What kills an RC Brushless Motor - Current or Voltage
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- เผยแพร่เมื่อ 14 ก.ค. 2024
- Some of us may have experienced an RC brushless motor failure. What makes them fail electrically really only comes down to two parameters. Voltage and Current.
Increasing voltage on a brushless motor simply increases the total amount of output RPM. Further increasing the voltage provided to the motor simply increases the total amount of RPM expected out of the motor. Mechanically you will see a threshold where if exceeded the bearing or rotor will fail. However, electrically voltage does not cause direct harm to the brushless motor.
When looking at current, we can directly relate current to the load on the motor. As the load of the motor increases, the current increases. Current in brushless motor windings produces waste heat. Heat ultimately destroys a brushless motor. - วิทยาศาสตร์และเทคโนโลยี
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100% correct, current is the killer as copper wires thickness has specific current rating. Enamel is able to handle voltage in the kilovolts. For example, the 0.375 mm wire with cracked enamel can have a voltage breakdown of 4.35kv despite the enamel thickness being only 0.0275 mm. Similar to the RC technology is electric scooter technology, just bigger (although some RC planes are massive), there are people who aren't happy with the speed they get so they add solder to the controllers busbars and up the voltage to the controller thinking it's clever.
Great knowledge. Thanks for sharing, will pass this on.
Thank you!
Very interrestig and informative! Thanks you Sir!
Good general knowledge about brushless engines and loads. Thanks!
Thank you for the comment K Lemm!
I have a 2200kv motor what batt do I udd[;12³
Nice Explanation! I'm going to share this in a few of the Facebook groups I participate in. Again, I've preached this same message for years, but it's good for guys to get the same message from multiple sources.
Thank you!
this is generally why higher rpm motors such as blenders and power tools (saws grinders, etc) have fans built onto the rotors unlike slower things
Good to know thanks
I over-powered my small dc motor using a dc bench supply. Arcs were crossing over from both wires and it smelled weird lol... To my surprise, the motor still works.
Ooops. sounds like something cooked.
Spot on discription👍
Thank you very much 👊🏽
No problem 👍
I have an Arrma Granite BLX with a stock 3200KV motor that I believe became demagnetized. I didn't change gearing or anything from stock but was running the max battery size, a 3S lipo. The motor is mechanically sound but dead as a door nail as it produces ) power when spinning it with a drill. My question is what replacement motor KV should I get? I don't want more power or speed as it is already a beast. I am ok with being a bit slower or whatever but i need to keep running the 3s as i don't want to buy a whole bunch of new batteries. I was thinking maybe a 2800KV would provide a little more torque but less rpm, which should reduce heat but hopefully not overwhelm the drive train of the car. Does this sound reasonable? Thanks for the video!
Hey thanks again for a very informative video! I’ve got another generator question for ya.
In your other video you showed mathematically how the iron losses were calculated using Io current values. Is that for all output currents or was that just for a no load situation? Thanks again for you time!
Iron losses is calculated using Io of the motor at the motor speed specified. This speed is based on voltage. Spin the motor up to the speed you need it to operate on the generator using an ESC and battery, then measure the Io value.
@@RCexplained thank you! That’s helpful!
@@RCexplained i have an aircooled brushless motor with big fins meant to act as heat sinks for air
I was thinking about converting the motor cover with the fins run water on the fins
Wouldnt this allow me for example to run more current
As long as the temperatures do not exceed the what they are supposed to be i can keep adding current to find the new continious rating
Hi
Great video very informative. Just a question what temperature would still be safe before you risk to demagnetize the rotor?
This would be the maximum safe operating temperature specification as provided by the manufacture of the motor. Temperatures can vary significantly from manufacture to manufacture based on the quality of the magnets used in the rotor.
Very helpfull thanks
Thank you for your comment!
I'd like to know for hm brand bldc 3phase motor, they dont have data sheet for this so for 72v motor, they have 3kw,3.5kw,4kw motor and so on for this specific voltage.
