RC motors: size, torque, speed, KV, KT - everything you need to know
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- เผยแพร่เมื่อ 26 มิ.ย. 2024
- Support my work / pawelspychalski
Electric brushless motors for drones and RC airplanes. A simple topic, right? OK, maybe if you a few years in the hobby. But if you are only starting, you might have at least a few questions. In this video let's discuss some basic (beginner to intermediate level) aspects of brushless electric (BLDC) motors used in RC hobby to drive drones and airplanes
- how to measure the motor size
- what is KV and how it correlate to rotation speed
- motor torque
- motor KV vs torque - how KV changes torque and how it correlates with another motor constant: KT
- stator and rotor - what is what and it's named like that
- number of coils and poles - 12N14P etc
- does motor care about rotation direction
- how to change the rotation direction of a motor
- mounting holes spacing: 16x19 and 16x16 motor holes pattern
- how not to fry your motor right away
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Pawel; This was a good tutorial. I'm still struggling a bit with what KV motor to use with DIfferent size prop and battery voltage (4S,5S,6S batteries). Can you take us to the next step:
proper motor selection for your #size quad based on Prop size, battery voltage and expected flight time: Race/speed vs freestyle or cinematic style flight times.
Funny thing, I made video about it few months ago th-cam.com/video/HAj_WLJkcZg/w-d-xo.html
@@FPVUniversity I must have deleted it from my watch list just because I saw "7-inch". Watching it now. Thank you soo much!
Paweł Spychalski the linked video was what I needed! Excellent!
i dont mean to be off topic but does anybody know of a tool to get back into an Instagram account?
I was dumb forgot the password. I appreciate any tips you can give me.
@Braxton Makai instablaster ;)
Best video on BLDC theory! 👍👍
It was really helpful for understanding the different stuff about brush less motors for Rc planes. Thank you for the video
Awesome info, Pawel! 😊
Thanks a lot!
Great explanations, you answered questions I didn’t even know to ask. So much detail in a short time, thank you :)
My pleasure
Always useful info
New to RC planes, excellent video
Very nice video. Friendly and informative. Thanks.
Glad it was helpful!
woww thank you
thanks for a nice video, I would like to ask you make a video on how to estimate the trust needed for flight and how to calculate the trust that engine can provide.
Thank you.
Czesc Pawel :) czym zajmujesz sie na codzien ?
Leaving myself a note here: 2:37 is where naming conventions are discussed
what is that wing you got there in the background!? that looks awsome, i want to build one!
Some custom cut 900mm wing. Available only in Poland I'm afraid
Good info. Now just match the pitch to the power curve and you have flight time. And if something can't be touched because it is too hot, there's a problem.
Hi,
I have a doubt that, can't we use flat bldc motors like 5080 , 5060 with 360kv motor and 400kv motors for rc airplanes?
They have high thrust though.
Plzz reply if someone get my point
Thanks
you are welcome
Hi Pawel, very informative. Just one question about motors for a 5'' Qwad... How do I know what size/kV to use in comparison to the battery cell count? I've got a 5'' Qwad with 2206 2600kV motors, thinking of buying a 6S battery to see if the hype is real but can I use a 6S on these motors at all or would I have to buy new motors? If I needed new motors then what size/kV could I use? Is it possible to use 4S and 6S on one and the same motors?
size has to be the same or bigger, nothing changes here. 2600KV equivalent on 6S would be 1750KV. 2600 * 4 / 6
@@FPVUniversity So I need to buy new motors if I wish to try 6S .. thanks for the answer.
@@DogWsd You can try a 66% throttlecut in a pinch. But to get any real advantage of 6s you need motors with KV 66% of the 4s equivalent.
I was hoping you would discuss some of the finer differences between Quadcopter motors and RC plane motors. I am looking for a motor/prop combination that I can use for both applications. What would you suggest?
They are the same motors. The only practical difference is size, how much weight is important and if you want to have longer shaft. But mechanically they are the same
I need a high torque bldc motor can anyone suggest me a good kv or kt rating for that , not quad , for pulling in a zipline retteiver ..... Please suggest.
