How to choose the appropriate size of drone motor.
For drone manufacturers and integrators, the choice of propulsion system is a key engineering decision that determines the success or failure of the drone. Choosing the correct size of the drone motor will directly affect flight stability, efficiency, and payload capacity. There is a risk of overheating and malfunction if the system does not match. This guide provides technical analysis for selecting the best motor specifications to meet strict industrial and professional requirements.
Understand the specifications of drone motors
To choose the best propulsion device, it is necessary to first interpret the standard terminology used in the industry.
1. Motor size annotation (stator size)
The motor size is usually represented by four digits, such as 2212 or 5010. This code refers to the stator size, not the external dimensions of the motor casing.
The first two digits (e.g. 22) represent the stator diameter, measured in millimeters. The wider the stator, the greater the torque typically generated, allowing the motor to drive larger propellers more efficiently.
The last two digits (e.g. 12) represent the height of the stator, measured in millimeters. The higher the stator height, the more copper windings can be accommodated, thereby improving heat dissipation and sustainable power output.
In industrial applications, larger stator numbers (such as 60xx or 80xx series) are typically used to support heavy loads, while small drone motors (such as 14xx or 22xx) are designed specifically for light inspection or cluster drones.
2. Speed constant (rotational speed constant)
KV rated value (RPM/Volt) represents the theoretical speed of the motor for every 1 volt potential difference applied under no-load conditions.
High KV value: The speed is faster, but the torque generated per revolution is smaller. Very suitable for smaller propellers and applications that prioritize speed.
Low KV: Slow speed but can generate significant torque. This is crucial for large propellers used in heavy lift and long endurance platforms such as 6S to 12S battery configurations.
3. Torque and thrust to weight ratio (TWR)
The torque determines the speed at which the motor changes RPM, thereby affecting its responsiveness. The thrust to weight ratio (TWR) refers to the ratio of total thrust to total takeoff weight (TOW).
Hovering: To ensure safety and control, a total distance ratio (TWR) of at least 2:1 is required.
Heavy industry operations: Ideally, a takeoff weight ratio (TWR) between 2.5:1 and 4:1 is required to cope with wind resistance and emergency maneuvers when carrying payloads.
How to choose the appropriate size of drone motor
Choosing the "appropriate" motor is a balancing task that involves the body structure, payload, and mission configuration.
1. Rack size, weight, and payload
The physical limitations of the drone body determine the maximum size of the propeller, which in turn determines the required torque of the motor. You must start from the total takeoff weight (AUW), including the batteries and the expected payload (such as cameras, spray cans, and sensors).
Rule of thumb: Heavier drones require larger propellers to efficiently generate lift. Larger propellers require lower KV motors and wider stators to provide the necessary torque without overheating.
2. Expected Applications of Drones
Agriculture and logistics: These platforms prioritize lift and flight time. They require large stator motors (e.g. over 60mm) and low KV ratings to efficiently rotate large propellers. Stability is more important than agility.
Surveying: These drones need to have endurance and low vibration characteristics. Medium sized high-efficiency motors paired with lightweight carbon fiber propellers are an ideal choice for extending battery life.
Safety and Inspection: When operating around buildings, it is usually necessary to balance endurance and agility. The medium-sized drone motor ensures that the drone maintains its position in the wind while remaining compact enough to accommodate narrow spaces.
3. Match propeller size and type
The propeller is the load; The motor is a driver.
Diameter: The larger the diameter, the higher the efficiency and lift, but if the motor torque is insufficient, the current consumption will be greater.
Pitch: The larger the pitch, the faster the speed, but the greater the power required for rotation. Industrial drones typically use propellers with lower pitch to maintain stability.
Number of propeller blades: Double bladed propellers are the most efficient in terms of endurance. Three bladed propellers fly more smoothly and are usually more suitable for video shooting to maintain stability.
