RE: [CAD_CAM_EDM_DRO] Re: VFD Selection

A small VFD as I am typically familiar with runs from single phase or 3
phase
(usually 240v) and puts out a 3 phase 240v suitable for driving an induction
motor. The frequency is variable over a wide range to control the rpm
of the motor. They could be designed to work with lower voltages, but 120vac
is not used much due to limited power and increased i^2r heating.

I guess the keywords here are CUT STEEL. You sure don't want to try that
with
the router...it's not built for it.

Using the shaft of a typical motor as a spindle likewise is not designed
for those forces.

I do think I have a design for a belt driven angular contact or tapered
roller bearing spindle that could be run from a single phase 120vac motor
at fixed speed (least costly), a dc motor/servo amp, or a phase control
(voltage)
dc motor over a limited rpm. It would have torque due to the gearing down.
I could try and find it for you if you have the capability to do precision
(+/-0.0002") machining with your tools.

Could you tell me more about what you want to cut and how fast? Sounds
like we are getting more into Milling machine territory. A steel cutting
gantry type machine is usually not in the hobby relm.

Les



Leslie M.Watts
L M Watts Furniture
Tiger Georgia USA
(706) 212-0242
http://www.lmwatts.com
Engineering page:
http://www.lmwatts.com/shop.html
CNC surplus for sale:
http://www.lmwatts.com/forsale.html
CNC carved signs:
http://www.lmwatts.com/signwp.html




-----Original Message-----
From: george_barr [mailto:george_barr@...]
Sent: Tuesday, April 13, 2004 4:28 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: VFD Selection


Leslie,
It appears that I cannot use a VFD or Variac to reduce my router to
1k rpm. What type of motor can I use with a VFD (input: 120VAC,
output: 120VAC or DC) without getting too expensive or without using
servo drives? Is there a specific phase specification. Does the
motor have to be AC or can it be DC? What I am planning to do is cut
mild steel (which requires low rpm speed)?

Thanks,