Gary Schafer wrote:
> Maybe some confusion here? A typical AC/DC motor has the fields wired in
> series with the armature.
If my poor memory serves me correctly from a class in motors some 40 odd
years back, series motors are poor for generating torque compared to
parallel. That's probably why the *old* Craftsman was big, heavy, and
would twist your arm off while todays high powered drill motors are much
smaller, lighter, and overheat easily.
73
Roger (K8RI)
> 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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>
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