Wide Speed Range

[SilverGlyde]

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!

 

[jraef]

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?

 

[SilverGlyde]

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.

 

[nbucska]

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




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[blacksea]

Do you haven't any requirements to speed smoothness?

 

[itsmoked]

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

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[SilverGlyde]

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!

 

[itsmoked]

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

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[nbucska]

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?



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[Clyde38]

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

 

[waross]

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

 

[itsmoked]

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

 

[sreid]

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

 

[SilverGlyde]

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.

 

[nbucska]

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
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[itsmoked]

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