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What are the effects of the air gap size of a motor on its performance?

Release time:

2026-01-22

The larger the air gap, the greater the magnetic resistance of the motor's magnetic circuit. In order to establish a magnetic field of the same strength, the stator winding needs to input a larger excitation current.

What are the effects of the air gap size of a motor on its performance?

The impact on excitation current and power factor
The larger the air gap, the greater the magnetic resistance of the motor's magnetic circuit. In order to establish a magnetic field of the same strength, the stator winding needs to input a larger excitation current.
Excitation current belongs to reactive current, which will reduce the power factor of the motor and increase the reactive power loss of the power grid, especially for asynchronous motors. On the contrary, the smaller the air gap, the smaller the magnetic resistance, the smaller the excitation current, and the higher the power factor.
The impact on efficiency and temperature rise
A smaller air gap can reduce magnetic circuit losses and improve the energy conversion efficiency of the motor; However, a small air gap can increase the stray losses between the stator and rotor, and lead to insufficient heat dissipation space, which can easily cause excessive temperature rise in the motor.
Although a larger air gap results in lower stray losses and slightly better heat dissipation, the increase in excitation current leads to an increase in copper loss, which offsets these advantages and ultimately reduces the overall efficiency of the motor.
The impact on operational stability and noise
Uneven air gap can cause unilateral magnetic pulling force during motor operation, leading to rotor vibration, increased noise, and in severe cases, friction between the stator and rotor (sweeping the bore).
If the air gap is too large, it will reduce the coupling strength of the magnetic field, weaken the motor's ability to resist load fluctuations, and decrease the stability of the speed; A reasonable air gap size can balance magnetic pulling force, reduce vibration and noise, and improve operational stability.
The impact on control performance
For motors such as servo motors and stepper motors that require high-precision control, the size of the air gap will affect their torque ripple characteristics.
A small air gap can easily cause torque pulsation due to magnetic saturation, reducing positioning accuracy; If the air gap is too large, it will weaken the electromagnetic torque output, resulting in slower motor response speed and decreased control sensitivity.
Requirements for Manufacturing and Assembly
The smaller the air gap, the higher the machining accuracy (such as roundness and coaxiality) and assembly process requirements for the motor stator and rotor, which will increase production and manufacturing costs; When the air gap is large, the difficulty of processing and assembly is reduced, the fault tolerance is stronger, and it is more suitable for large-scale production.

Keyword:

The core function of a reducer

Key points for selecting motors

On this Thanksgiving Day, we are truly grateful for the mysterious and wonderful dinner organized by our headquarters. It has been a perfect opportunity to unwind and release the year's accumulated pressures. We sincerely thank our company for providing such an excellent platform, allowing us to serve friends and clients from around the world.

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The core function of a reducer

The rated speed of the motor is often higher than the actual required speed of the equipment, and the reducer can accurately adjust the speed to ensure that the actuator (such as conveyor belt, robotic arm) operates at the optimal working speed.