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International Journal of Rotating Machinery
Volume 2006 (2006), Article ID 63214, 7 pages

Noise Source Identification of Small Fan-BLDC Motor System for Refrigerators

1CRC for Integrated Engineering Asset Management, School of Engineering Systems, Queensland University of Technology, 2 George Street, Brisbane, QLD 4001, Australia
2School of Mechanical Engineering, Pukyong National University, Yondang-dong Nam-gu, Busan 608-739, South Korea
3Digital Appliance Research Laboratory, LG Electronics Inc., Kuro 3 dong, Kuro-gu, Seoul, South Korea

Received 1 June 2006; Revised 4 September 2006; Accepted 6 September 2006

Copyright © 2006 Yong-Han Kim et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Noise levels in household appliances are increasingly attracting attention from manufacturers and customers. Legislation is becoming more severe on acceptable noise levels and low noise is a major marketing point for many products. The latest trend in the refrigerator manufacturing industry is to use brushless DC (BLDC) motors instead of induction motors in order to reduce energy consumption and noise radiation. However, cogging torque from BLDC motor is an undesirable effect that prevents the smooth rotation of the rotor and results in noise. This paper presents a practical approach for identifying the source of excessive noise in the small fan-motor system for household refrigerators. The source is presumed to a mechanical resonance excited by torque ripple of the BLDC motor. By using finite element analysis, natural frequencies and mode shapes of the rotating part of the system are obtained and they are compared with experimental mode shapes obtained by electronic torsional excitation test which uses BLDC motor itself as an exciter. Two experimental validations are carried out to confirm the reduction of excessive noise.