What are the structural differences between external rotor motors and internal rotor motors?

There are various types of electric motors, and their performance across all aspects continues to improve. Among them, inner rotor motors and outer rotor motors are commonly used types, widely applied across multiple industries. So, what are the specific differences between them in terms of structure and performance?

Structurally, the core difference lies in the relative positions and motion states of the rotor and stator:

In an internal rotor motor, the rotor rotates synchronously with the main shaft. The motor frame remains stationary, with the outer casing functioning as the stator, while the inner shaft and main shaft act as the rotor.

In an external rotor motor, the rotor rotates along with the motor casing. The motor shaft is fixed, with the casing serving as the rotor, while the inner shaft and main shaft function as the stator.

Performance-wise, each exhibits distinct characteristics:

Internal rotor motors typically feature fewer poles, delivering high speed but low torque; external rotor motors have more poles, offering low speed but high torque.

For equivalent rotor weight, the internal rotor's moment of inertia is lower than the external rotor's. Consequently, internal rotor motors exhibit higher kv values and lower torque, while external rotor motors, due to their larger moment of inertia, demonstrate superior efficiency under unstable loads.

In application scenarios and characteristics, internal rotor motors, with their low torque and high speed, are commonly used in applications like vehicle models. External rotor motors offer superior heat dissipation and often operate on DC power, providing robust power support for the normal operation of mechanical equipment, making them a key component in many devices. Additionally, the rotating parts (rotors) of both types typically have embedded magnets, while the stator remains stationary.

Regarding maintenance, repairing an internal rotor motor that has burned out is challenging because its enameled wire is difficult to rewind by hand.

Therefore, beyond understanding their differences, we must also prioritize routine maintenance.