I. Introduction
As the power core of drones, motors directly impact flight safety and operational efficiency. Motor overheating is a common fault, resulting in reduced power output at best, and at worst, coil burnout leading to crashes. This article analyses the causes from mechanical, electrical, and environmental perspectives.
II. Analysis of Core Causes of Motor Overheating
(1) Abnormal Mechanical Load
1. Improper propeller selection / installation
- Excessive pitch and oversized diameter: resulting in a surge in motor output torque, doubling of current, and heightened copper losses leading to increased heat generation.
- Propeller eccentricity / looseness: During rotation, it generates alternating loads, increases bearing friction, and simultaneously induces airframe resonance, leading to localised temperature rise.
- Blade damage / Dust accumulation: Aerodynamic imbalance causes additional load on the motor, obstructing the cooling air duct.
2. Bearing Wear and Seizure
- Bearing oil deficiency, ingress of sand or ageing: increased rotational resistance, with mechanical friction contributing a greater proportion of heat generation.
- Motor shaft bending / axial movement: Uneven clearance between rotor and stator causes ‘sweeping’ phenomenon, generating localised friction heat.
3. Abnormal installation clearance
- Loose motor mount: Vibration causes friction between the stator and motor arm.
- Excessively small air gap between rotor and stator: Generates additional electromagnetic attraction losses during high-speed rotation, accompanied by localised overheating.
(2) Electrical System Malfunction
1. Power supply system malfunction
- Excessive battery voltage drop: Aged batteries and those with low discharge rates cannot meet peak current demands, resulting in unstable motor input voltage and increased copper losses.
- Poor circuit contact: Oxidation of plug contacts and insufficient conductor cross-sectional area cause resistance losses, leading to localised heating that is transmitted to the motor.
2. ESC (Electronic Speed Controller) parameter mismatch
- Aggressive throttle curve settings: Frequent rapid acceleration and sudden braking cause sharp surges in motor current;
- Excessive braking force: During deceleration, the motor generates electricity in reverse, preventing effective energy dissipation and causing coil overheating.
- Excessively low drive frequency: At low frequencies, motor commutation losses increase, causing temperatures to rise rapidly.
3. Quality defects inherent to the motor itself
- Coil winding defects: damage to the enameled wire insulation layer (short circuit), turn count deviation, resulting in abnormal copper losses;
- Magnetic demagnetisation / installation misalignment: Uneven air gap magnetic field, fluctuating electromagnetic torque, increased additional losses;
- Defective heat dissipation structure design: Insufficient surface area of the external heat sink fins; internal air ducts obstructed.
(3) Environment and Operating Conditions
1. Effects of Ambient Temperature
- Operating in high-temperature environments: Reduced thermal differential hinders effective dissipation of motor heat;
- Dust / Humidity Exceeding Standards: Dust accumulation on heat sinks and coil dampness reduce thermal conductivity efficiency.
2. Flight condition overload
- Prolonged full-load operation: Continuous high-power output from the motor results in cumulative heat generation exceeding the thermal dissipation threshold.
- Violent flight manoeuvres: frequent climbs, high-speed turns, with instantaneous motor load peaks exceeding design thresholds.
III. Diagnosis of Overheating
Rapid diagnostic method
- Temperature monitoring: Immediately after flight, inspect the motor casing using an infrared thermometer.
- load test: Run unloaded for 3 minutes; if the temperature continues to rise rapidly, it is highly likely an electrical fault. If overheating occurs under load, prioritise checking the mechanical load.
- Phenomenon Correlation: Accompanied by vibration → Eccentricity / bearing issues; Power reduction → Battery / ESC compatibility issues; Persistent high temperatures → Heat dissipation / coil issues.
IV. Conclusion
Overheating in drone motors arises from multiple overlapping factors, with the core operational principle being ‘prevention first, precise troubleshooting’: standardised selection and installation, regular maintenance of mechanical components, optimisation of electrical parameters, and appropriate control of flight conditions can effectively reduce overheating risks. It is recommended to establish a maintenance log, recording post-flight motor temperatures and operating conditions, and to develop a personalised maintenance schedule. This approach safeguards motor stability at its source and extends the drone's operational lifespan.