Application characteristics of permanent magnet ... - Colgate

More documents

Recommendations

Info

- PILLAY AND KRISHNAN: APPLICATION CHARACTERISTICS OF dc MOTORS FOR SERVO DRIVES 995 density of the BDCM contributes to the eddy as well as the hysteresis losses of the BDCM. A Fourier analysis of the flux density of the BDCM reveals that it can be decomposed into the following series: ~(x) = 4[sin(~)sin(x) + sin(3~)sin(3~)/3* +sin(5H)sin(5~)/5~ + sin(7H)sin(7~)/7~ + *-.]HT (14) where H is the angle between the positive zero crossing and the beginning of the peak flux density as is shown in Fig. 2. Let the fundamental component of the flux density of the BDCM be equal to that of the PMSM. The harmonics of the flux density of the BDCM therefore contribute additional core losses. The ratio of the eddy current loss in the BDCM to the PMSM is given by dividing (14) by its fundamental component, which, after some algebraic manipulation, is given by 1 + (sin (3~)/3sin(H))~ + (sin ( 5 ~ ) / sin 5 ( H))~ +(sin (7H)/7 sin (H))2 + . (15) whereas the ratio of the hysteresis loss in the BDCM to that in the PMSM is given by 1 + (sin (3~)/sin( ~ ) ) ~ + / (sin 3 ~ (5~)/sin ( ~ ) ) ~ / 5 3 + (sin (7H)/sin ( H))2/73 + . . (16) Clearly these equations depend on the value of H, which implies the electrical angle for which the flux density is constant. A graph of the core losses as a function of H is given in Fig. 13. Decreasing H, which means increasing the duration that the flux density is constant, increases both the eddy current and hysteresis losses with the increase in the eddy currents being a lot more substantial. This increased core loss of the BDeM when compared with the PMSM is an advantage of the PMSM over the BDCM. IV. CONCLUSIONS Well-known engineering selection criteria have been used to determine the application characteristics of the PMSM and the BDCM. From the results of these criteria, the following conclusions can be drawn. If the copper losses of the PMSM and the BDCM are equal, then the BDCM is capable of a 15% higher power density. The contribution of the higher harmonics to the total core losses is significant in the BDCM, and equality of the total core losses therefore demands a significantly lower loss contribution from the fundamental component of the flux density of the BDCM. These core losses increase drastically with an increase in the angle for which the flux density remains constant in the BDCM. Therefore, low core losses demand as small a constant portion of the flux density curve as permissible. The ripple torque of the BDCM is higher than that of the PMSM. The ripple torque in the PMSM is due only to the ripple in the currents. These ripple torques are of high 10' 20' 30' 40' SOo H Fig. 13. Ratio of core losses of the BDCM to PMSM. frequency and are easily damped out by the rotor. In addition to these ripples, the BDCM has a commutation ripple that depends on the speed of the machine. This makes the BDCM less suitable for high-performance position applications. Buried permanent-magnet machines are capable of a higher torque per unit current than surface-mounted machines. This is due to the contribution of the reluctance torque. With proper design, a 40% increase is possible. The BDCM has a higher torque per unit peak current than the PMSM, assuming both are operating in the constant torque mode of operation. For this reason, and because of the possibility of the higher power density of the BDCM when compared with the PMSM, the BDCM is to be preferred where weight or space is a constraint. Continuous rotor position feedback is needed by the PMSM for proper operation, whereas the BDCM requires rotor position feedback information only every 60". This is an advantage of the BDCM over the PMSM for speed servos. In a position servo, the rotor position feedback can be be used for current commutation by the PMSM, and this advantage of the BDCM over the PMSM disappears. An inverter with a given continuous current and voltage rating could theoretically drive a BDCM of 33% higher power rating than could a PMSM. However, the increased core losses of the BDCM would reduce this value. The PMSM is capable of a higher speed range than a BDCM of the same parameters. This is due to a higher restriction placed on the BDCM to the flow of current when the back emf equals the dc bus voltage. The PMSM is therefore to be preferred if flux-weakening operation is to be implemented. Buried PM machines are more sensitive to parameter changes than surface-mounted machines because of the absence of the reluctance torque term in surface-mounted machines. The surface-mounted PMSM is just as sensitive to parameter changes in the magnet flux as the BDCM. RS = 0.175 Cl L, = 2.53 mH APPENDIX I MOTOR PARAMETERS
