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Old Aug 20, 2004, 03:38 AM
The blade numbers go up to 11
stumax's Avatar
Sydney, Australia
Joined Aug 2002
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What's best for direct drive 1-1.5kW @15K rpm?

Hi guys, I have a project which requires a motor to draw about 1-1.5kW @15-16K rpm with max efficiency, and retain the efficiency throttled down to about 1/3-1/2 throttle. I'm looking at 20 and 30 cells for the 1-1.5kW. Physical size isn't important (up to 75mm dia, anyway), but weight is. No gears, as it has to be able to take that power for 15 minutes or so, with no maintenance or noise. I'm thinking outrunner (probably non LRK type winding) but the commercial ones don't seem to go fast enough, or high pole count inrunner. Preferrably something off the shelf (not as expensive as a Tango!), as I no longer have machine shop facilities to make it myself. Thanks!

Stu.
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Old Aug 20, 2004, 04:33 AM
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max.ferra's Avatar
Padova, Italy
Joined Oct 2002
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Quote:
Originally Posted by stumax
Hi guys, I have a project which requires a motor to draw about 1-1.5kW @15-16K rpm with max efficiency, and retain the efficiency throttled down to about 1/3-1/2 throttle. I'm looking at 20 and 30 cells for the 1-1.5kW. Physical size isn't important (up to 75mm dia, anyway), but weight is. No gears, as it has to be able to take that power for 15 minutes or so, with no maintenance or noise. I'm thinking outrunner (probably non LRK type winding) but the commercial ones don't seem to go fast enough, or high pole count inrunner. Preferrably something off the shelf (not as expensive as a Tango!), as I no longer have machine shop facilities to make it myself. Thanks!

Stu.

Could be the MEGA RCn 41/30/10 a good choice?

http://www.megamotorsusa.com/Brushle...-10.htm?id=103

It should be good up to 30 cells (so RPM isn't a problem), althoug it's reccomended only up to 16 direct drive. Keep the prop well balanced :-)

Max
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Old Aug 20, 2004, 05:15 AM
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henke's Avatar
Sverige, Kronobergs Län, Ljungby
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I was not impressed with the big Mega outrunner, rather go for the AXI then.

but are´t those outrunners made for 5-7krpm?! Thinking a larger inrunner might do the job better at those higher rpms. A larger lehner or maybe the Mega 22/45/3 can do 1Kw or so.
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Old Aug 20, 2004, 05:34 AM
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max.ferra's Avatar
Padova, Italy
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Quote:
Originally Posted by henke
I was not impressed with the big Mega outrunner, rather go for the AXI then.

but are´t those outrunners made for 5-7krpm?! Thinking a larger inrunner might do the job better at those higher rpms. A larger lehner or maybe the Mega 22/45/3 can do 1Kw or so.
The Mega 22/45/3 has a too high RPM/V.
On the homepage they're saying that the Mega Outrunner (Kv=570) is good up to 32 cells, so max RPM should be up to 18KRPM

BTW I pulled my Flyware TRex 40 up to 11 KRPM easily :-)
May be the Flyware TRex 20/700 could be a higher efficiency option.
http://www.flyware.de/pd-763346213.htm?categoryId=7
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Old Aug 20, 2004, 05:48 AM
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The Aveox 46/43/2 would do it, on 25-30 cells, depending on the load, rated for 50A continuous, 120A peak.
..a
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Old Aug 20, 2004, 10:10 AM
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Chicagoland
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Aveox 46/43 costs twice as much as a Tango!

Stu, If part throttle efficiency is an issue, I think Tango will be the best way to go. You are looking at a 500USD system. If there was one cheaper that worked everyone would be using it. Nobody here is hiding that kind of secret.

Greg
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Old Aug 20, 2004, 10:25 AM
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Padova, Italy
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Tango is a "slotless" motor, with a low inductance, hence I think part throttle efficiency could be difficult to be reached, expecially without a high-end (and expensive), high frequency PWM ESC.

Max

Quote:
Originally Posted by gkamysz
Aveox 46/43 costs twice as much as a Tango!

