Could you suggest a rotary electric motor, rated at 5...10kW, with smaller cross section area, say, 5-6 square inches or possibly less? Length is not critical. Could be of any type (brush, BLDC, reluctance, AC...), with windings rated at few hundred volts. Precise controllability is not required; price is not very critical. I am having difficulty in finding any motor in kW power range that would fit small cross section requirement.
Vladimir Vassilevsky DSP and Mixed Signal Consultant
I'm not an expert on motors but I think I see a problem.
Large motors are rated in horsepower, not watts. 5 to 10kW would be
6.7 to 13.4 Hp. I'll round off to 5 to 10 Hp. Motors are also sized by diameter, not area. 5 - 6 sq in would be about 2.5 to 2.8 inches diameter. That's a mighty powerful motor, in a very small package.
Looking at commodity motors in the 5-10 Hp range on eBay, there's nothing even close to that small:
There's another problem. In order to deliver 5 - 10 Hp, the output shaft will need to be a fairly large percentage of your proposed diameter. For example, a typical 5 - 10 Hp motor, in a NEMA 184T or
215T frame, the shaft will be 1 1/8" or 1 3/8" in diameter. That doesn't leave much room for the rotor windings, stator, air gap in a 2
3/4" diameter.
Motor formulas:
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Jeff Liebermann jeffl@cruzio.com
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That's about ten horsepower? Five square inches is a diameter of 2.2 inches, and one would expect a 0.75 inch shaft. Well, it's POSSIBLE, of course (superconducting motors are just a little wider than their shaft). The only off-the-shelf idea I come up with, is to put lots of small motors behind impellers, and drive the output shaft with a hydraulic motor (i.e. no gears, just turbines).
Motors tend to have torque proportional to their volume, so that motor would have to be spinning *fast* to make that much power.
Cheers
Phil Hobbs
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Dr Philip C D Hobbs
Principal Consultant
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You might need some pretty serious bearings to prevent shaft whirl, and of course the slip rings for motors 2...N would have to run pretty fast as well.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
If you really need to fit a motor that powerful into a small space you might look at running a hydraulic motor from an electric power pack.
I think it will be more like 4" diameter even so.
Best regards, Spehro Pefhany
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I once found myself surrounded by MEs who were stumped by the problem of using a mechanical indicator (odometer mechanism) to count steamship shaft rotations in both directions. I had to invent the mechanical full-wave bridge rectifier for them. It's surprising how many concepts are obvious to circuit designers but not to others.
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That's essentially what submersible motors intended for borehole use do - t= hey have multiple rotors on the same shaft within a common stator. The one= s used for artificial lift in oil wells would typically have a 5.5" OD and =
That's partly because we can get magic beans from Digikey for $0.05 in single quantity. Imagine trying to make the mechanical equivalent of a triac.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
... and stand back while the second or third motor from the open end breaks its shaft, or the shaft as a whole succumbs to torsional vibration and snaps.
... and stand back while the second or third motor from the fixed end flies apart from centripetal acceleration, or the whole assembly succumbs to torsional vibration.
Not to rain on your parade too much...
--
My liberal friends think I'm a conservative kook.
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Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
As mentioned -- that's way too small for a number of reasons. If the torque requirements of a low-speed motor don't get you, the dynamic issues of a high-speed motor (shaft resonance and centripetal acceleration) will.
I used to work with a guy whose previous job was at a purveyor of aerospace brushless motors. For several months at one stretch, his job was to spin motors so fast they disintegrated from centripetal acceleration or other effects, in a search for a really small, really powerful motor.
You didn't say anything about speed or efficiency. Maybe a bunch of smaller motors that are geared, belted or chained to a common shaft? It'd be way expensive, and a bitch to assemble, but maybe doable. All my replies to Mr. Larkin's post still apply, although if you make a beefy, hollow shaft you may be able to dodge some of them.
Can you get by with a motor (and perhaps gearhead) that has a really long snout, that can live outside of whatever long, narrow hole you're contemplating to use, and just pokes the output shaft in for power?
If not, then maybe a custom hydraulic motor is in your future.
--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?
Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
That's a really extreme requirement. The closest that I'm aware of is a treadmill motor: about 3" diameter (7 sq in) & 2 hp. Small shaft, but high rpm (6000 - 7000). You're definitely going to have to deal with high rpm - it's unlikely that a very small diameter motor will have much torque. Oh, I suppose it could with really humongous current.
Please let us know if you do find one - it would be very interesting.
--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?
Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
After being so discouraging in previous posts, I just realized that immersible well pumps are muy powerful and not much bigger around than what you want.
Of course, they're designed with the expectation that there's going to be water flowing around them like mad, so to use one in your environment may require some (heh heh) attention to cooling. At a guess, given that they're plain ol' induction machines, at least two or three kW for your
10kW output case (and you'd need to check efficiencies to be sure).
The one that came out of my well a couple of years ago is 3.75" x 12". The starter is for a 10HP motor, so I _assume_ that's what the motor is.
But do some internet shopping and see what you come up with.
--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?
Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
Here's one (OMM50) with the hoses coming out the back (not that common!) that can produce >3 kW (> 4HP) and is only 60mm (2.36") in diameter (4.4 in^2).
formatting link
Best regards, Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Parents were from Poland. I was born in Germany and came to the USA in 1953. I do not own a horse or know how to operate one.
For your amusement, please note that bicycling uses horsepower:
I've also noticed that exercise treadmills display output in horsepower.
Please let me know when the industry replaces the term "fractional horsepower" motors with "fractional kilowattage" motors.
I call to your attention the eBay listing for electric motors:
Note that the selection criteria on the left is by horsepower, not kilowatts.
Prior to the popularity of hybrid automobiles, just about everything was in horsepower. The problem was that hybrids would have a rather low rating if specified in hp. Since the motor burned electricity, it would also make sense to specify the motor in kW. Customers should not be allowed to compare a 44 hp Prius with a 300 Hp Detroit gasoline burner. Much easier to just change the units of measure.
Then, there are variable speed motors: "The problems of Horsepower Ratings"
and creative specifications:
Sigh...
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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