996 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 21, NO. 5, SEPTEMBERIOCTOBER 1991 L, = 6.38 mH ha,. = 0.058 Wb 4 poles. v, = Ria + ph, + o,hd APPENDIX I1 MACHINE MODEL [I61 P. Pillay and R. Krishnan, “Modeling, analysis and simulation of a high performance, vector controlled, permanent magnet synchronous motor drive,” in Proc. IEEE IAS Ann. Mtg., 1987. [17] T. M. Jahns, G. B. Kliman, and T. W. Neumann, “Interior permanent magnet synchronous motors for adjustable-speed drives,” in Proc. IEEE IAS Ann. Mtg., 1985, p. 814-823. [18] R. Krishnan and F. C. Doran, “Study of parameter sensitivity in high performance inverter fed induction motor drive systems,’’ in Proc. IEEE IAS Ann. Mtg., 1984, pp. 510-524. I191 R. Krishnan and P. Pillay, “Parameter sensitivity in vector controlled ac motor drives,” in Proc. 1987 IEEE IECON. REFERENCES R. Krishnan, “Selection criteria for servo motor drives,” in Proc. IEEE IAS Ann. Mtg., 1986, pp. 301-308. R. Krishnan and A. J. Beutler, “Performance and design of an axial field permanent magnet synchronous motor servo drive,” in Proc. IEEE IAS Ann. Mtg., 1985, pp. 634-640. T. M. Jahns, “Torque production in permanent magnet motor drives with rectangular current excitation,” IEEE Trans. Industry Applications, vol. IA-20, no. 4, pp. 803-813, July/Aug. 1984. A. Weschta, “Design considerations and performance of brushless permanent magnet servo motors,’’ in Proc IEEE IAS Ann. Mtg., 1983, pp. 469-475. G. Pfaff, A. Weschta, and A. Wick, “Design and experimental results of a brushless ac servo-drive,” in Proc. IEEE IAS Ann. Mtg., 1982, p. 692-697. J. Mazurkiewicz, “Analysis of new compact brushless vs. pancake motors,’’ in Proc. Motorcon Conf., 1983, pp. 521-531. D. Pauly, G. Pfaff, and A. Weschta, “Brushless servo drives with permanent magnet motors or squirrel cage induction motors-A comparison,” in Proc. IEEE IAS Ann. Mtg., 1984, pp. 503-509. P. Zimmerman, “Electronically commutated dc feed drives,” Proc. Motorcon Conf., 1982, pp. 69-86. M. Brown and D. Moore, “Brushless dc or inverter motor drives: A comparison of attributes,” in Proc. Motorcon Conf., 1982, pp. 111- 123. E. K. Persson, “Brushless dc motors-A review of the state of the art,” in Proc. Motorcon Conf., 1981, pp. 1-16. S. Meshkat and E. K. Persson, “Optimum current vector control of a brushless servo amplifier using microprocessors,” in Proc. IEEE IAS Ann. Mtg., 1984, pp. 451-457. J. A. Wagner, “Numerical analysis of cogging torque in a brushless dc motor,’’ in Proc. IEEE IAS Ann. Mtg., 1975, pp. 669-674. H. Le-Huy, R. Perret, and R. Feuillet, “Minimization of torque ripple in brushless dc motor drives,” in Proc. IEEE IAS Ann. Mtg., 1985, pp. 790-797. T. M. Jahns, “Flux weakening regime operation of an interior permanent magnet synchronous motor drive, ” in Proc. IEEE IAS Ann. Mtg., 1986, pp. 814-823. T. Sebastian and G. R. Slemon, “Operating limits of inverter-driven permanent magnet motor drives,” in Proc. IEEE IAS Ann. Mtg., 1987, p. 800-805. Pragasen Pillay (S’W-M’87) received the Bachelor’s, Masters, and Ph.D degrees, all in electrical engineering. The Ph.D was obtained in 1987 at the Virginia Polytechnic Institute and State University, Blacksburg, funded by a Fulbright scholarship. He then joined the University of Newcastle upon Tyne, England. Since August 1990, he has been at the University of New Orleans, Department of Electrical Engineering, Lakefront, LA. Dr. Pillay is a member of the Industry Applications. Power Eneineerinp. and Industrial Electronics Societies of the IEEE. He serves on the Kdustrial Drives, Electric Machines and Education Committees of the IAS. He is a member of the IEE, England, a Chartered Electrical Engineer, and is a member of the Greek Honor Society, Phi-Kappa-Phi. He is a past recipient of an IEEE prize paper award. He organized a tutorial course on permanent magnet motor drives at the 1989 IAS Annual Meeting; a revised version will be presented at the 1991 IAS Annual Meeting. His research interests are in modeling, control, and design of electric machines and electric motor drive systems. Ramu Krishnan (S’81-M’82) received the B.E., M.E., and Ph.D. degrees in electrical engineering. He taught for seven years in India. He was Staff Engineer and Principal Investigator of ac servo drive projects at Gould Research Center, Rolling Meadows, IL, between 1982 and 1985. Since September 1985, he has been an Associate Professor in the Electrical Engineering Department at Virginia Polytechnic Institute and State University, Blacksburg. His teaching and research interests are in high-performance vector-controlled variable-speed drives, switched-reluctance motor drives, electrical machine design, and static power conversion. He has published more than 50 papers on these topics. He has developed a graduate program in electric motor drives and machine design at Virginia Polytechnic. Dr. Krishnan is a recipient of four IEEE-IAS awards for his papers, both presented and published. He has been Associate Editor of the IEEE TRANS- ACTIONS ON INDUSTRIAL ELECTRONICS since June 1987. He is a member of the IAS Machine Tools, Robotics, and Factory Automation Committees.
Page 1 and 2: 986 IEEE TRANSACTIONS ON INDUSTRY A
Page 3 and 4: ~ 988 IEEE TRANSACTIONS ON INDUSTRY
Page 5 and 6: 990 IEEE TRANSACTIONS ON INDUSTRY A
Page 7 and 8: 992 IEEE TRANSACTIOb IS ON INDUSTRY
Page 9: 994 IEEE TRANSACTIONS ON INDUSTRY A

Application characteristics of permanent magnet ... - Colgate

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?