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A Novel Rotor Configuration and Experimental Verification of Interior PM

Synchronous Motor for High-Speed ApplicationsIEEE TRANSACTIONS ON MAGNETICS, VOL. 48, NO. 2, FEBRUARY 2012

By Sung-Il Kim, Young-Kyoun Kim, Geun-Ho Lee,and Jung-Pyo Hong

Outline Abstract

Introduction

Rotor Design Of High-Speed IPMSM Initial Rotor Shape

Initial Rotor Shape

Experimental Design

Rotor-Shape Optimization

Test Results And Discussion

Conclusion

References

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Abstract

On account of high efficiency and high power density, permanent-magnet

synchronous motors (PMSMs) are mainly applied to a high-speed

machine. Especially, because of relatively easy magnetic circuit design and

control. However, the surface-mounted PMSM has some weak points due

to a sleeve, which is nonmagnetic steel used in order to maintain the

mechanical integrity of a rotor assembly in high-speed rotation. 112/04/19 3

Introduction

The IPMSM does not essentially need the sleeve, because permanent magnet is inserted inside the rotor. Moreover, the IPMSM has higher power density than the surface-mounted PMSM, because it can use a magnetic and a reluctance torque with proper current vector control.

Thus, the two-pole IPMSM considering electrical and mechanical characteristics is designed and fabricated as the driving motor of a 8-kW, 40000 r/min class air blower. In the end, the superiority and reliability of the IPMSM in high-speed operation is verified by the results obtained by test.

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Rotor Design Of High-Speed IPMSM

Fig. 2 displays the manufactured stator with three-phase coils, and it is applied to the surface-mounted PMSM and IPMSM. Also, the main design specifications given in Table I are qually applied for them.

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Fig. 2 Manufactured stator with three-phase coils. (a) Top view. (b) Side view.

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Initial Rotor Shape

Fig. 3 shows a variety of rotor configurations of the IPMSM with two poles. The diameter of the rotor and shaft is the same.

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Partial rotor configurations according to design factor variation. (a) Accordingto the number of magnet layers. (b) According to the number of bridgesin the second layer. c) According to pole angle.

Experimental Design

In this paper, the analysis of variance (ANOVA) , one of the statistical analysis methods, is utilized to identify the design factors that have the greatest influence on the characteristics of the IPMSM.

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FEA results

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As the pole angle grows, the average torque and back-electromotive force (emf) also increased, but the saliency and maximum stress are reduced.

Average torque is more affected by back-emf than by saliency.

When the number of bridges is three in the second layer of the permanent magnet, the average torque and back-emf are largest.

As the number of magnet layers increases, saliency is generally increased, but the average torque and back-emf tend to decrease.

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Rotor-Shape Optimization

The aim of the rotor optimization is to secure electrical performance and mechanical strength. In addition, the amount of PM should be minimized. Accordingly, as shown in Fig, the design parameters based on the results of the experimental design are chosen for the optimization.

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Table V is applied to make an approximate model of each response

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Which is a set of statistical and mathematical techniques used to find the best fitting response of the physical system through experiment or simulation, is used as an optimization method.

The response surface of each approximate model is shown in Fig.

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The final results of the optimization are given in Table VI, and the accuracy of the models is verified through the table.

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Test Results And Discussion

The fabricated IPMSM are exhibited in Fig. 4. In order to verify the performance of the IPMSM, tests are carried out as shown in Fig. 5.

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Fig. 4 Configurations of fabricated IPMSM. (a) Rotor. (b) Rotor assembly. (c) Air blower.

Fig. 5. Testing apparatus for air-blower system test.

Test results of the air-blower system. (a) Input current. (b) System efficiency. (c) Air-blower efficiency.

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Losses obtained by characteristics analysis. (a) At 10 000 r/min (top) and 30 000 r/min (bottom). (b) At 20 000 r/min (top) and 40 000 r/min (bottom).

The efficiency of the IPMSM is high due to a relatively small core loss before 25 000 r/min. After the speed, as the load rises, the influence of copper loss is dominant due to an increase of input current. At this time, the mechanical loss of the SPMSM and IPMSM is not considered, because their rotor sizes are the same.

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Conclusion

Even though current vector control is required to obtain maximum torque, the overall efficiency measured in the IPMSM is better than that of the SPMSM. In addition, the amount of permanent magnet actually used in the IPMSM is reduced by approximately 53% than the SPMSM.

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References [1] A. Binder, T. Schneider, and M. Klohr, “Fixation of buried and surface-mounted magnets

in high-speed permanent magnet synchronousmachines,” IEEE Trans. Ind. Appl., vol. 42, no. 4, pp. 1031–1037, Jul./Aug. 2006.

[2] A. M. EL-Refaie, R. Manzke, and T. M. Jahns, “Application of bi-statemagnetic material to automotive offset-couple IPM starter/alternatormachine,” IEEE Trans. Ind. Appl.., vol. 40, no. 3, pp. 717–725, May/Jun. 2004.

[3] E. C. Lovelace, T. M. Jahns, T. A. Keim, and J. H. Lang, “Mechanicaldesign considerations for conventionally laminated, high-speed, interiorPM synchronous machine rotors,” IEEE Trans. Ind. Appl., vol. 40,no. 3, pp. 806–812, May/Jun. 2004.

[4] J. M. Park, S. I. Kim, J. P. Hong, and J. H. Lee, “Rotor design ontorque ripple reduction for a synchronous reluctance motor with concentratedwinding using response surface methodology,” IEEE Trans.Magn., vol. 42, no. 10, pp. 3479–3481, Oct. 2006.

[5] B. H. Lee, S. O. Kwon, T. Sun, J. P. Hong, G. H. Lee, and J. Hur,“Modeling of core loss resistance for d-q equivalent circuit analysis ofIPMSM considering harmonic linkage flux,” IEEE Trans. Magn., vol.47, no. 5, pp. 1066–1069, May 2011.

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Thanks for listening

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凸極效應

若永磁馬達的磁鐵埋在轉子中，磁鐵可以受到轉子的保護，在高速運轉時不會有磁鐵脫落的問題但轉子需有一空洞要置入磁鐵，而轉子的材質為矽鋼，磁導率遠高於磁鐵，因此磁鐵部份可視為一個額外的氣隙，轉子和定子間的氣隙會有周期性的變化，即凸極效應，因此產生的轉矩中有磁阻轉矩成份，其效率較高。

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