How do they determine the wattage for this 72v motor when the awg wire are all the same?
Could you please look at their motor, which awg wire they are using and so what is the maximum safe current to use on this cable and motor too. I've a few questions for this. Appreciate your help👍👍
very nice
What about a small 12 volt compressor? I did the air horn drill mod which runs off a 18 volt battery and drill body and I’m wondering if the compressor will burn out due to the voltage
motors don't burn out due to voltage. Voltage can indirectly burn the motor out by increasing current.
Nice!
Thanks!
I wish someone would answer this.
If I run a 1800kv motor on 8s & achieved +55000rpm based on multiplying , what average percentage of rpm is lost once the motor is under load? Specifically to Rc boats & speed runs. I know prop size is a big factor, but there's always the perfect prop for each boat. I'm curious what rpm a boat would see vs what the math says rpm is w/o load
I've included a section in the RC calc sheet that covers this on calculations done for RC Cars. You can find this on the Patreon link in the description.
The RPM lost while under load depends on how loaded the motor is. The more aggressively loaded the motor is, the higher the percentage of RPM loss.
Brilliant explanation! But, could you please show an example of motor current and resistance probing? Thank you!
Hi milesw7, thank you for your comment. What were you looking to get out of the motor current and resistance probing?
Thanks a lot
No Problem!
Nice video 👍😏
Glad you liked it
Nice. My motor overheated on my xmaxx 8s the other day. Could my loose connection from one of the ESC and batteries have helped the demise? The xt90 connector there got hot and turned black both on the ESC side and battery side! I saw smoke coming out of the motor. Thanks.
Hi Rc enthusiast, with a loose connection my concern would be in radio power dropouts. Was only one of the batteries connectors over heating? Or was it both batteries?
Generally when I see a motor that is very hot and also a battery connection that has over heated, the power system was just pulling too much power for what it was designed for. A poor connection, not necessarily a loose connection would rob power being sent to your motor. The connection point may be hot, but the motor is seeing less power and heat.
@@RCexplained I had just installed slightly bigger tires and gearing that has worked well for other xmaxx 8s owners. My motor fan had stopped working, so I think it was a combination of those things. Yeah I did have my temperature gun with me but I was too excited to just jump and run my vehicle hard after installing a new motor mount, 20/50t gearing and bigger tires.
Has anyone tried a 3s with a hacker a10 12s motor? Its recommended to be used with 4.5x4 prop on 2s, but i would like to try it with 4x4 or 3x3 prop on 3s.
So I bought a 3s 1600 mah 11.1v for my hobbywing 1/18 7800kv motor and it has the hobby wing 18a motor will I be ok to run that battery?
That motor would be too much kv for 3s LiPo. My preference would be 2s LiPo.
RCexplained ok thank you
Hi, what's the difference between current and voltage, please?
I think your videos are very good :D
Thanks for the information too
(Im sorry)
Thanks Dafhatas and no worries!
Very nice vid! I have 2845 3100kv motor with max
I would not go above the esc limit.
@rcexplained so the simple tip is to just keep increasing voltage and not the amps.
btw quick question What has an effect on Torque? amps or voltage? or both? I feel my electric motor could do more uphill climbs but perhaps I should increase the voltage?
A total combination of 2 things have an effect on torque. That is current (amps) and the motor constant kt (inverse of kv).
Here is the catch, and often confusing to understand at first. If you increase voltage and all else remains the same, (**provided your system can handle the increase**) current output will also increase. This is because the overall load on the motor will be higher as you are demanding the motor to work harder. Load and Current go hand in hand.
You can reduce maximum pwm output to offset the increase in voltage for a similar total maximum watt draw. You can program it on some ESCs, and can do it if using a flight controller with betaflight etc, some radios can do it. Opentx radios etc.
