Effect of the number of poles on the acoustic noise from BLDC motors

Abstract

The goal of this study is to examine the effect of the number of poles on the noise from BLDC motors. To this end, the number of slots was fixed to six and the number of the poles was set to four or eight before noise was measured. Motors having different numbers of poles showed clear differences in noise; cogging torque, torque ripple and normal local force were interpreted, analyzed and compared to determine the reason for the differences. To conduct precise comparisons of noise, efforts were made to prevent changes in other variables when constructing the four-pole and eight-pole motors. Noise measurements were conducted after going through the above preparation. The results show that the eight-pole motor produced a lower noise level than the four-pole motor. To determine the cause of the noise, the cogging torque, torque ripple and radial local force were calculated, which are representative noise sources in BLDC motors, and FFT was performed to analyze their frequency components (harmonics). The calculations were made using a finite element method with the Maxwell stress tensor.

Acoustic Shielding and Scattering Effects of a Propeller Mounted Above a Flat Plate

“…The two-bladed carbon fibre propeller has a diameter, D, and a fixed pitch of 0.2286 m. The propeller was driven by a 40 A T-Motor Antigravity MN4006 brushless DC motor. The motor had 24 poles and was selected to drive the propeller to avoid any structural resonance and to reduce the noise characteristics of the motor as much as possible [17]. Control of the motor and propeller was achieved by adjusting the throttle of an electronic speed controller (ESC) to change the rotational rate, Ω.…”

Aeroacoustic Interactions of a Trailing Edge Mounted Propeller and Flat Plate

“…In the current study, noise scattering and shielding characteristics were investigated between a propeller and two flat plates of varying size. A 40 A T-Motor Antigravity MN4006 brushless DC motor was used to drive a two-bladed propeller with a fixed pitch and diameter, 𝐷, of 0.2286 m. The motor was selected for its 24 poles which reduced its overall noise contributions in the system as well as avoiding potential structural resonances [30]. The propeller was controlled through throttle adjustments in an electronic speed controller (ESC) to change the rotational rate, Ω.…”

Aeroacoustic and Aerodynamic Characteristics of Propeller Tip Geometries

“…The propeller was driven by a 40 A brushless DC motor which was controlled using an electronic speed controller (ESC). The motor in the test rig consists of 24 poles; adopted to reduce the motor noise characteristics as well as any structural resonances [26]. The rotational rate of the propeller, Ω, could be adjusted by varying its throttle setting.…”