1 Florence Libert NORPIE 2004 Design Study of Different Direct-Driven Permanent–Magnet Motors for a Low Speed Application

2 Florence Libert NORPIE 2004 The goal of the study is to compare different designs of direct-driven permanent magnet (PM) motors that should replace an induction motor and its gearbox for an industrial application requiring 5 kW and 50 rpm. Low Speed PM Drives

3 Florence Libert NORPIE 2004 Content The investigated rotor configurations Advantages and drawbacks of the investigated configurations The design procedure Results and comparisons

4 Florence Libert NORPIE 2004 The investigated rotor configurations

5 Florence Libert NORPIE 2004 Rotors with surface-mounted PM

6 Florence Libert NORPIE 2004 Rotors with buried PM

7 Florence Libert NORPIE 2004 Advantages and drawbacks of the investigated configurations For buried PM: »Flux concentration »Protection of the magnets »Reluctance torque Drawbacks: »Many magnets for V-shape PM »Many pieces for Tangential PM rotor giving production difficulties

8 Florence Libert NORPIE 2004 Design procedure followed for a low speed PM motor

9 Florence Libert NORPIE 2004

10 Florence Libert NORPIE 2004 Phasor diagram

11 Florence Libert NORPIE 2004

12 Florence Libert NORPIE 2004

13 Florence Libert NORPIE 2004 Result and comparison Torque ripple Weight and choice of the pole number Chosen designs

14 Florence Libert NORPIE 2004 Active weight as a function of the pole numbers for different PM motor designs

15 Florence Libert NORPIE 2004 Fundamental of flux density in the airgap B  and length for different configurations and p=50 SMPM Outer rotor SMPM Inset PM Tangentially magnetized PM B  [T] Length [mm]

16 Florence Libert NORPIE 2004 Ratio between the torque ripple and the mean torque SMPM Outer rotor SMPM Inset PM Tangentially magnetized PM p= p= p=

17 Florence Libert NORPIE 2004 Geometries of 60-pole outer rotor PM and tangentially magnetized PM optimal designs

18 Florence Libert NORPIE 2004 Comparison between outer rotor design and buried magnet design for p=60 Outer rotor SMPM Tangentially magnetized PM Total active weight [kg] Magnet weight [kg]5.5 Length [mm] Fundamental of airgap flux density B  [T] Mean torque [p.u] Efficiency [%]

19 Florence Libert NORPIE 2004 Conclusion Rotor with V-shape magnets is not appropriate for designs with high pole numbers Outer rotor designs are lighter than inner rotor designs Inset PM motors are slightly lighter than SMPM thanks to the reluctance torque High torque ripple when q=1 demands to consider other winding configurations Tangentially magnetized PM designs are the lightest due to the flux concentration

20 Florence Libert NORPIE 2004 Conclusion It is possible to design direct-driven PM motors with better efficiency and less weight than the induction motor and its gearbox A prototype is required to confirm experimentally the results

21 Florence Libert NORPIE 2004 Thank you for your attention