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Wide Speed Range

Wide Speed Range

Wide Speed Range

(OP)
What's the best choice for a motor with a wide speed range requirement?  This application will spend 99% of it's operating life at low speed and 1% at 130x.  Other desired features are feedback, high reliability, long life, and low cost in high volumes (> 10k/yr).
Thanks!

RE: Wide Speed Range

10,000HP? 10kW? 100W? What kind of speeds, 1RPM to 130RPM? 100RPM to 13,000RPM? What kind of feedback? Encoder? Tachometer? Torque? Temperature?  Long life as compared to a residential kitchen appliance or a piece of Mill Duty machinery? Low cost relative to components in toy planes or military aircraft?

RE: Wide Speed Range

(OP)
Output operating speed is 15°/hr, so I think I'm looking at lots of gear reduction anyway, so input speed best chosen by motor/controller type?. Output load is 200 to 1750 Nm, so less than 200W. Positional feedback or encoder. Life 20 years or 70,000 operating hours. Low cost relative to the alternative choices that will do this kind of job.

RE: Wide Speed Range

I would say stepper motor with reducing gear. Careful gear design with a redundant electronics should do it.


----------------------------
Please read FAQ240-1032
My WEB: <http://geocities.com/nbucska/>

RE: Wide Speed Range

Do you haven't any requirements to speed smoothness?

RE: Wide Speed Range

blacksea...  His application requires the speed of an hour hand on a clock!  How much smooth do you want? lol Unless we're talking a telescope..reading

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Wide Speed Range

(OP)
Thank you, nbucska.  You expect that stepper motors and controllers will beat 3 phase ac motors controlled in "bang-bang" fashion on cost?  I sure have reliability concerns about the bang-bang approach!

blaksea, itsmoked:
I'm not familiar with how to specify a smoothness parameter - but you're right, itsmoked - it is exactly the speed of a clock - it is a solar tracking application.

Thanks all, for your comments!

RE: Wide Speed Range

If it's not for photography then I would suggest no 'smoothness' is required.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Wide Speed Range

How many of these units do you plan to use per installation?

To all:
What is the best way to protect the stepper motor/gear from
the environmental effects?

What about immersing the whole thing in oil?


----------------------------
Please read FAQ240-1032
My WEB: <http://geocities.com/nbucska/>

RE: Wide Speed Range

Consider a switched reluctance motor.  Essentially a large angle VR step motor.  Very robust....sunshine



RE: Wide Speed Range

Consider two motors and a set of magnetic clutches.
I suggest the slow motor driving a high ratio gear reducer. The high speed motor or the output of the gear reducer to drive the final reduction gearbox depending on which clutch is energised.
If this is a high torque application, consider air operated clutches.
respectfully

RE: Wide Speed Range

waross has a good point.  

You need to be able to move this whole thing a 100 times faster for installation, setup, and repairs.  If you are stuck at sidereal rates you will be... um in a hard spot. That is the whole hassle of designing telescope drives.  How to get it to slew at a reasonable rate while tracking at a slow enough rate to allow solid photography.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: Wide Speed Range

Are you just tracking the sun for a photoelectric or thermal mirror application?  If so, intermittant motion is OK.

RE: Wide Speed Range

(OP)
Gang, I appreciate all the attention!  Interesting comments.  
nbucska - one per installation if a polar drive (the seasonal drive only moves 1/8 degree per day, possibly with a linear actuator - or two for an az-el drive.  But the az-el drives have an even wider speed range requirement, going to theoretical infinite at azimuth.  I like immersion, but probably need to find it off the shelf...

sreid - yes, it's a thermal application, so slewing too slow, as Keith points out, is fatal.

waross - hard to imagine clutches achieving reliability or cost targets?

Clyde38 - (nice handle!) - looking into switched reluctance - thanks.

RE: Wide Speed Range

Honeywell had  a solar system with many large flat
mirrors individually servoed but they abandonned it --
I don't know why.

I wonder if it wouldn't be cheaper to use one -- or a few -- mobile "tuning" unit which on a rail could go from
mirror to mirror and re-adjust them one at a time ?

This would reduce the part-count and maintenance.



  


----------------------------
Please read FAQ240-1032
My WEB: <http://geocities.com/nbucska/>

RE: Wide Speed Range

I would use a system that can move 3 degrees a second and just ON and OFF it regularly.  That way you could slew it 180 degrees in a minute.  But still track better than probably needed.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

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