Is there a difference between an external rotor motor and an internal rotor motor?

The rotor is one of the very important parts of the DC motorand BLDC motor. The outer rotor and the inner rotor are two common rotor types in the field of motors. According to the position of the rotor, DC motors can be divided into inner rotor motors and outer rotor motors. In an external rotor motor, the rotor is located on the outside (outside the motor) and the stator is located inside the motor. In contrast, in an internal-rotor motor, the rotor is located inside the motor and the stator is located outside the motor. You may want to ask: What's the difference between them?
The differences between internal rotor motors and external rotor motors are as follows:

1. Different rotation positions: the inner rotor motor rotates internally, the main shaft of the rotor motor rotates together, the motor base is fixed, the outer shell is used as the stator, and the inner rotor and the main shaft are used as the rotor. The external rotor motor rotates externally; the external rotor motor has the rotor rotating together with the motor casing, the motor main shaft is fixed, the casing serves as the rotor, and the interior and the main shaft serve as the stator.

2. Different speeds: In brushless DC motors, the speed of the inner rotor motor is significantly higher than that of the outer rotor motor. The inner rotor generally has fewer poles, higher rotational speed, and smaller torque; the outer rotor generally has more poles, lower rotational speed, and larger torque.

3. The rotational inertia of the outer rotor motor is greater than the rotational inertia of the inner rotor: when the rotor weight is the same, the kv of the inner-rotating motor is high and the torque is low; the inertia of the outer-rotating motor is large, thus improving the performance of the motor under unstable loads. efficiency and output power.

4. Different application areas: Inner rotors are often used in power machinery such as generators, gas turbines, compressors, etc., while outer rotor motors can be used in different situations according to their characteristics, such as low speed and large torque, direct drive, constant speed, and requirements. Situations where the speed changes are small.

In general, the outer rotor has higher mechanical strength than the inner rotor and is suitable for high-speed, low-torque working conditions, while the inner rotor is suitable for medium-speed and medium-high torque working conditions. Both rotors have their own advantages and disadvantages, and the specific application needs to be selected according to the actual situation.

Article source: https://article-realm.com/article/Writing-Speaking/53459-Is-there-a-difference-between-an-external-rotor-motor-and-an-internal-rotor-motor.html