Re: rod-mill project - "mains" electric motor advice

"Jim Wilkins" <muratlanne@gmail.com> writes:

"Richard Smith"  wrote in message news:m1v7pjhzvs.fsf@void.com...
>
Update these many weeks later...
>
...
>
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Congratulations. Did you learn anything worth sharing about designing
and building low budget powered machinery?

Yes

* blag anything and everything you can - gifted or "on unspecified loan"

* have a lot of mates

* volunteer at societies so you meet people and are not floundering alone

* help others, so help comes back to you

* do go out and do other things - take time out - it's amazing how you
  can bump into people who know about what it is you are doing

* as ever, there's the balance between:
  think it through, often doing calculations
   ^
   v
  get tools in your hands, get started, and try what seems possible

* if you face a significant capital cost, think what it's worth to you
  in a lifetime.  Whatever it is is likely to have some use, and "going
  for it" "opens doors".

Technically:

Speed control is now in power-electronics.

Expanding that:
speed control of electric motor powered machines is now using
power-electronics using the "inverter" principle.  They've "hit the
mainstream".

It goes:

"mains" 1ph
 v
VFD (Variable Frequency Drive) - "inverter" VFD
 v
3ph electric motor
 v
{mechanical drive to application}

I find that in places like the Philippines (what "the West" would call
"third world") they have been improvising specialised machines for
several years - approaching 10 years now - certainly 7 years judging by
YouTube videos.
The VFD's (Variable Frequency Drives) all look about the same.
Probably one source - or a city where all the makers are concentrated
using overwhelmingly the same components.

The cost of the VFD's is some fraction of the cost of the motor - less
than 1/3rd - typically more like 1/4.
Begs the question - why bother with a single-phase motor any more?!?
3-phase motors are self-starting, robust, smooth torque - and no
"wearable" components like capacitors.
Have as many VFD's as you have motors.  The VFD's are interchangeable.
So what if you have one or two spare if you have many applications
in-use...
???

The ability to "chop" at higher than the input frequency - empirically I
found that that implementation of the rod-mill was optimal at 55Hz to
the motor.
Our mains here is 50Hz...
That bit of "headroom" "saved the day".
(the device, the VFD, refuses to go above 60Hz output - likely don't
want "the heat" from people turning up at hospital with bits of motor
embedded in them?)

That's about it.
Glad I went for it.
On the "in a lifetime" principle.  Work came to a stop while
international trade re-aligns and I went for this.
Other story here for me is that we have got a diamond core drill working
at our hobby mine nearby - and there is some chance of that leading to
gainful employment.  The thing would need a 300HP compressor "at grass",
but we can run it in bursts on the air in the air-main acting as a
receiver.  Has a 20HP (?) air-motor.  Enough while we go through the
learning curve.
So I have had two big themes in this time.

And ... I have taken the time writing to you all, as a thank-you for
timely advice and suggestions.  I've had a coffee while doing it.  I
have quite a list of to-do's and missions today.

Best wishes from here in Cornwall, England.