More voltage but same total watts is more efficient, less resistance since lower current. Higher kV motors have thicker wires and shorter wires (less turns) and offer lower resistance, so using high KV with high voltage is a good way to get efficiency if you manage to limit it like above or another method etc.
Since it’s more efficient and less resistance over all, you can likely have a higher watt draw and power output overall for the same heat output with lower voltage and lower kV.
Thank you for the comment Daniel!
Thanks for the video. What I'm getting out of this is that I just need to make sure the RPM on my motor is no higher than the rating or what it was before the voltage jump and to give respect to the thermal requirements. Am I getting that right? I watched your videos enough to know how to calculate the RPM based on the KV rating and voltage battery.
That is right, all motors have a maximum rate RPM that you must not exceed. Too high of a voltage can exceed these mechanical limitations.
Paying respect to the thermals of the motor will keep the current in check.
@@RCexplained Thanks Ryan. Still loving your videos. I feel like I'm messaging a celebrity.
@@bdubq3653 That's awesome that you enjoy the videos. I'm not celebrity, just a dude who loves RC!
Quick question
Can I run a 12v 0.6A rated cooling fan on a 12.6v 12A power supply or will it smoke up?
It's OK.
The current rating of the constant voltage power supply is the maximum it can deliver, not what will flow.
Good video
I have a question if i want to get more power and not getting heat motor is 12 volt it's starter motor i want to rewind it i fund the previous turns is 15 turns can i make it with the less guage ex 0.5 mm wire and what the appropriate turns my battery is 12v 55 ah as we know starter motor designed to run for short time i want to rewind it to run for long time at the same time not getting heat?
More turns of thinner wire
Is more turns and thinner wire effects speed?
Imean if i increase turns and decrease wire to thinner that's mean need more current or more voltage to get speed and torque?
And thanks for answering 😘
More voltage. Power will be limited by heat.
do brushless motors go bad when esc catches on fire?
When you say the "CURRENT" are you talking about the WATTS, i.e. AMPS x VOLTAGE, or something else?
current is measured in amps.
Hi thank you for your video.
So how about this scenario for a plane..
You go from a 3s setup to a 4s setup. keep the prop the same.
So naturally the higher voltage would cause the same kv motor to spin faster, drawing more amps.
However what if the maximum wattage is limited? so lets say 12.6v 3s 10amps ... 126 watts.
Bump voltage to 4s but limit it to 126watts (limit at 7.5amps).
Both setups will give the same thrust, but would the 4s setup run the motor cooler as youve dropped the amps? Your current squared × resistance formula would say yes it will run cooler. Right?
Thanks
Hi Mark, interesting thought. I think there's a couple more variables to consider. How would you limit power to 126 watts? Is this governor 100% efficient, odds are it's not. A motor limited by partial throttle is seeing less voltage in order to reduce the overall maximum RPM.
@@RCexplained Hey, sorry for the delay in replying. Ah right well I guess i better go back to the basics then, i was using my fc to limit the watts.
For some reason I thought that the esc would send shorter pulses of higher voltage to the motor.
thanks for the great video, have a question please, can i use 120A esc on a brushless motor rated 70A max? thank you
Hi Fred, yes you can. Just make sure that the RC you plan to use these components in do not draw more than 70A max.
@@RCexplained thanks for the respond, using main gear of 64T with 21T motor gear, on 1/10 truck, not sure if I’m at the safe zone, if I’ll use 60A will I lose noticeable performance? Thanks
Hey I have something interesting happening that maybe you could explain:
I’m encountering a problem that I would love your help with:
I have a brushless DC motor rated (1.5v to 9v).
I’m feeding a range from 3.36v to 3.95v (see the video, wiring diagram, and motor specs below)
At seemingly random times, once the motor is turned off, it will not turn back on again. It doesn’t seem to correlate with how long it was last run, or the load it had. It never stalls while spinning, only once turned off.
