Article

# The effect of magnet geometry on electric motor vibration

California Univ., Berkeley, CA

IEEE Transactions on Magnetics (Impact Factor: 1.42). 12/1991; DOI: 10.1109/20.278787 Source: IEEE Xplore

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**ABSTRACT:**With the advent of the mobile phone, Digital Multimedia Broadcasting (DMB) service for multimedia data communication will soon be realized. With regard to the acoustic aspects of this service, a smaller and lighter microspeaker also soon will be implemented in MP3 song players and speakerphones. The sound quality of such microspeakers, as evaluated with reference to total harmonic distortion (THD) is becoming more important. THD is the proportion of the higher-order frequency output response to a sinusoidal input signal. It is affected by uneven magnetic distribution and nonlinear responses of diaphragms. In this work, THD was analyzed in consideration of the coupling effects between mechanical vibration and electromagnetic exciting forces. Simulated THD results were compared with the experimental data. The THD in the lower frequency range increased due to the increased displacement of the voice coil and the elevated high-order component response of the sound pressure. KeywordsCoupling effect-Microspeaker-Speedance-Sound pressure level (SPL)-Total harmonic distortion (THD)Journal of Mechanical Science and Technology 01/2008; 24(9):1763-1769. · 1.09 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**The use of neodymium and other rare earth magnets in brushless DC motors increases their torque, but also magnetically induced vibration due to rotating stator tooth force. This paper investigates the influence of the stator coil winding pattern on stator tooth force and torque from three common winding patterns, e.g., center-tapped-wye (CTY), wye (Y) and delta (Δ), with equivalent torque output. Stator tooth forces and torque in a 6-pole, 9-tooth, 3-phase motor were calculated from the flux density using finite element analysis and the Maxwell stress tensor. Their frequency spectra were analyzed through multi-dimensional spectral analysis. The analyses show that the driving frequencies of tooth forces appear at the integer multiple of rotor speed multiplied by the number of pole. The driving frequencies of forces have larger amplitudes at the leading edge than at the trailing edge of the tooth. At low frequencies, CTY and Δ windings produce larger amplitudes at the leading edge and smaller amplitudes at the trailing edge than those of Y winding. Y windings may produce higher torque ripple than the other winding patternsIEEE Transactions on Magnetics 12/1994; · 1.42 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**As permanent-magnet motors and generators produce torque, vibration occurs through the small air gap due to the alternating magnetic forces created by the rotating permanent magnets and the current switching of the coils. The magnetic force can be calculated from the flux density by finite element methods and the Maxwell stress tensor in cylindrical coordinates. The transition of the magnetic force with the rotation of rotor and the commutation of current, was analyzed by assuming the quasi static magnetic field. The cogging and the commutating torques were also investigated by integrating the magnetic shear force in a small air-gap. In addition, the characteristics of these forces and torques were also investigated by multi-dimensional spectral analysis, so that this paper makes it possible to predict the frequency spectrum of magnetic force and the torque in a brushless do motor.Journal of Mechanical Science and Technology 02/1996; 10(1):37-48. · 1.09 Impact Factor

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