Home » FAQ » Why BLDC motors are noiseless?

Why BLDC motors are noiseless?

Harmonics in the electromagnetic torque, known as torque ripple or pulsating torque, exist in all electrical machines regardless of type or design. The harmonics are created by non-idealities in the electromagnetic fields produced by the rotor and stator interaction. Specifically, all permanent magnet (PM) based machines, irrespective of type, produce torque ripple that can be significant and create undesirable noise and vibration. . Ironically, the same reason that makes PM based machines ideal for many EV/HEV applications (their relatively high power density), makes them naturally prone to relatively undesirable high torque ripple. The interaction between the PMs MMF and the varying airgap permeance due to slots creates cogging toque (also known as no current torque), a torque ripple components that is unique to PM based machines. The tendency of the PMs on the rotor to align with stator slots (even when the no stator excitation is provided), does not provide any additional average torque, but can results in high torque ripple.

So for this case I would make the following generalization: For low-speed, high-torque applications, I can see how a traditional PMSM/BLDC would have a relatively large torque ripple due to the large cogging torque created by the relatively small airgap and strong PMs used. However, once operating at high-speed, (as Art mentioned) I don't see many overall advantages that make BLDCs/PMSMs have over more or less inherent torque ripple than IM, and vise-verse. I think that at that point, it is really machine and application dependent question.

Post a Comment:

Plz Calculate (3 - 1) =
(Your comment will show after approved.)

You may also like:

Featured Articles
Non-Enclosure Variable Frequency Drive ... Non-Enclosure Variable Frequency Drive (VFD)No enclosure (cover), reducing installation space and cost effective. Widely used in All-In-One control cabinet. Keep the same ...
Variable frequency drive application ... Variable frequency drive application guideVariable Frequency Drive (VFD) can be used in lots of fields. Variable frequency drives are widely used to control the speed of ...
Variable frequency drive in HVAC ... Variable frequency drive in HVAC systemsVariable frequency drives (VFD) have been used for HVAC systems in buildings for more than 40 years. But only in recent years, ...
Variable Frequency Drive Harmonics and ... A discussion of the benefits of variable frequency drives often leads to a question regarding electrical harmonic distortion ...
Three phase inverters Three phase invertersIn the variable frequency drive rectifier paper, it explains how to go from three phase alternating current voltage to a direct ...
Variable Frequency Drive Service
VFD manufacturers
Variable Frequency Drive Sales Email buy@vfds.org
Variable Frequency Drive Support Email tech@vfds.org