Sizzling motors are some of the widespread points in FPV drones. They’re warning indicators that one thing isn’t proper together 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 lowered 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 how you can repair it.
Why Are Sizzling Motors Unhealthy?
- Sizzling motors result in scorching magnets, which might trigger demagnetization and scale back motor effectivity and energy.
- Some forms of magnets might have higher warmth resistance than others, however magnets can nonetheless lose magnetic power over time as a result of 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.
- Vitality can be wasted as warmth, which ends up in shorter flight time.
Tips on how to Inform if Your Motors Are Too Sizzling
Pinch the motor bell together with your fingertips after a flight. Should you can’t maintain your fingers there comfortably for various seconds, the motors are too scorching.
Why Motors Get Sizzling
At a excessive degree, motors warmth up when electrical vitality isn’t effectively transformed into mechanical movement.
- If the motor spins freely: electrical vitality → kinetic vitality → minimal warmth
- If the motor is resisted or compelled to struggle itself: electrical vitality → warmth
So in actual flight, when the motors look like spinning usually, why do they nonetheless overheat?
Trendy flight controllers consistently 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 implies they can not immediately pace up or decelerate. If the flight controller sends extraordinarily speedy adjustments, the motor finally ends up preventing these instructions.
The consequence:
- Present surges backwards and forwards by means of the windings
- Vitality is dissipated as warmth as a substitute of movement
- Motor temperature rises
- Inside electromagnetic losses enhance
Regardless that the motor seems to be spinning usually, it could truly be below plenty 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 most likely some of the widespread causes in FPV drones.
Unsure what PID is? Take a look at this newbie’s information: https://oscarliang.com/pid/
D time period is important for easy flight. It helps dampen overshoot and scale back prop wash. However it is usually one of many main causes of motor overheating. You need simply sufficient D achieve 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 necessary.
I’ve a complete weblog put up 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, nevertheless it 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’t observe.
End result: warmth.
The overall strategy must be:
- Configure filtering correctly first, to reduce latency whereas sufficiently scale back noise earlier than it reaches the D-term calculation
- Use acceptable amoutn of D-term filter settings
- Improve PID positive aspects solely till it begins turning into too noisy
- Should you don’t know what you might be doing, simply follow Betaflight default
Listed below are the tutorials explaining how you can tune PID and filters:
Tips on how to Repair or Forestall Sizzling Motors
To diagnose the difficulty, carry out related brief take a look at flights. Be sure 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 effective start line.
New Propellers
Step one in troubleshooting scorching motors is to vary the props. Generally 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. Be sure you will not be utilizing propellers which might 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 test is how securely all of the parts are mounted and whether or not all screws are correctly mounted. Ensure the body, digicam, and FC stack are all safe and that there are not any free screws. On the similar time, don’t over-tighten the FC stack nuts — depart a little bit room for the gentle mounting to do its job.
Additionally be certain that there are not any dangling wires that would 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? Tips on how to test: 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 will help you establish whether or not a selected motor is noisier and inflicting extra vibration than the others.
Additionally it is doable 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 might scale back braking energy barely, however it might make motors run smoother and scale 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. Should you begin getting scorching motors after altering PID or filter settings, you need to roll these settings again.
The default settings in Betaflight are pretty conservative and customarily work nicely throughout a variety of fashions. You shouldn’t usually get extreme oscillations or scorching motors with the inventory tune, a minimum of on 5-inch and smaller quads anyway. After getting confirmed that the default tune doesn’t produce scorching motors, you may start tuning extra aggressively, one setting at a time.
The important thing questions are:
- Is D achieve too excessive?
- Did you scale back filtering an excessive amount of?
If you’re nonetheless getting scorching motors with the default PID and filter settings, that may be a sturdy signal the issue could also be mechanical, corresponding to poor construct high quality or a defective element.
Add Extra Capacitors
Should you don’t have a capacitor soldered to the ESC energy pads but, you need to.
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 might contribute to vibrations and unstable motor habits.
Capacitors are by no means too many, so long as you might have the house for it.
I’ve a tutorial explaining why, what and the place you need to use capacitors: https://oscarliang.com/capacitors-mini-quad/
Closing Ideas
A well-performing quad ought to fly easily, effectively, and land with motors which might be cool or solely barely heat — not scorching scorching. Each time electrical vitality isn’t effectively transformed into movement, it turns into warmth. The trigger will be hardware-related or software-related, so you should work by means of a guidelines to search out the true supply of the issue.
Both method, a scorching motor is unhealthy. It hurts efficiency, can injury the motors, and will even result in failures in flight. That’s the reason it is very important often monitor motor temperature and deal with scorching motors earlier than they grow to be an even bigger subject.
Edit Historical past
- Feb 2023 – Information created
- Could 2026 – Up to date