RE: [CAD_CAM_EDM_DRO] Re: VFD Selection

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
CNC carved signs:
http://www.lmwatts.com/signwp.html




-----Original Message-----
From: george_barr [mailto:george_barr@...]
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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