The only pattern I can start to gather after hours of experimenting is that if it happens to stop spinning and the shaft is in a certain position, the likely hood of it starting back up, goes down drastically. There are two shaft orientations that seem to be a hang up. But…. Not always. Not every time the motor stops in those orientations does it stall. Only sometimes. The inconsistent nature and lack of pattern in this problem has me baffled.
The severity of the stall too, seems to be inconsistent. Sometimes to get the motor going again I only need rotate the shaft slightly our of the stall orientation and then apply power. Other times, this will not work and I have to apply power and manually rotate the shaft for several gentle but quick spins before the motor will begin to spin on it’s own. Other times I have to apply power and spin the shaft manually very quickly for 20 or more rotations before the motor will spin on its own, and it’s not an immediate take over… the motor will start to spin slowly and gradually accelerate to full speed.
Any ideas at what is causing this? This project is for a Halloween party I am throwing, and I plan to make 8 or so of these particular gadgets, but they need to work reliably without manually having to manipulate the motor in order to get it to work.
I would love any insight you might have. I am brand new to small electronics.
Here is the exact motor I am using:
smile.amazon.com/dp/B07Q44YYKG?psc=1&ref=ppx_yo2_dt_b_product_details
Here is the motor issue live in a video:
www.loom.com/share/bbf8b3978e2a49cea628d1a052894829
Here is my wiring diagram:
drive.google.com/file/d/1JgbZNAn3SsPm2d0HUFM-ipDk4i7HLMN_/view?usp=sharing
Hi Brenton, the motor appears to be brushed and not brushless. Does it spin up correctly in the stuck spots when wired more directly to a power source? Do all the motors in that kit have dead zones? Is there any current drawn when it is "stuck."
Thanks for this. So my understanding is that if I use a 5V motor shield with an Arduino on a 3V motor, as long as I set the code to not spin it at max speed, say 2 thirds max output, then I should be good right?
This is for a brushless motor?
@@RCexplained Actually I don't know. Does it matter?
@@ArcanePath360 To a certain degree yes. Brushed motors will experience more wear when being overdrive. However, you can over drive a motor as long as you stay with in the thermal and mechanical limits of the motor.
@@RCexplained Thank you.
But MGM speed controllers are capable of 55 volts. Will that cause the voltage to jump the wire?
No, it's not that simple.
Hi Ryan. Thanks for the info as always. When manufacturers claim the max current is X amps i suppose they're considering the forced convection from the propeller ? For example, i have a motor with 40A max in delta configuration with 1 strand 0.55mm wire (so 23 A max for each phase). 23A is a lot for a 0.55mm wire if there is no forced convection to dissipate the heat. Regards
Thanks Jean for the comment!
There is no set standard as to what a manufacture is basing a motors maximum thermal limit on. There are many contributors to what that thermal limit would be.
In your example you are assuming the motor is used in an airplane, but how do you or the manufacture make an assumption that I will use that motor in an airplane? What if I place it in to my boat?
I loved it. Perfect lecture, now....... if we have zero load, how many volts/amps could a 2000kv motor hold?
Thank You for your comment. Voltage is dependent on the maximum RPM that the motor can mechanically handle. Total RPM divided by kv will provide you with maximum voltage. Current with no load would theoretically be 0 amps. However nothing is 100% efficient, therefore the current at no load would be equal to the no-load current of the motor. This is denoted by (Io) and can be referenced in the manufactures documentation.
RCexplained ....... thank you for your reply, I just subscribed and on going to enjoy watching all of your videos.
@@AutoBodyEverything Excellent!
Thanks
see if I am right
I want to sacrifice range for speed, so, I can play with voltage and current while I do not exceed the wattage of the motor?
exemple: If I have one 800w brushless motor, and Im using it in 40v 20a(max) daily (with any problems), I could change the controller for one with output 80v and 10a(max) and it will be fine?
and I will just put the 80v10a when the battery is 100% and maximum load on the motor,
something that will not happen very often...
