a VFD and 3-phase motor, but it really depends on a lot of unstated factors. Something that runs 24/7 will have different needs for something that is rarely in motion, and as Jack says, HP and RPM and required start torque, speed regulation etc. figure into it. Maybe even a hydraulic motor would end up on top. \$\endgroup\$ – Spehro Pefhany Sep 1 '17 at 4:32
  • \$\begingroup\$ What will the motor used for? \$\endgroup\$ – Marko Buršič Sep 1 '17 at 6:39
  • \$\begingroup\$ No scheme for controlling a single-phase AC motor will be suitable for any load other than a fan or centrifugal pump. If it is a fan or pump, the performance will be strongly dependent on a close match between motor and load. If you value your time and need reliability, don't use anything used, improvised or sold without documentation. \$\endgroup\$ – Charles Cowie Sep 1 '17 at 10:37

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