Re: [CAD_CAM_EDM_DRO] UPS to VFD hardware hack

Hello Doug,
Sounds like a very usefull proposal. If it work out I will be one of the
first ones to play with it. Sad that I am not an electronics but I will
ask a neigbour who is development engineer at Numatics.
It may take a few days to get an aswer.
Sven Peter

Doug Fortune wrote:

>
> A UPS (uninterruptable power supply) works by:
> - taking input of 60 HZ AC
> - converting to DC, possibly storing in battery
> - converting DC back to 60 HZ AC (called inverting or inversion)
>
> Somewhere in the inverter circuitry, there must be a
> 60 Hz reference oscillator (and of course, a 50 Hz
> reference oscillator would be installed in England),
> required in order to synthesize the output waveform.
>
> As it happens, the output rpm of AC motors are locked to this
> frequency, but if the frequency changes (say 15 Hz to 120 Hz)
> then the basic speed of the AC motor can go from 25% to 200%
> of its normal rpm.
>
> I had the idea that this fixed oscillator be hacked out,
> and a variable frequency source be installed in its place,
> thereby possibly achieving an inexpensive AC VFD
> (variable output frequency motor driver).
>
> This pertains to CCED in that this variable frequency
> is controlled somehow by the computer, leading to
> variable speed spindle control (of your lathe or mill).
>
> Has anyone got any intuition as to whether this might
> be possible? Inexpensive UPS's are available up to
> 1500 VA (approx 2 HP).
>
> Doug Fortune
> http://www.cncKITS.com
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