What is meant by "skewing" and how does it affect AC motor performance?
1 Answer
"Skewing" in the context of AC motors refers to intentionally offsetting or tilting the stator slots or rotor bars of an electric motor to mitigate the effects of cogging, improve motor performance, and reduce noise and vibration. Cogging is the phenomenon where an electric motor experiences resistance or "cogs" as it starts to rotate due to the interaction between the magnetic fields of the stator and rotor. This can lead to jerky motion, increased energy consumption, and mechanical stress on the motor.
Skewing is often employed in squirrel cage induction motors and other types of AC motors to achieve several benefits:
Reduced Cogging: Skewing the stator slots or rotor bars breaks up the uniformity of the magnetic field distribution, reducing the likelihood of the rotor getting "stuck" in certain positions during startup. This results in smoother rotation and eliminates or minimizes cogging.
Improved Starting Performance: Cogging can hinder the starting torque of the motor. By reducing or eliminating cogging through skewing, the motor's starting performance is improved, and it can accelerate more smoothly.
Vibration and Noise Reduction: Cogging can cause mechanical vibrations and audible noise during motor operation. Skewing helps in reducing these vibrations and noise by preventing abrupt changes in magnetic attraction between the stator and rotor.
Enhanced Efficiency: A smoother startup and operation due to skewing can lead to improved energy efficiency as the motor doesn't need to overcome the resistance caused by cogging.
Extended Motor Life: The reduction of mechanical stresses caused by cogging can contribute to a longer lifespan for the motor by minimizing wear and tear.
Skewing can be implemented in various ways, such as by slightly angling the stator or rotor slots or by offsetting the rotor bars. The specific angle and skewing technique depend on factors like motor design, intended application, and the severity of cogging. However, excessive skewing can lead to negative effects, such as increased losses due to eddy currents or mechanical imbalances, so it's important to strike a balance between reducing cogging and maintaining motor efficiency.
In summary, skewing is a technique used to improve the performance and efficiency of AC motors, particularly in applications where smooth operation, reduced cogging, and minimal noise and vibration are crucial.
Skewing is often employed in squirrel cage induction motors and other types of AC motors to achieve several benefits:
Reduced Cogging: Skewing the stator slots or rotor bars breaks up the uniformity of the magnetic field distribution, reducing the likelihood of the rotor getting "stuck" in certain positions during startup. This results in smoother rotation and eliminates or minimizes cogging.
Improved Starting Performance: Cogging can hinder the starting torque of the motor. By reducing or eliminating cogging through skewing, the motor's starting performance is improved, and it can accelerate more smoothly.
Vibration and Noise Reduction: Cogging can cause mechanical vibrations and audible noise during motor operation. Skewing helps in reducing these vibrations and noise by preventing abrupt changes in magnetic attraction between the stator and rotor.
Enhanced Efficiency: A smoother startup and operation due to skewing can lead to improved energy efficiency as the motor doesn't need to overcome the resistance caused by cogging.
Extended Motor Life: The reduction of mechanical stresses caused by cogging can contribute to a longer lifespan for the motor by minimizing wear and tear.
Skewing can be implemented in various ways, such as by slightly angling the stator or rotor slots or by offsetting the rotor bars. The specific angle and skewing technique depend on factors like motor design, intended application, and the severity of cogging. However, excessive skewing can lead to negative effects, such as increased losses due to eddy currents or mechanical imbalances, so it's important to strike a balance between reducing cogging and maintaining motor efficiency.
In summary, skewing is a technique used to improve the performance and efficiency of AC motors, particularly in applications where smooth operation, reduced cogging, and minimal noise and vibration are crucial.