So if I have a 3660 motor those numbers pertain to the width and length respectively? Thanks for this video!
usually yes. Sometimes the numbers does not match the dimensions though
@@FPVUniversity I got you. So it would be 36mm wide and 60mm long...(roughly) Thanks!!!
It's a peculiar definition or specification of direct current, to the esc not to the motor itself. A bldc "motor" must include the esc, the commutation, to be able to be called bldc because just the motor alone is 3 phase AC. The esc turns a single dc source into three alternating 120 degree out of phase outputs to feed that blac motor
Yup. Motor is just a 3 phase motor. Motor+ESC makes BLDC
You didn't explain what the last number effects and means. Example is 2204/12 where you left out the number of times the wire is wrapped around the stator or whatever.
Video does not describe why some identical size motors are much more powerful than others.
OK, maybe I should... Basically, its about magnet strength, airgap and losses in the stator from eddie currents
The answer is simple. It depends on the:
- how accurate the stator was made
- how accurately the coils were wound
- how big (small) is the gap between the stator and the magnets in the bell
- how strong are the magnets
Some manufacturers use many thin wires combine together instead of thick wire. This allows to place the wire more accurately on the stator.
The tighter coil binding and the smaller the gap is better.
See wiring of these motors. Same size. Different thick of wire.
www.propwashed.com/wp-content/uploads/2017/06/04_windings-1080x675.jpg
Of course, a small wire diameter is not always the best solution. However, thin wires are easier to arrange on the stator.
I'm not an expert in any way. However, I feel safe in saying the more powerful motors use better quality materials in their stator, windings, magnets, probably even better bearings as well.
1:00 "Three phases because we have three wires" - is a non-explanation, a tautology. Three phases is the minimum you get away with to get high efficiency out of this type of motor because you need one inactive phase's back-emf, one phase to "push" away from a magnet and one phase to "pull" towards a magnet.
1:10 "In theory you could plug the motor into 3-phase AC in your apartment and it would spin." - no, it wouldn't. You're confusing BLDC motors with AC motors.
4:40 "kv is the theoretical rotation speed of the motor without any load [given 1V input]" - wrong, even theoretical. You explain it better in the following sentences.
7:30 "kt ~= 10/kv more or less" - is complete nonsense, kt is defined as 1/kv. Exactly.
8:42 "winded" - past tense of "wind" is "wound", I commented the same on your old rewinding videos
13:00 the "natural" direction of rotation is CCW, exactly the opposite of what you show, but you might have moved the shaft and shown the wrong end of the motor
1:10 - BLDC is powered with impulses on right timing. ESC are sensing that right time to trigger impulse. There are no sinusoidal weave! Sinusoidal weaves are on PMSM motors (used on industrial robots, and CNC mostly), where Servo amplifier have seperate encoder to "see" where the axis is.
you see mate, I could go into a long discussion about things, but I will only talk about 2 things: KT is not 1/Kv. It is true in linear motor. I suggest to read more on the topic.
And BLDC is a combination of 3phase motor and an ESC that converts DC to 3 phase approximation.
I do not remember I said anywhere that there is a sine on the ESC output. And especiallu at 1:10 Sine approximation from PWM but not real sine
@@marcinb5607 Both BLDC and PMSM are brushless, permanent-magnet motors. The different is typically in the definition of how the windings are distributed and how the shape of the back emf looks like.
Btw, most "BLDC" motors for RC applications do actually have more or less sinusoidal back-emf for reasons of higher effiency. You can also drive them with sinusoidal three-phase AC. Even the BLDC motors with trapezoidal back-emf.
@@FPVUniversity kt is 1/kv.
kt is literally defined as the back EMF per unit mechanical speed which is the exactl inverse of kv.
This is proven mathematically and physically.
Why don't you tell us what size motor is used to fly different airplanes? That would be useful information. What you shared is basic info that everyone already knows anyway.