How about taking a Variac transformer, adding a full wave rectifier
bridge and connect that to the drill. Series connected motors work a
lot better on DC than AC. You can better torque that way. Just remember
that you can push more current through the motor with DC so you have to
watch out not to overheat the motor. At low RPM it is most resistive
losses that cause heat generation.
A variable frequency drive will work as it is also varying the output
voltage with the output frequency but that is kind of overkill driving
a drill motor or any other "universal" AC/DC motor.
73 de N2JFS - Hans
-----Original Message-----
From: Gary Schafer <garyschafer@comcast.net>
To: 'Dennis Vernacchia' <n6ki73@gmail.com>; 'Richard (Rick) Karlquist'
<richard@karlquist.com>
Cc: 'towertalk' <towertalk@contesting.com>
Sent: Thu, Oct 15, 2009 6:59 pm
Subject: Re: [TowerTalk] Reply - KW3000 with 1/2 inch Drill Motor
-Wrongassumption in responses
Maybe some confusion here? A typical AC/DC motor has the fields wired in
series with the armature. This allows the motor to run on either ac or
dc
voltage as it does not depend on the rotating fields that AC provides
in a
typical AC only motor.
With the series fields/armature a lower voltage will cause the motor to
draw
more current and increase the torque. A light dimmer should work to
control
speed.
A variable speed (variable frequency) drive will do nothing for the
series
wired motor to control speed. It will work the same if it is operated
on 60
Hz or 30 Hz or DC.
73
Gary K4FMX
> -----Original Message-----
> From: towertalk-bounces@contesting.com [mailto:towertalk-
> bounces@contesting.com] On Behalf Of Dennis Vernacchia
> Sent: Thursday, October 15, 2009 2:36 PM
> To: Richard (Rick) Karlquist
> Cc: towertalk; Chuck Frame; Dubovsky, George
> Subject: Re: [TowerTalk] Reply - KW3000 with 1/2 inch Drill Motor -
> Wrongassumption in responses
>
> Rick,
>
> I was told by a friend who is knowledgeable about the subject that
yes,
> the
> drill converts AC to DC so
> not a candidate for Pulse Width Motor Speed Controller
>
> I need something off the shelf as I don't have time to reinvent the
wheel
> right now.
>
> Will have to wait for a solution on reflector unless you come up with
> something in your quest
> for same thing I need.
>
> 73, Dennis N6KI
>
>
> On Thu, Oct 15, 2009 at 8:13 AM, Richard (Rick) Karlquist <
> richard@karlquist.com> wrote:
>
> >
> >
> > Dubovsky, George wrote:
> >
> >> You will still lose torque with a pwm light dimmer. You will need
> >> something like an variable speed drive, where you vary the drive
> frequency
> >> and voltage simultaneously, essentially synthesizing a complete
sine
> wave at
> >> an adjustable frequency. I use them on three-phase motors on my
lathe
> and
> >> mill, but they are also available for single-phase motors. Not
cheap,
> but
> >> less than the Hole Hawg ;-)
> >>
> >> 73,
> >>
> >> geo - n4ua
> >>
> >
> > The idea of the PWM method is that you have full torque when
> > on, but are not on all the time. You do lose horsepower, but
> > not torque, AFAIK. It's similar to pulsing the ON/OFF switch
> > on the drill. I am not sure if there is any difference between
> > a PWM motor speed controller and a light dimmer.
> >
> > A variable frequency drive sounds like something for an AC induction
> > motor. Most drills AFAIK are AC/DC motors, for which frequency is
> > obviously irrelevant.
> >
> > If the above is wrong, someone correct me. I want to get a
> > Hole Hawg too, as soon as I figure out how to slow it down.
> >
> > Rick N6RK
> >
> _______________________________________________
>
>
>
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