Scorching motors are some of the frequent points in FPV drones. They’re warning indicators that one thing isn’t proper along with your quad, generally accompanied by trilling oscillations and vibration. Whereas heat motors after an intense flight are regular, excessively scorching motors can result in decreased efficiency, broken motors, and even a mid-flight crash. On this article, I’ll clarify why FPV motors get scorching, what usually causes it, and methods to repair it.
Why Are Scorching Motors Dangerous?
- Scorching motors result in scorching magnets, which may trigger demagnetization and cut back motor effectivity and energy.
- Some forms of magnets might have higher warmth resistance than others, however magnets can nonetheless lose magnetic energy over time resulting from fixed overheating.
- When motors get too scorching, the enamel coating on the motor windings can soften, inflicting electrical shorts contained in the motor and completely damaging it.
- Power can be wasted as warmth, which ends up in shorter flight time.
Methods to Inform if Your Motors Are Too Scorching
Pinch the motor bell along with your fingertips after a flight. When you can’t maintain your fingers there comfortably for various seconds, the motors are too scorching.
Why Motors Get Scorching
At a excessive degree, motors warmth up when electrical power will not be effectively transformed into mechanical movement.
- If the motor spins freely: electrical power → kinetic power → minimal warmth
- If the motor is resisted or compelled to combat itself: electrical power → warmth
So in actual flight, when the motors look like spinning usually, why do they nonetheless overheat?
Fashionable flight controllers continuously alter motor RPM to stabilize the drone. Ideally, these changes are easy and keep inside what the motor can bodily obtain. However when instructions change quicker than the motor can reply, issues happen.
Motors have mass and inertia, which suggests they can not immediately velocity up or decelerate. If the flight controller sends extraordinarily speedy modifications, the motor finally ends up combating these instructions.
The consequence:
- Present surges forwards and backwards via the windings
- Power is dissipated as warmth as an alternative of movement
- Motor temperature rises
- Inside electromagnetic losses improve
Although the motor seems to be spinning usually, it might really be underneath quite a lot of inner stress.
Too A lot D-Time period, Too Little Filtering, or Each
Whereas many components can contribute to scorching motors, suboptimal PID tuning and filter tuning are in all probability some of the frequent causes in FPV drones.
Unsure what PID is? Try this newbie’s information: https://oscarliang.com/pid/
D time period is important for easy flight. It helps dampen overshoot and cut back prop wash. However it’s also one of many main causes of motor overheating. You need simply sufficient D acquire to get good flight efficiency, however not an excessive amount of that it creates extreme noise and warmth. That’s the reason correct PID tuning is essential.
I’ve a complete weblog publish that explains this in additional element right here: https://oscarliang.com/excessive-d-gain-cause-oscillations-motor-overheat/
In a nutshell, D-term amplifies high-frequency indicators. That is helpful for damping oscillations, however it additionally amplifies noise. If noisy gyro knowledge enters the PID loop, D-term boosts it and sends these speedy fluctuations to the motors, and it turns into a suggestions loop which makes the issue worse. The motors then obtain instructions they bodily can’t observe.
End result: warmth.
The overall strategy ought to be:
- Configure filtering correctly first, to attenuate latency whereas sufficiently cut back noise earlier than it reaches the D-term calculation
- Use applicable amoutn of D-term filter settings
- Enhance PID features solely till it begins turning into too noisy
- When you don’t know what you’re doing, simply stick to Betaflight default
Listed below are the tutorials explaining methods to tune PID and filters:
Methods to Repair or Stop Scorching Motors
To diagnose the problem, carry out related brief take a look at flights. Ensure you fly the identical path and use roughly the identical throttle in each take a look at, so the comparability is significant.
30 seconds to 1 minute at 50% to 70% throttle is an efficient start line.
New Propellers
Step one in troubleshooting scorching motors is to alter the props. Typically the blades could also be bent and it isn’t very apparent. When you have beforehand had profitable flights with a selected sort of propeller, begin there. Ensure you should not utilizing propellers which can be too giant or have a pitch that’s too excessive, as this could put extreme load on the motors.
Examine and Safe All Elements
The subsequent factor to examine is how securely all of the elements are mounted and whether or not all screws are correctly fixed. Ensure that the body, digicam, and FC stack are all safe and that there aren’t any free screws. On the identical time, don’t over-tighten the FC stack nuts — depart a little bit room for the mushy mounting to do its job.
Additionally be sure that there aren’t any dangling wires that might probably hit the FC or gyro throughout flight, inflicting vibrations. Safe all wires with zip ties.
Verify the Motors
Are the motor screws touching the motor windings as a result of they’re too lengthy? Methods to examine: https://oscarliang.com/check-motor-screws-touching-winding/
Then proceed to open the Motors tab in Betaflight Configurator. Take away all propellers first, plug in battery, then spin every motor and search for variations by checking the gyro traces within the configurator. This may also help you identify whether or not a selected motor is noisier and inflicting extra vibration than the others.
It is usually potential that one motor is defective. For instance:
- the bearing could also be worn out or broken
- the motor bell / magnets could also be scraping the stator resulting from a bent shaft
- the motor bell could also be unbalanced
48kHz ESC PWM Frequency
Utilizing 48kHz PWM frequency in your ESC settings might cut back braking energy barely, however it may make motors run smoother and cut back motor warmth.
Utilizing AM32 ESC? Listed below are my advice settings: https://oscarliang.com/best-am32-settings/
Use Extra Conservative PID and Filter Tunes
An aggressive tune with too little filtering usually results in scorching motors. When you begin getting scorching motors after altering PID or filter settings, it’s best to roll these settings again.
The default settings in Betaflight are pretty conservative and customarily work properly throughout a variety of fashions. You shouldn’t usually get extreme oscillations or scorching motors with the inventory tune, no less than on 5-inch and smaller quads anyway. After getting confirmed that the default tune doesn’t produce scorching motors, you possibly can start tuning extra aggressively, one setting at a time.
The important thing questions are:
- Is D acquire too excessive?
- Did you cut back filtering an excessive amount of?
If you’re nonetheless getting scorching motors with the default PID and filter settings, that could be a robust signal the issue could also be mechanical, similar to poor construct high quality or a defective part.
Add Extra Capacitors
When you shouldn’t have a capacitor soldered to the ESC energy pads but, it’s best to.
If you have already got one, strive utilizing a bigger capacitor or including an additional one for extra capacitance. This will assist cut back electrical noise reaching the gyro, which may contribute to vibrations and unstable motor conduct.
Capacitors are by no means too many, so long as you’ve gotten the house for it.
I’ve a tutorial explaining why, what and the place it’s best to use capacitors: https://oscarliang.com/capacitors-mini-quad/
Ultimate Ideas
A well-performing quad ought to fly easily, effectively, and land with motors which can be cool or solely barely heat — not scorching scorching. Every time electrical power will not be effectively transformed into movement, it turns into warmth. The trigger could be hardware-related or software-related, so you want to work via a guidelines to search out the true supply of the issue.
Both method, a scorching motor is dangerous. It hurts efficiency, can harm the motors, and will even result in failures in flight. That’s the reason it is very important repeatedly monitor motor temperature and deal with scorching motors earlier than they change into an even bigger situation.
Edit Historical past
- Feb 2023 – Information created
- Could 2026 – Up to date
