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34573Re: [mill_drill] vfd speeds & power

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  • CS Mo
    Nov 7, 2013
      Unless you have an inverter-duty motor, I wouldn't run it below 30-45hz. If I want a really low speed, I typically set my variable speed head to 140 rpm (lowest it will go) and then set the VFD to 30hz, which comes out to 70rpm. I use that setup for manually running a rigid tap and I've used 12mm thread forming taps in aluminum and 1 1/2" NPT taps with that without bogging down the motor in any way.

      I couldn't tell you how much 'power' was actually available though. (I'd imagine, at 30hz that it'd be 1/2 the nameplate power).

      My understanding is that the main problem is the motor overheating at lower rpm. A VFD and a non-inverter-duty motor will NOT give you a full range of rpm from 0-to-xxxx. A VFD and a high quality inverter-duty motor, or brushed AC servo-class motor, might get you close to that though.

      --CS

      >on an 1800 rpm 1-1/2 hp motor, using a VFD, what is the lowest motor
      >speed that could be safely run ? I ended up selling my bridgeport with
      >a new vfd on it but never got to actually try it. .
      >
      >at, say 100 rpm, how much power would that 1-1/2 hp motor be
      >delivering ? 1/18th or very little ? or is there a multiplier somewhere ?
      >
      >what would the power requirement (amps running) be ?
      >
      >im sure this has been asked before but I have not see it.
      >
      >thanks
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