Scorching motors are one 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 sizzling motors can result in decreased efficiency, broken motors, and even a mid-flight crash. On this article, I’ll clarify why FPV motors get sizzling, what usually causes it, and the right way to repair it.
Why Are Scorching Motors Dangerous?
- Scorching motors result in sizzling magnets, which may trigger demagnetization and scale back motor effectivity and energy.
- Some kinds of magnets could have higher warmth resistance than others, however magnets can nonetheless lose magnetic energy over time as a result of fixed overheating.
- When motors get too sizzling, 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.
The right way to Inform if Your Motors Are Too Scorching
Pinch the motor bell along with your fingertips after a flight. For those who can’t maintain your fingers there comfortably for various seconds, the motors are too sizzling.
Why Motors Get Scorching
At a excessive stage, 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 battle itself: electrical power → warmth
So in actual flight, when the motors seem like spinning usually, why do they nonetheless overheat?
Trendy flight controllers continually modify motor RPM to stabilize the drone. Ideally, these changes are clean and keep inside what the motor can bodily obtain. However when instructions change sooner than the motor can reply, issues happen.
Motors have mass and inertia, which implies they can not immediately pace up or decelerate. If the flight controller sends extraordinarily speedy modifications, the motor finally ends up combating these instructions.
The end result:
- Present surges backwards and forwards by means of the windings
- Power is dissipated as warmth as an alternative of movement
- Motor temperature rises
- Inside electromagnetic losses improve
Regardless that the motor seems to be spinning usually, it could really be below lots of inner stress.
Too A lot D-Time period, Too Little Filtering, or Each
Whereas many elements can contribute to sizzling motors, suboptimal PID tuning and filter tuning are in all probability one of the frequent causes in FPV drones.
Undecided what PID is? Try this newbie’s information: https://oscarliang.com/pid/
D time period is crucial for clean flight. It helps dampen overshoot and scale back prop wash. However it’s also one of many major 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 vital.
I’ve a complete weblog submit 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 alerts. That is helpful for damping oscillations, but it surely additionally amplifies noise. If noisy gyro information 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 not comply with.
Outcome: warmth.
The final strategy ought to be:
- Configure filtering correctly first, to reduce latency whereas sufficiently scale 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
- For those who don’t know what you’re doing, simply follow Betaflight default
Listed here are the tutorials explaining the right way to tune PID and filters:
The right way to Repair or Forestall Scorching Motors
To diagnose the problem, carry out comparable quick check flights. Be sure you fly the identical path and use roughly the identical throttle in each check, so the comparability is significant.
30 seconds to 1 minute at 50% to 70% throttle is an efficient place to begin.
New Propellers
Step one in troubleshooting sizzling motors is to vary the props. Generally the blades could also be bent and it isn’t very apparent. If in case you have beforehand had profitable flights with a specific kind of propeller, begin there. Be sure you usually are not utilizing propellers which are too giant or have a pitch that’s too excessive, as this will put extreme load on the motors.
Examine and Safe All Elements
The subsequent factor to verify is how securely all of the elements are mounted and whether or not all screws are correctly mounted. Ensure that the body, digital camera, and FC stack are all safe and that there are not any free screws. On the identical time, don’t over-tighten the FC stack nuts — go away slightly room for the delicate mounting to do its job.
Additionally be sure that there are not any dangling wires that might doubtlessly hit the FC or gyro throughout flight, inflicting vibrations. Safe all wires with zip ties.
Examine the Motors
Are the motor screws touching the motor windings as a result of they’re too lengthy? The right way to verify: 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 help you identify whether or not a specific motor is noisier and inflicting extra vibration than the others.
Additionally it is 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 as a result of a bent shaft
- the motor bell could also be unbalanced
48kHz ESC PWM Frequency
Utilizing 48kHz PWM frequency in your ESC settings could scale back braking energy barely, however it could make motors run smoother and scale back motor warmth.
Utilizing AM32 ESC? Listed here 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. For those who begin getting sizzling motors after altering PID or filter settings, you must roll these settings again.
The default settings in Betaflight are pretty conservative and usually work nicely throughout a variety of fashions. You shouldn’t usually get extreme oscillations or sizzling motors with the inventory tune, at the least on 5-inch and smaller quads anyway. After getting confirmed that the default tune doesn’t produce sizzling motors, you’ll be able to start tuning extra aggressively, one setting at a time.
The important thing questions are:
- Is D acquire too excessive?
- Did you scale back filtering an excessive amount of?
If you’re nonetheless getting sizzling motors with the default PID and filter settings, that may be a sturdy signal the issue could also be mechanical, comparable to poor construct high quality or a defective element.
Add Extra Capacitors
For those who wouldn’t have a capacitor soldered to the ESC energy pads but, you must.
If you have already got one, attempt utilizing a bigger capacitor or including an additional one for extra capacitance. This may increasingly assist scale back electrical noise reaching the gyro, which may contribute to vibrations and unstable motor habits.
Capacitors are by no means too many, so long as you may have the house for it.
I’ve a tutorial explaining why, what and the place you must use capacitors: https://oscarliang.com/capacitors-mini-quad/
Closing Ideas
A well-performing quad ought to fly easily, effectively, and land with motors which are cool or solely barely heat — not scorching sizzling. At any time when electrical power will not be effectively transformed into movement, it turns into warmth. The trigger might be hardware-related or software-related, so it’s worthwhile to work by means of a guidelines to search out the actual supply of the issue.
Both method, a sizzling motor is unhealthy. It hurts efficiency, can injury the motors, and should even result in failures in flight. That’s the reason it is very important commonly monitor motor temperature and deal with sizzling motors earlier than they turn into a much bigger difficulty.
Edit Historical past
- Feb 2023 – Information created
- Could 2026 – Up to date