motor speed control 2

[charland]

Hi guys,
My apologies if this is a simple question that has already been answered but I wasn't able to find anything helpful in the archives.

I'm designing a glorified dryer. The point of this machine is to tumble clothes at a specific speed over a specific time to condition them for other tests. The trick is that the spec requires a tumble speed of 5 rpm +/- 2%.

Ideally I would like to use an AC motor and hope that it stays within the right speed range and then just use belts and pulleys to ramp down to the correct speed. The torque load should be fairly consistant (my guess is ~0.2 hp +/- 5%). If I have to, I could use a DC motor, with some kind of feed back.

So my questions are:

Would an AC motor deliver a consistent enough speed over my torque range?

If not, are there any simple/good DC motor and controller packages that would work? I would like to avoid the purchase of a PLC if I can. (I found this option, which seems both appealing and confusing to me

http://focus.ti.com/lit/an/sboa043/sboa043.pdf

)

Thanks in advance

Charlie

 

[itsmoked]

Here's an example. (Sure to make Jeff shudder)

Scroll to the second page - top three VFDs.

http://factorymation.info/acdrives/fm50brochure.pdf

Almost obsoletes single phase motors all together.

Is a 3/4HP three phase motor $99 less than a 3/4HP single phase?


Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

In 1/4 hp and 3/4 hp sizes there is not that much difference between 1 ph and 3 ph.
At 1/4 HP grainger has about 25 single phase motors under $100.
Ignoring multi speed motors, wash down motors, brake motors and other special motors, there are are about 80 in the $100 to $200 bracket.
Most 3 ph, 1/4 HP motors are in the $100 to $200 bracket.
The prices for 3/4 hp ratchets up about $100 but there is still not that much difference between 1 ph and 3 ph.
BUT, I like the price on those drives. It won't take much of an excuse to add a VFD drive to a project at those prices.
Thanks for the info, Keith.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[roydm]

Skogsgurra,
"115 V in 230 V out", I think these have a voltage doubler on the input (2 diodes and a capacitor) to give 230 VDC at the bus. I used one recently to give me 3ph 400Hz for a tiny submersable well pump.
Regards
Roy

 

[itsmoked]

Where did you find a 400Hz motor as a well pump?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[roydm]

Keith,
It was a Grundfos Redi-Flo2 pumping 7gpm @ 100ft head
2 HP @ 23,000 rpm (yes 23 thousand) The website is

http://www.grundfoss.com

I have seen 400Hz power tools also, but not recently
Roy

 

[roydm]

Keith,

http://www.grundfos.com

In the environmetal section. I used a Mitsubishi drive, not the Grundfos.
Roy

 

[itsmoked]

Cool! Thanks Roy.

Keith Cress
kcress -

http://www.flaminsystems.com