Internal rotor motors and external rotor motors are two common structural forms in motor design. Due to the different positions of the rotors in the motor, their force characteristics and torque output forms also differ, resulting in different characteristics in torque output characteristics, dynamic response, and system integration, and making them suitable for different application scenarios.
Structural characteristics of internal rotor and external rotor motors
An internal rotor motor is a structure in which the rotor is located inside the motor and the stator is fixed on the outside. Its torque is output from the central shaft, and the stator is in a fixed state. The rotor is concentrated at the center of the motor, which gives internal rotor motors a smaller moment of inertia, resulting in good dynamic response under acceleration, deceleration, and frequent start-stop conditions.
External rotor motors employ a different structural layout, with the rotor rotating around the stator in the form of a housing. Due to their relatively larger torque radius, under the same electromagnetic conditions, this type of motor is more likely to provide higher output torque at lower speeds, and is therefore commonly used in low-speed direct-drive applications or applications requiring high starting torque.
Performance Comparison: Internal Rotor Motor vs. External Rotor Motor
1. Dimensional characteristics and shape differences
- In terms of dimensions, internal rotor motors typically have a smaller outer diameter, making them easier to design compactly and suitable for equipment with high installation space requirements.
- The overall outer diameter of the external rotor motor is relatively large, but the axial dimension is controllable, making it suitable for structural designs that can achieve high torque output within a limited axial space.
2. Heat dissipation characteristics
- Since the stator windings are usually close to the casing, the heat generated by the internal rotor motor can be easily conducted outward through the casing, which is more conducive to heat dissipation when structural conditions permit.
- The windings of an external rotor motor are located inside, and its heat dissipation effect depends more on the speed level, structural form and auxiliary heat dissipation scheme, which needs to be considered under continuous operation or high load conditions.
3. Typical Application Scenarios
- Due to its speed capability and dynamic response advantages, internal rotor motors are often used in applications with high requirements for speed and response performance, such as power tools, automation equipment, precision instruments, small pumps, and some drone drive systems.
- External rotor motors are widely used in low-speed, high-torque, or continuous operation scenarios such as fans, blowers, electric vehicle wheel hubs, home appliance drives, and electric sunshade systems.
The choice between internal rotor and external rotor motors depends on specific application requirements. Appropriately selecting the motor type based on equipment load, installation space, and operating environment can effectively improve system performance and reliability.
Kinmore Motor offers a variety of brushless DC motor solutions, including internal rotor, external rotor, and coreless motors, which can be customized in terms of speed, torque, and power parameters to meet different application needs, while also supporting optimized structural layout and heat dissipation design. Through flexible motor solution matching, users can achieve higher performance and operational stability in various home appliances, industrial automation, and mobile devices.
