An Accurate Automatic Phase Advance Adjustment of Brushless DC Motor IEEE TRANSACTIONS ON MAGNETICS, VOL. 45, NO. 1,p.120~126,JANUARY 2009 Chun-Lung Chiu, Yie-Tone Chen, Yu-Hsiang Shen, and Ruey-Hsun Liang Adviser : Ming-Shyan Wang Student :Yu-Ming Liao

Outline Abstract Introduction Theoretical analysis System setup Experimental results Conclusion References

Abstract For improved efficiency and torque performance, brushless DC (BLDC) motors require a phase advance circuit. Performance curves of phase advance angle versus frequency for a conventional circuit do not work well when the harmonic components are considered. We therefore propose an improved circuit in which the phase advance angle is more accurate than that of a conventional circuit when the harmonic components are considered.

Introduction(1/3) The phase advance concept has been proposed to increase the efficiency of the motor in former research works[1]–[4]. The purpose of phase advance is to let the current climb first before the corresponding back electromotive force (EMF) goes into the smooth field. As for the methods to realize the phase advance, the hardware circuit or software of single chip can be used to achieve the purpose.

Introduction(2/3) In the general application in industry, the direct phase advance method is usually used to put the Hall sensor at a leading position to obtain better performance while the rotor runs at high speed. However, it will cause a start-up problem if the Hall sensor is put too far in advance, and the Hall sensor only can be put at a fixed position.

Introduction(3/3) For the conventional phase advance circuit shown in Fig. 2, it only considers the fundamental sinusoidal component in the analysis of phase lead [2], [3]. The phase advance angle of a conventional circuit is not satisfactory, so an improved circuit is proposed in this paper.

Theoretical analysis(1/9) The difference between and phases of the induced signal of Hall sensor in Fig. 2 is , as shown in Fig. 3. Then, the induced signal of the Hall sensor can be further approximated as a standard symmetric trapezoidal wave as shown in Fig. 4.

Theoretical analysis(2/9) To obtain the exact analysis for this trapezoidal wave, the method of Fourier series is used.

Theoretical analysis(3/9)

Theoretical analysis(4/9)

Theoretical analysis(5/9) The transfer function of the conventional phase advance circuit can be derived as presented in (2).

Theoretical analysis(6/9) The phase advance angle of conventional circuit does not work well when the harmonic component response is considered.

Theoretical analysis(7/9) So an improved circuit as shown in Fig. 6 is proposed in this paper. The transfer function of this improved circuit can be proved as (3).

Theoretical analysis(8/9) After the Fourier series in Table I are substituted into (3) to calculate the solution, the phase advance angle of the proposed circuit can be obtained as shown in the curve of Fig. 7.

Theoretical analysis(9/9) The output waveform becomes undiscerning when the phase advance circuit is used; so the commutative phase point will be hard to decide. In Figs. 8 and 9, the comparators are used to generate a rectangular waveform in order to decide the more correct commutative phase point.

System setup

Experimental results(1/7) A single-phase BLDC motor with outer rotor of four poles is used for the experiments and the related Hall sensor type is HW300B.

Experimental results(2/7) Experimental waveforms of the conventional circuit

Experimental results(3/7) Experimental waveforms of the proposed circuit

Experimental results(4/7) n=120*f/P n：轉速 f：頻率 P：極數 3000(rpm)=120*100(Hz)/4 計算超前角度

Experimental results(5/7) The theoretical analysis and experimental results are compared to each other, and the problem which the phase advance angle of the conventional circuit does not work well is solved now.

Experimental results(6/7) For the same output power, the proportion of the reduced power consumption by the proposed method to the input power consumption of the conventional circuit is shown in Fig. 19. It explains the advantage with the proposed circuit. Because the phase advance angle of the conventional circuit is already over 6 deg in 1000 rpm, its efficiency is therefore the worst in this speed.

Experimental results(7/7) The current waveforms have been improved at 1000 rpm and 5000 rpm but are similarly the same at 3000 rpm. It is due to the reason that the phase angles are nearly equal at 3000 rpm for the direct phase advance and proposed circuits.

Conclusion The phase advance angle of the conventional circuit is found not to work well when the harmonic components are also considered. An improved phase advance circuit has been proposed in this paper. In 33.33 Hz–166.67 Hz, the phase advance angle of the proposed circuit can climb around to 12.38 deg , but the conventional circuit climbs only to 3.89 deg when the harmonic component analysis is conducted for both circuits. The proposed circuit still appears its attraction when compared with the results using the direct phase advance method.

References(1/2) [1] S.-I. Park, T.-S. Kim, S.-C. Ahn, and D.-S. Hyun, “An improved current control method for torque improvement of high-speed BLDC motor,” in Proc. IEEE APEC, 2003, pp. 294–299. [2] C. M. Chao, C. P. Liao, D. R. Huang, and T. F. Ying, “A new automatic phase adjustment of optical drive signal,” IEEE Trans. Magn., vol. 34, no. 2, pp. 417–419, Mar. 1998. [3] D. R. Huang, C. Y. Fan, S. J.Wang, H. P. Pan, T. F. Ying, C. M. Chao, and E. G. Lean, “A new type single-phase spindle motor for HDD and DVD,” IEEE Trans. Magn., vol. 35, pp. 839–844, Mar. 1999. [4] A. Lelkes and M. Bufe, “BLDC motor for fan application with automatically optimized commutation angle,” in IEEE Power Electronics Specialists Conf., Aug. 2004, pp. 2277–2281. [5] A. Karwath, M. Moini, and E. Wunsch, “Driver circuit for brushless DC motors,” U.S. Patent 5 583 404, Dec. 1996. [6] A. Karwath, M. Moini, and E. Wunsch, “Driver circuit for brushless DC motors,” U.S. Patent 5 717 297, Feb. 1998. [7] A. Karwath, M. Moini, and E. Wunsch, “Driver circuit for brushless DC motors,” U.S. Patent 6 384 554 B1, May 2002.

References(2/2) [8] A. Karwath, M. Moini, and E. Wunsch, “Driver circuit for brushless DC motors,” U.S. Patent 7 067 998 B2, Jun. 2006. [9] R. Carlson, M. Lajoie-Mazenc, and J. C. dos S. Fagundes, “Analysis of torque ripple due to phase commutation in brushless dc machines,” IEEE Trans. Ind. Appl., vol. 28, no. 3, pp. 632–638, May/Jun. 1992. [10] B.-H. Kang, C.-J. Kim, H.-S. Mok, and G.-H. Choe, “Analysis of torque ripple in BLDC motor with commutation time,” in IEEE Industrial Electronic Conf., Jun. 2001, vol. 2, pp. 1044–1048. [11] H. Zeroug, B. Boukais, and H. Sahraoui, “Analysis of torque ripple in a BDCM,” IEEE Trans. Magn., vol. 38, no. 1, pp. 1293–1296, Mar. 2002. [12] C.-L. Chiu, Y.-T. Chen, and W.-S. Jhang, “Properties of cogging torque, starting torque, and electrical circuits for the single-phase brushless DC motor,” IEEE Trans. Magn., vol. 44, no. 10, pp. 2317–2323, Oct. 2008. [13] J. Ni, L.Wu, B. Zhang, W. Jin, and J. Ying, “A novel adaptive commutation angle method for single phase BLDC motor,” in IEEE ICEMS Int. Conf., Oct. 2007, pp. 446–449.

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