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The kind of solder joints I'm looking for.
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η = Power output/(Power output + power losses)
The Power losses are stator core losses, rotor eddy losses, and the stator winding losses
Power = (T)(ω)
T= Torque
ω= rotational speed (rad/sec)
Therefore...
η = (T)(ω)/((T)(ω) + stator core losses + rotor eddy losses + stator winding losses)
When you look at this mathematically why does the ONE in Germany think that the winding losses are greater than the other 2 sources of loss so they become insignificant to having an effect on improvement of eta? How could a hybrid wind be a gimmick if they can reduce those other losses as much as 60%. The other thing to you should consider from Dr Dorell's work is if the AC winding losses are 10 times that of the DC they actually have a more profound effect on winding losses thus the ETA than the measured dc resistance at any give frequency. DC is stall .... no frequency. As theory has it the stranded wire also actually has more surface area so it will run cooler and in effect not gain as much resistance as the solid wire from heating effect.
Hope this helps.
HubertComment
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Mechanical power output In Imperial units
hp = (T)(nrpm)/5252
T = torque (ft-pounds)
1 ft/lbs = 1.3558179483 Nm
1 imperial hp = 745.7 wattsComment
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Powercroco wrote:
"And I'd rather spare you my comment about when engine efficiency is evaluated on the basis of propeller thrust."
'Thrust has the unit [N] with the unit name Newton, it is neither a form of energy nor a power. How to get from the stationary thrust of a propeller to an efficiency of one BLDC is a matter of questioning.
'
Greetings
Micha
Itz easy Ralph. You don't convert that. You measure how much torque and rpm you have there at the prop and use the formulas I just showed you to determine η .
Audiosmith should check his Tmotor efficiency this way because based on a propellor performance chart which gives the torque and RPM at 100 percent throttle the AM600 T motor with a T16x8 only gave back η=.74 with a prop efficiency of 3.86 grams per watt. Just convert the torque values from newton meters to foot pounds. You see the Torque value, and RPM at the prop, and input power consumption so this is easy to do. I calculated approximately 1,456.32 watts mechanical at the prop. If my calculations are off anyone may correct me.
Audiosmith wrote:
"With this winding, it can still be operated sensibly with 68A, the syncloss current is 70A, which is 1.5kW with only 35g, so crazy 43W/g.
At this speed, you can still use a YGE 35 LVT with max. 243000 field revolutions and if you cool it well, you can load it up to 60A.
For stand measurements, I shortened an APC 5.5 x6.5 and an APC 5.25 x8 accordingly, so that at 22.2V 59A at 33500U were set.
The 4.5 x6.5 is therefore suitable for flying in at a good 300kmh, while with the 4.1 x8 you could already scratch the 400kmh mark.
It was fun to improve an extremely good engine, let's see what else comes along...
VG Thomas Schmidt Appendixes"
So the discussion from you and Micha is a bit off Ralph, because he is not giving thrust grams per watt he is giving wattage draw versus the weight of the motor. To me that's a comparative metric that doesn't mean a lot because I can make any motor pull more amps to increase that value but that doesn't make it more efficient. The motor has no mass and a high Kv so it has a low torque constant. You need reactionary torque measure on the motor and the prop with rpm to determine the motors real Eta
And as I suspected the little thing makes average thrust for the power consumption. It never goes beyond 3.8 watts a gram on the 3 props tested. This is average prop efficiency so the motor is probably still right around the 74% mark in eta. I doubt very seriously if it is the outlier.
T-MOTOR F40 PRO V 1950KV 2150KV FPV BRUSHLESS DRONE MOTOR (tmotor.com)
We have cots motors doing over 6 grams/watt
Thanks
Hubert
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If you want a formula of systematic improvement of a motor then why not look at PSO or particle swarm optimization?
TTYL
HubertComment
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Hi Ralph 😀
I see you pulled up at 7:23 EST
Tell Audiosmith his power to weight estimates are also inflated because he is going off the electrical wattage not the actual mechanical output . 🙈🙉🙊
A reactionary torque measure versus inline is only speed limited to the DUT and the prop.
Thanks
HubertComment
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Hi Dr Okon,
You'll be here so so Let me help you, Audiosmith, and Gerd's social media, learn how to quantify and measure things to evaluate performance of a propeller contra drive system and the motor. 😂 To build off the Formulas I've already provided you from the field let me turn your attention to the Sage International Journal of Micro Air Vehicles and in particular an article published in volume 11 pages 1-12 in 2019. Characterization of ducted contra-rotating propeller propulsions by Longfei Zhao and Sergey Shkarayev.
