Motors for Drone Applications

Unmanned Aerial Vehicles (UAVs) or drones, as they are generally known, are becoming more common. This technology is adding value in many markets including aerospace and defense, agriculture, surveillance and even e-commerce.

Drone design is a very good example of how advancements in motion solutions are helping engineers to improve our society. ‘Thrust’ is a type of force necessary to lift and maneuver flying vehicles, to achieve this, drones rely on powerful motors connected to its propellers. Below are some of the unique features for drone motors which differentiates them from motors used in other applications:

• • • High Torque 
      • Outer rotor topology can deliver higher torques compared to inner rotor technologies.  
      • The high toque requirement in drone applications is also met by electromagnetic design with high pole number (generally greater than 8). Outer rotor topology also complements this design as it provides more space for higher number of poles.
      • To produce higher torque density, strong rare earth permanent magnets are used.
      • Arc shaped magnets are typically used (instead of rectangle magnets) to achieve uniform airgap and enhance the electromagnetic performance of the motors.
      • Slotted BLDC outer rotor motors with three phase connections are preferred.
      • Windings in the drone motors are generally connected in a ‘delta’ configuration to achieve higher torque.
    • Compact and Lightweight Envelope
      • Flat motors (with small L/D ratio) provide exceptional power density.
      • Aviation grade aluminum is used in stator & rotor components to reduce weight.
      • Weight reduction features like banana cut & slots are preferred.
    • Efficiency
      • Less current consumption gives better battery life and higher flight durations.
      • Very thin laminations (generally 0.2 mm thick) are preferred to reduce core losses.
      • Due to high pole count the electrical frequency is quite high (even though motors in drones do not operate at very high speed.) which may result in high eddy current losses in stator core.
      • For better thermal performance of the motors, high temperature grade copper wires & magnets are used. Features like slots & windows on motor periphery are provided for ventilation & heat dissipation.
    • Low Noise and Vibration
      
      • Precision bearings are preferred. Because the motor relies on outer rotor design, there is a need of rotor balancing to minimize noise and vibration. Pole slot combination and uniform air gap is critical for low cogging torque and vibration.
    • Reliability
      • Drones are exposed to critical environments. To minimize failure points, sensor-less operation is preferred.

With proven experience developing power dense, highly efficient and reliable motors, gearboxes and accessories, Portescap is an exceptional partner to support drone applications. Speak with an engineer today about how we can help you select the optimal motion solution.  Contact Us today.