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What is the difference between an internal rotor motor and an external rotor motor?

Release time:2024/02/22

What is the difference between an internal rotor motor and an external rotor motor?


Permanent magnet synchronous motors can be divided into outer rotor structure and inner rotor structure according to the position of the rotor in the motor. The difference is whether it rotates inside or outside. The inner rotor structure is an inner rotor structure, and the outer rotor structure is an outer rotor structure. Usually the rotating part is the part embedded with magnetic steel, which is the rotor; the non-rotating part is the coil part, which is the stator. The characteristic of the outer rotor motor is that the stator is fixed in the middle of the shaft, and the rotor rotates on the periphery of the stator. It also has a radial air gap flux structure. Compared with the inner rotor structure, the rotor and stator have changed positions. The stator is in a different position. The inside of the motor is called the inner stator, and the rotor on the outside of the motor is called the outer rotor.


In practical applications, the inner rotor and outer rotor have the following differences:

1. Difference in rotation position. 

The inner rotor, that is, the transmission part of the motor is inside, the casing is static, and the inside rotates; the outer rotor is internally static, and the outer casing rotates. Generally speaking, the embedded magnet steel (permanent magnet) part will rotate, but the coil part does not rotate. According to the permanent magnet inlay process and position, the outer rotor and the inner rotor can also be distinguished.


2. The size of the permanent magnet. 

The permanent magnet of the outer rotor is small in size and axial size, and the system operation stability is good. The inner rotor permanent magnet has a large volume, correspondingly larger axial size, high center of gravity, and poor operating stability.


3. Speed. 

Taking the same brushless DC motor as an example, the speed of the inner rotor motor is significantly higher than that of the outer rotor motor.


4. Application. 

The inner rotor is often used in power machinery such as motors, generators, gas turbines, and compressors, while the outer rotor is usually installed inside the impeller to take on the role of heat dissipation and cooling.


The advantages and disadvantages of the inner rotor and the outer rotor are:


The advantages of the inner rotor include lightweight fan blades, easy production and assembly of the motor, and lower cost. However, there are problems such as rapid heating of the motor, high power consumption, unstable voltage, easy damage to the motor, and short life.


The advantage of the outer rotor is that it can be made into a fully enclosed structure and can run quickly after startup. It has low power consumption, high speed, high efficiency, and long service life. However, it has poor sealing, large rotor inertia, high noise, and high requirements for dynamic balance.


External rotor motor structure

The stator core of the external rotor motor set is made of silicon steel sheets with good magnetic conductivity. There are many slots on the outer periphery of the stator core, and the generator windings are embedded in the slots. The stator core is installed on the stator bracket. One end of the stator bracket has a flange installed on the nacelle base, and the other end is the outer rotor shaft. The outer rotor is installed on the main shaft of the motor to form an outer rotor motor.


Ningbo Nide Mechanical Equipment Co., Ltd. is committing to provide customers with highly automated, intelligent, and flexible motor manufacturing production solutions, and focusing on the production line of stator, rotor and final assembly of various motors.

Our machines are mainly applied to induction motors, BLDC motor, universal motor, three phase motor, single phase motor, AC motor, DC motor, such as wheel hub motor, hair-pin motor, drone motor, FPV UAV motor, washing machine motor , air conditioner motor, pump motor, cooler motor, alternator motor, fan motor, ceiling fan motor, compressor motor, power tool motor, vacuum cleaner motor, mixer motor, series motor, electrical car motor, electric toothbrush motor, hair dryer motor, electric shaver motor,etc.


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