[Stoves] Question regarding motors

[joe breskin]

On Tue, May 29, 2012 at 11:35 AM, Steve Taylor
<steve at thetaylorfamily.org.uk> wrote:
>
>
> On 29 May 2012 20:27, Frank Shields <frank at compostlab.com> wrote:
>>
>> Stovers,
>>
>>
>>
>>
>>
>> I want to turn a frame holding solution of biochar along with toxicants to
>> determine up-take potential. Also to turn wood and biochar  pellets to
>> determine hardness. It needs to turn at 30 and 50 RPM.
>>
>> Can I use a ¼ HP motor with a Variac ? I have a motor ordered that turns
>> at 52 RPM (gearing included) and would like to fine turn it to 50 rpm then,
>> if it will not destroy the motor, adjust it down to 30 rpm with the same
>> variac.
>>
>>
>>
>>
> No, sorry, to assuming its an AC motor, you'll burn it out in short order.
> AC motors tend to run at a multiple of mains frequency, or a shade off. When
> they are run under-voltage, then there isn't sufficient current to convert
> into torque, but enough current to convert into heat, and they'll burn up.
>
> For proper speed control, I recommend an AC inverter drive like this one
> from Ebay.
> http://www.ebay.com/itm/Allen-Bradley-PowerFlex4-0-25HP-0-230VAC-Drive-22A-V1P5N104-/270941251762?pt=LH_DefaultDomain_0&hash=يتيمعف١خخبطضبء
>
> Steve
>
>
> _______________________________________________
> Stoves mailing list
>
> to Send a Message to the list, use the email address
> stoves at lists.bioenergylists.org
>
> to UNSUBSCRIBE or Change your List Settings use the web page
> http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
>
> for more Biomass Cooking Stoves,  News and Information see our web site:
> http://www.bioenergylists.org/
>
>

my sense is that it will be cheaper and easier to
1. design around the motor you've got
2. buy a gearmotor made to operate at the speed you want,
3. add a secondary geartrain made with off-the-shelf part - either
gears, belts and pulleys, or chain and sprockets