First, this is the motor efficiency formula they use....
Maybe you can accept this one. 🙄
ηm=( 1 - io/i )( 1 - iR/v)
i=current and v=voltage taken at the input of the ESC . io and iR are given in a motors measured parameters . They are usually provide by the manufactures except MHZ and your 7455..
Taken from Drela M's First order dc motor model. Technical report, MIT Aero and Astro, Feb. 2007. It is the same efficiency formula as maxon 1.92 Ralph just expressed differently. Can you see? Idle current, stall current, and resistance 🤓
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Hi Ralph I saw bingo was at 1:06 am EST but there's more I know you'll be here now...🤣 You want to record your input power, thrust force, and revolutions per minute . For analysis of the ducted fans and open contra system you can employ a non dimensional thrust coefficient
CT= T/pn2D4
D= propeller diameter
n=Rotational frequency (RPM/60)
p=pitch
The advance ratio is J=U/nD
U is the freestream velocity in meters per second.Comment
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You need to assume or find out the efficiency your esc ηesc, so you can determine the total power system efficiency that is denounced as ηe.
Lets assume your YGE esc is 85% efficient arbitrarily so ηesc=.85 😂 but seriously you can also find this number definitively.
ηe = ηm-ηesc
Power Loading is used as the measure of efficiency for the contra rotating propellor systems.
PL= T/Pm = T/ηevi
Pm = minimum power
"The power loading provides a comparison basis of different propulsion systems in terms of absolute values of minimum power required to produce a given amount of total system thrust."
Longfei Zhao and Sergey Shkarayev
(PDF) Characterization of ducted contra-rotating propeller propulsions (researchgate.net)Comment
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So now that you have read what the Drs have to say ask yourself if you are running this off 2 separate inverters are they tuned correctly for zero roll? Is the props spacing for optimal thrust and low power consumption right on the drive? and what does it sound like.....The props here look like there is really not alot of spacing Ralph.....🙈🙉🙊
Traction Brother
HubertComment
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In memory of James Allen US Marine and 50 year toolmaker with a masters in mechanical engineering.
Best Friends with Henry Nelson and Ed Kalfus
My mentor and one of the best small 2 stroke engine designers in the world.
James held several world in records in Nitro RC boats with engines and all running hardware built by him.
You need a torque cradle bro....and ask rene to post the amp draw and thrust he generated with this scorpion based drive. How much does it weigh again he never posted that... 😛
I'm in love wit SiC
HubertComment
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Hi Borat! This is how to test that ancient YGE 320's or a smart modern esc's actual efficiency. You can set up a real test bench permanently this wayOriginally posted by Clugh View Post
Or you could just ask and trust the answer from YGE
Ill tap back on you in a few
HubertAttached FilesComment
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Lets redefine motor efficiency to ηm in reference to post # 608 to find total power system efficiency. ηe = ηm-ηesc
ηm = Power output/(Power output + power losses)
The Power losses are stator core losses, rotor eddy losses, and the stator winding losses
Power = (T)(ω)
T= Torque
ω= rotational speed (rad/sec)
Therefore...
ηm = (T)(ω)/((T)(ω) + stator core losses + rotor eddy losses + stator winding losses)Comment
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Just in.....Attached FilesComment
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Hi Dr Okon,
Sorry you have been waiting for more answers since 11:28 EST.
So check this out.
A static stand like this tells you nothing really but how much your motor consumes... To me its useless.
and the unilog from it for nothing but estimates of mechanical output. In itself the way you use it doesn't record the actual torque, rpm, thrust, or temperature in several places, like the windings, case, and iron, so what good is it?
You have all these power output numbers off mathematical estimates taken from the input side draw and unilog? so where is your real dyno measuring the true mechanical output?
MHZ's 7455's 20kW for 7 newton meters is not that good at all. He is also one of the heaviest outrunners you can find. I guess you can shave the water cooled base off with the lathe.....🤣
YT
HubertAttached FilesComment
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Did not you know you can build and calibrate a fairly accurate mechanical record of events from 2 high quality RC servos and a photo op?
So I don't really understand what's going on there where you are at.
TTYL,
HubertComment
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