Re: [CAD_CAM_EDM_DRO] AC Speed Controller for Lathe: Meat or Accident?

Abby,
You might try doing a little R & D on a device called a VFD (variable
frequency drive). I'm driving my 1 1/2HP mill with it. My mill has a 2-speed
motor, and although the primary purpose for installing the VFD was, to
convert 3PH to 1PH, the bigger benefit is to be able to dial in speeds from
this little box. I don't know about the way it would function at very low
RPM, as you might like on a lathe, but I'm sure there are some other guys
out there, with that kind of experience.

Marv Frankel
Los Angeles

----- Original Message -----
From: "Abby Katt" <abbylynx@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, September 17, 2003 3:32 AM
Subject: [CAD_CAM_EDM_DRO] AC Speed Controller for Lathe: Meat or Accident?


> Swarfer-breatheren,
>
> I seemed to have (accidentally) bought myself a massive big old lathe
> at an auction. When I picked it up however, I found that the motor
> was some horrid 3-phase electical fire with a rats nest in it, so I
> dropped this and decided to just buy a new one of ebay. However: as
> I'm now missing the belt-drive and motor assembly I'll have to make
> this up.
>
> I thought this would be the best place to ask this: I'm thinking
> about building my own AC motor speed controller (with some
> thyristors) and just leaving the motor belted on one setting or the
> other. I was wondering what advice people would have on this? I'd
> have asked this on another forum, but as you all are so terribly
> nice, and experienced with this type of thing I thought I'd ask here
> (and hey! I'll probably convert the lathe to CNC in the future
> anyway. :) )
>
> So what's the deal? Is this good science, or bad science? Will the
> lower voltage mean the motor will turn really slow, but also have no
> torque what-so-ever? Should I use some other kind of circuit? Or is
> this is all just a terrible idea that's going to wreak havoc on the
> electrical grid for blocks around as I throw rude-pulses at a 2KW
> motor? Should I use a DC motor instead? (I want to do this on the
> cheap, really)
>
> BTW> This is a BIG old lathe! 5foot long and weighs.. well.. the
> tailstock weighs about a third of my weight. :P
>
> Thanks for your advice!
>
>
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