Stu, If part throttle efficiency is an issue, I think Tango will be the best way to go. You are looking at a 500USD system. If there was one cheaper that worked everyone would be using it. Nobody here is hiding that kind of secret.

Greg
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Old Aug 20, 2004, 10:59 AM
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Kontronic makes a controller specifically for this motor.

Greg
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Old Aug 20, 2004, 12:19 PM
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henke's Avatar
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are you sure that Tango is slotless?

anyhow, the outrunner it self might work, but does the ESCs take a 14pole motor to 20krpm? (unloading in flight)

if so it might do the work as well as any other motor.
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Old Aug 20, 2004, 12:22 PM
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I have an Aveox's 36/38/3 has a kv=700, which is said to be capable of 1Kw output, and is able to have rpm of 40,000 with its carbon (?) wrapped rotor,though I have not put in actual use, I ran some no. in dd, hope may be useful to you:

+14x9,5 graupner cam+8 GP3300 AT 10,6V=32,1a, 278w
+" "" +10GP at 13,4V= 42,1 436
+16X10 graupner cam+ 8GP AT10,5v= 39,0 319

I believe 1Kw is surely reachable if right combo is used, I will run some more combo if time is allowed.

David
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Old Aug 20, 2004, 12:38 PM
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Tango is a slotless and coreless design.

Greg
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Old Aug 20, 2004, 02:36 PM
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CharlieS's Avatar
Ithaca, New York, USA
Joined Jun 2001
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Here are the results from the Aveox virtual test stand for the 36/38/3 motor.

Seems close to what you want, but probably would require excellent cooling to take the 50 A for 15 minutes. Its rated for 28 A continuous and 65 A max.

I use the 36/38/2 DD on 10 GP 3300 at 600 W. The test stand gives excellent agreement with my measured data, so I think you can trust it.

Charlie

Open Circuit Voltage 1.25 Volts X 25 Cells = 31.25 Volts
Battery Resistance 0.0045 Ohms X 25 Cells = 0.1125 Ohms
Speed Controller Resistance = 0.010 Ohms

--------------------------------------------------------------------------------
Motor Type 36/38/3
Motor, Unloaded 700 RPM/Volt
Motor Resistance 0.050 Ohms
Motor no-load current 1.00 Amps
--------------------------------------------------------------------------------
Prop Type APC Prop
Propeller Constant 1.11
Diameter 10.0 Inches
Pitch 6.0 Inches
Gearbox Direct Drive
Gear Box Ratio 1.00 :1

--------------------------------------------------------------------------------

Outputs
Prop RPM: 15978 RPM
Current: 48.8 Amps
Voltage into Motor: 25.3 Volts
Power Input: 1234 Watts
Power Output: 1092 Watts
Efficiency of Motor Only: 88.5%
Current at Max Motor Efficiency: 22.5 Amps
Pitch Speed: 91 mph
Thrust at Pitch Speed: 97 oz
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Old Aug 20, 2004, 05:59 PM
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East Anglia, UK
Joined Sep 2002
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Big Hacker - B50-XL?
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Old Aug 20, 2004, 07:56 PM
The blade numbers go up to 11
stumax's Avatar
Sydney, Australia
Joined Aug 2002
4,385 Posts
Thanks for the input guys! Max, I think the Mega outrunners aren't that efficient, and it's efficiency that I want most of all. The Mega 22-45-3 low KV would work but it's kv is a little high (I reckon I need about 680, it's 800). The Aveox look promising, and I also checked out their virtual test stand with the 36-38-3. Expensive, but efficient. Tango is too expensive. Actro 24-3 looks promising, again, rather expensive. A 2 pole motor like a Hacker or Lehner would most likely be less efficient than a Mega at these rpm. I have a B5012XL which I might just gear down 2:1 or thereabouts just to test out my concept, then look further. BTW, it's for an EDF concept I'm working on, with a larger than normal hub and rotor dia (but same swept area as a Schubeller) with a large blade count to see if I can get it sounding more like a turbine. I'm interested in part throttle efficiency as these days I reckon full throttle is more like afterburner - only used for a short while when necessary - and if you spend most of your time at part throttle that's the area you should be looking for efficiency.

Thanks guys!

Stu.
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