Difference between inner rotor brushless motor and outer rotor brushless motor

Inner rotor and outer rotor brushless motors are two common configurations of brushless motors, each with its own set of characteristics and applications. Here's a comparison of the two:

1. Rotor Placement:

• Inner Rotor Brushless Motor:

  • In an inner rotor brushless motor, the rotor (the part that rotates) is located inside the stator (the stationary part).
  • This means that the rotor is closer to the motor's central axis.

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• Outer Rotor Brushless Motor:

  • In an outer rotor brushless motor, the rotor is located on the outside of the stator.
  • This results in the rotor being positioned farther away from the motor's central axis.

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2. Size and Form Factor:

• Inner Rotor Brushless Motor:

  • Inner rotor motors are typically more compact and have a smaller diameter.
  • They are well-suited for applications where space is limited.

• Outer Rotor Brushless Motor:

  • Outer rotor motors tend to have a larger diameter and a more flattened, pancake-like shape.
  • They can provide higher torque output due to their larger size.

3. Inertia and Response:

• Inner Rotor Brushless Motor:

  • Inner rotor motors generally have lower inertia due to their smaller rotor size.
  • They tend to respond quickly to changes in input signals and are often used in applications requiring rapid acceleration and deceleration.

• Outer Rotor Brushless Motor:

  • Outer rotor motors have higher inertia because of their larger rotor size.
  • They are better suited for applications that require higher torque and smoother, continuous operation.

4. Cooling:

• Inner Rotor Brushless Motor:

  • Cooling inner rotor motors can be more challenging because of their compact size.
  • They may require additional cooling mechanisms in high-power applications.

• Outer Rotor Brushless Motor:

  • Outer rotor motors often have more surface area exposed for cooling.
  • This can make them more suitable for high-power applications where effective cooling is essential.

5. Applications:

• Inner Rotor Brushless Motor:

  • Commonly used in applications where rapid changes in speed and direction are required, such as drones, quadcopters, and some types of fans.
  • Also suitable for compact devices with limited space.

• Outer Rotor Brushless Motor:

  • Found in applications requiring high torque output and continuous operation, such as industrial machinery, electric bicycles, and some types of electric vehicles.

In summary, the choice between an inner rotor and an outer rotor brushless motor depends on the specific requirements of the application. Inner rotor motors are favored for their compact size and rapid response, while outer rotor motors excel in providing high torque and continuous operation. Selecting the appropriate motor type is crucial to achieving optimal performance in a given application.