The advantage of skewed stator slots in an electric machine's stator assembly are primarily related to improving the machine's performance and reducing unwanted effects that can arise from having straight or parallel slots. Here are some key advantages:
1. Reduced Cogging Torque
Skewing the slots reduces the magnetic attraction between the rotor and stator teeth, which lessens the cogging torque. Cogging torque refers to the pulsating torque that occurs when the motor rotates through a series of magnetic poles without load, causing a jerky motion. By skewing the slots, the alignment of the teeth with the rotor magnets changes gradually, thus smoothing out torque variations.
2. Lower Noise and Vibration
The reduction in cogging torque also results in lower noise and vibration levels during operation. This is particularly important for applications requiring smooth and quiet operation, such as precision machinery and household appliances.
3. Improved Commutation
In brushless DC (BLDC) motors or permanent magnet synchronous motors (PMSMs), skewed slots help improve commutation by reducing torque ripple due to uneven back EMF waveforms across the phases. This leads to a more consistent output torque and better overall efficiency.
4. Enhanced Power Factor
Skewed slots can contribute to enhancing the power factor by making the phase currents more sinusoidal, which improves the power quality and reduces harmonic content in the current waveform.
5. Better Thermal Performance
Since the magnetic field distribution is more uniform with skewed slots, it can lead to a more even distribution of heat, potentially increasing the motor’s thermal performance and prolonging its lifespan.
5. Summary
skewing the stator slots is a design strategy used to optimize motor performance, reduce undesirable mechanical effects, and enhance the overall operating characteristics of the electric machine. It is especially beneficial for high-performance and low-noise applications where smooth operation and high efficiency are crucial.