You haven't changed the overall power output. An 800 watt brushless motor will be as fast as an 800w motor. It doesn't make a difference how you get to that 800 watts.
Thanks for the help
@@TheBirells no problem, glad I could help.
Hi. Before whatching this video, I was thinking of the Power instead Current when looking for the limits of any brushless motor, of course, at a given test voltage. I mean, if you go with a 2S LiPo, for instance, the limiting current is way more that that specified for the 3S LiPo battery. Therefore, I thought that you could use a bigger/more power demanding propeller on the motor but with less rpm (with care on not exceeding the limiting power of the motor for certain heat dissipating conditions). I was thinking that part of the power turns into heat, hence the temperature of the motor, of the cooper wires depends on the consumption power instead of the current. Thanks for your explanations.
So I can run a motor rated for 12V on 50V, as long as it doesn't get too hot?
AND it does not exceed the maximum rated RPM for that specific brushless motor.
I wish i had seen this before i killed my motor.. just wondering how will you know if it has affected the esc. My motor just wont turn anymore but esc switches on fine and fan spins🤷🏾♂️
Hi Sean John, my recommendation is to try the ESC out with another motor. You will want to do this in a safe spot in case there are any issues. If your motor burned up and you stopped pressing the throttle quick enough, you will be alright. In my experience, when the ESC goes out, it has been fairly obvious.
@@RCexplained 🤔thats a point it didn't go up in smoke and seems to be ok using another motor.. maybe i just saved it when i noticed it was overly hot.. 👊🏾🇬🇧
@@east_ldnrc1378 Sounds like that is true, you may have saved it. When you run your RC next time, make sure you make the correct adjustment to reduce the load on the system.
Thank you. This is very informative. How much can you bump the voltage, twice as much? for max load.
You can increase the voltage until you hit max RPM of the motor.
RCexplained but i thought it had to do with amps and load? do you mean the rpm with no load? thats not even 36v on my 24v motor, another guy used 24v motor with 48v and has been using it for over a year. he says just dont let it get too hot. is there any truth to this?
@@bojackson3073 the voltage limit is the maximum RPM of the motor loaded or not. The motors power output limit is based on load. More load is more current which translates in to more heat. Too much load builds too much heat and stresses the motor. You can increase voltage as much as you want as long as you don't exceed the thermal and mechanical limits of the motor.
If you double the voltage, you can halve the amps for the same power draw. If you limit the pwm to 50% you wouldn’t have to change anything else.
What about a sensored motor with hall effect sensors?? don`t that sensors get destroyed with overvoltage?
Hey Sergio, great question. It would be difficult to electrically destroy those sensors as the ESC is responsible for them. The sensors circuit is different then that of the primary circuit running power to the motor.
Hello can I run my brushless motor straight to my lipo battery ? Will it hurt anything
Hey Power Plants. Yes that will not work and if you tried it would result in destroyed motor windings.
Got a Titan T50, what are the limits?
What is a Titan T50? Limits would be in the spec sheet.
So is this the same for brushed motors?
It is different for brushed motors. Higher voltage in the brushes can destroy them very quickly.
i m trying to get more torque, is that the same thing
torque comes from current
@@RCexplained isn t current, voltage times amps?
what brand make the most efficient motors?
I haven't run tests to determine the motor with the best efficiency.
@@RCexplained ok any recommendations?
Castle motors are good if this is for a car.
There's unfortunately not enough data out there. With that said, as long as you avoid the super cheap junk you'll probably get a decently efficient motor.
I don't understand english 😭
I have a brushless motor that has 3300kv. what is the maximum voltage the motor can accept?
Work this out from the maximum RPM that the motor can reach according to the manufactures specification sheet.
@@RCexplained Means it must be in accordance with the manufacturer's specification sheet? What if the voltage is forced more than that? On the 15volt max specification sheet, if I give 23volt will it burn? But with the note esc already support 23volt.
