Sources of torque ripple
Motor torque is the magnitude of the force exerted by the motor's rotation. Torque ripples not only cause vibrations in the motor itself, but also in components that are directly or indirectly in contact with the motor. The main sources of torque ripples include: torque current fluctuations, cogging torque, and manufacturing processes.
The dangers of torque ripple
loud noise
The degree of harm caused by noise depends primarily on its frequency, intensity, and duration of exposure. Noise not only interferes with people's lives and work but also damages hearing and can even induce various carcinogenic and fatal diseases.
Electric motors are used in many everyday products, such as fans, air conditioners, and ceiling fans. Loud fan noise and loud air conditioner noise can directly affect sleep quality.
It can easily cause system resonance.
In the early 19th century, a troop of Napoleonic soldiers, under the command of their commander, marched with imposing, perfectly synchronized steps across a bridge in Angers, France. Near the middle of the bridge, it suddenly began to vibrate violently and eventually collapsed, causing many soldiers and civilians to fall into the water and drown. Subsequent investigations revealed that the culprit behind this tragedy was resonance! The frequency generated by the soldiers marching in unison matched the bridge's natural frequency, amplifying its vibrations. When the amplitude reached its maximum, exceeding the bridge's structural strength, it collapsed.
Periodic torque fluctuations, if the frequency of the fluctuations coincides with the system's natural frequency, will cause resonance. This is especially true for products with plastic casings, where torque fluctuations are very prone to causing resonance, such as fan resonance and air conditioner resonance.
High electromagnetic interference, failed EMI certification
One of the sources of torque fluctuation is current fluctuation. The changing current generates a changing magnetic field. Large current fluctuations lead to large radiation, which in turn causes conduction and spatial radiation to exceed the standard.
Poor machining accuracy: Torque fluctuations lead to uneven machining, and may even cause breakage or damage to machined parts.
Accelerated system aging: Torque fluctuations cause periodic wear on one side of mechanical components.
Improvement of torque ripple
Improvements to the motor body: The back EMF waveform is designed to be sinusoidal, the motor has a skewed slot design, and the cogging torque is minimized.
By employing FOC technology, the torque is kept stable at all times, with high control precision and sinusoidal current variation, minimizing torque and current fluctuations.
Square wave current waveform
FOC current waveform
