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,

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Leslie M. Watts"
<leswatts@a...> wrote:

> Your Bosch apparently has a phase control already built in
> as do my Porter Cables. So you don't need another.
>
> These speed controllers don't do too well at low RPM due
> to the lack of a tach or encoder rpm feedback. In any case
> 1000 rpm would be rough running. Series and compound wound
> motors just don't have low end torque. That is why the low
> end is designed to be 8k.There is just not much left below that.
>
> A VFD will not work with a universal wound brushed motor.
> Speed is voltage related in these, which is why Variacs
> were often used before phase control was cheap.
>
> Sounds like you need to drill holes in plastic, etc.
>
> I use a modular head where I can quickly bolt on another motor.
> A PM dc motor makes a pretty good light duty low speed spindle
> when driven by a dc servo amp, and doesn't cost so much if
> purchased surplus.
>
> A dc servo amp MIGHT work with a router
> if a tach was added and the phase control bypassed, but it
> would be a hassle-and although most router motors would work
> on dc they might not be rated for it. They are definitely
> not designed for heavy spindle loads either.
>
> I work a bit with portable power tool engineering, and we are
> all looking forward to the day when all of them use brushless

polyphase

> induction motors with frequency control. It will happen- but right

now

> commutators are still used due to the cost of brushless drive power
> electronics.
>
> 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
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> http://www.lmwatts.com/signwp.html
>
>
>
>
> -----Original Message-----
> From: george_barr [mailto:george_barr@y...]
> Sent: Tuesday, April 13, 2004 3:17 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: [CAD_CAM_EDM_DRO] Re: VFD Selection
>
>
> Leslie,
> It seems to me a Variac only limits the voltage going out. I
> already tried a variable router speed controller found at:
> http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?

itemnumber=43584

>
> This router speed controller does not work since my rouers normal
> speed range is 8k - 20k rpm and I need to have a speed of about 1k
> rpm. The speed controller cannot slow this router below 8k it
> seems.
>
> Are you saying that a VFD cannot work with my router?
>
> Thanks,
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Leslie M. Watts"
> <leswatts@a...> wrote:
> > George,
> >
> > You don't need a VFD for a unversal wound router motor.
> > It's speed is not dependent on line frequency.
> > Typically a phase control triac system is used. It is similar
> > to a light dimmer but has IR comped backemf or tach feedback
> > to contol the speed.
> >
> > Granger, MSC, etc have many of these, and some are well under
> > $100.
> >
> > A variac works as well, but with poorer speed control.
> >
> >
> > 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@y...]
> > Sent: Tuesday, April 13, 2004 2:34 PM
> > To: CAD_CAM_EDM_DRO@yahoogroups.com
> > Subject: [CAD_CAM_EDM_DRO] VFD Selection
> >
> >
> > I want to get a VFD for my Hitachi M12V router so I can vary the
> > speed for metal, aluminum, and wood milling. The M12V is a

single-

> > phase series commutator motor, 115VAC, 60HZ, 15 Amps router. I
> would
> > like to use my 120VAC outlet for the VFD. Can someone tell me

what

> > kind of VFD I should get? I have noticed some VFD have 3 to 1

phase

> > conversion and all sort of specifications. I certainly do not

want

> > to buy the wrong one. Also, it should interface to my pmdx.com
> break
> > out board.
> >
> > Thanks,
> >
> >
> >
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> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
> aol://5863:126/rec.crafts.metalworking or go thru Google.com to

reach it if

> you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to

be a

> sister site to the CCED group, as many of the same members are

there, for OT

> subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING

THEM.

> DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> bill
> List Mom
> List Owner
>
>
> Yahoo! Groups Links