@@zhagorazy4628 Voltage does not destroy a motor. Current does. Increasing the voltage can increase the current, it's important to keep this in mind.
If the maximum voltage is 15v, 23v may exceed the mechanical limits of the motor.
@@RCexplained Means that if the use is not too long the possibility of the motor will be okay? and with the addition of this voltage will the maximum rpm increase?
@@RCexplained I have read other comments. so the point is that any voltage will be safe. the problem is the physical load of the motor. the maximum friction and heat that can be received by the motor?
Propeller size should be factored in also.
The content of the videos is really interesting and helpful but it's really hard and frankly boring to watch without any visual aid.. (picture, video etc)
Hi Hariklia Panteli, thanks for the comment. I agree with you and have made improvements to more recently released videos with more improvements to come. This particular video is 2 years old.
They can jump😕😬 I dnt wanna use one now
So how we control ? How can we raise the volt and keep the amp low ? Is there a type of electronic board for that ?? Please
Raise the voltage and at the same time decrease the load. Reducing the load will drop the current. Continue reducing the load until you get the current draw you are after.
I think the correct approach would be in effective gearing. It's used all over the world in real cars from shit boxes to super cars. The potential is real.
Gearing is good
I completely disagree, how could current be the determining factor of the motors failure by increasing the voltage? You just said, you are increasing the voltage only?
Motors electrically fail by heat. Too much current is what produces excessive heat. Voltage does not produce heat.
If you increase voltage only and you have not changed gearing or a prop, the higher voltage will end up increasing current. The increased current is again what ultimately destroys the motor. One could simply operate at that higher voltage but change the load by reducing the pinion gear tooth count or reducing prop size. This would manage the current draw thus heat.
Current!
you got it!
😊
current
"Currernt"
You are so far off on your lecture. The amount of heat that is required to demagnetize the magnets is pretty high.
You won't spin the motor fast enough to cause the rotor to fly apart, if this happens it's a completely crappy motor!
Heat is a byproduct of inefficiency.
The amount of voltage required to "jump" (also called a short)across the windings is in the 1,000 of volts and this will never happen in a BLDC it shouldn't even have been brought up.
Not a hater but please get a solid understanding of what your talking about before you make videos and deceive people with false info.
What destroys a BLDC is when you have a stall in it and you're throwing so much current at it and it can't turn and so the hall sensors won't allow the field windings to switch because the rotor hasn't moved, hence why they have senseless motors so the field windings are constantly switching and the rotor is "skipping" until the stall is gone and the rotor can turn freely. This is the exact same reason a brushed motors burn up. If you're burning up brushless motors you have too small a motor for the load being placed on it.
The only thing I don't like about BLDC is the inefficiency of the switching. I wish it was at the same level as commutator, but unfortunately MOSFET tech isn't quite there yet, hence why controllers get hot...all that switching....
I want to know,
Lets say that i have a max 100a motor, and a 130a esc, and lets say that i have the right cooling so the motor runs at a reasonable temp, would any problems occur?
Hey Dafhatas. I'm not sure where you are going with this, however with the limited information you have provided, no I don't see a problem. Perhaps, if I think I know what you are after this video may help: th-cam.com/video/LTlVWYSexBI/w-d-xo.html
First, thank you for commenting :D
I asked it because,im going to get
A hobbywing seaking 3180kv 3360SL brushless motor, and its max 94A, and i Just cant find an esc for it. I even asked it in forums, but that didnt kinda Work. Do you know the right esc for it? (also it says 16.8v in the Hobbywing site,but it says 18v in the website that i Will purchase it.)
@@-dafhatas-6519 what will the motor be placed in to? How many cells do you plan to run
Well i dont know, as im new to rc.
I Just want it to be right, 16.8v and 94a
(its 16.8v probably)
What do you recommend?
Where is this motor going to be used? Which exact RC?