The eddy current losses in all PMs of PMAFM-ISA designs with differently seg-mentation of PM at no-load and 60 min−1are listed in Table 5.11. It is apparent that the PM segmentation along the radial direction leads to a more even area of PM segments and can achieve less losses. Compared with the direction of seg-mentation, the number of PM segments or rather the area of per segment is more dominant. For instance, a PM consisting of 6 segments can generate nearly only half of the PM eddy current losses compared with PMAFM-ISA design 20. The informative efficiency map of PMAFM-ISA 25 is illustrated in Fig. 5.20.
Version Segmentation Number of
PM losses method segments
PMAFM-ISA 20 - - 15.65 W
PMAFM-ISA 21 circumferential 2 12.17 W
PMAFM-ISA 22 circumferential 3 9.46 W
PMAFM-ISA 23 radial 2 10.70 W
PMAFM-ISA 24 2D 4 8.84 W
PMAFM-ISA 25 2D 6 7.28 W
Table 5.11. PMAFM-ISA designs with different PM segmentation
With the help of PM segmentation, the efficiency of PMAFM-ISA 25 is ob-viously improved and the peak efficiency increases more than 1.5 % compared with PMAFM-ISA 20. In addition, the reduction of the peak torque at low speed area becomes much smaller and the speed-torque-curve becomes much flatter.
5.4 Final electromagnetic design and validation
Efficiencyη/%
Rotational speed n / min−1
TorqueT/Nm
92 92
60 60 60
80 80 85 8085
85
90 90 90
92 92 92
92 94
94
94
94
94 94
95 95 95
95.5 95.5
96
95.5 95.5
95.5 95 96
0 1000 2000 3000 4000 5000 6000 0
20 40 60 80 100
0 50 100 150 200 250
Figure 5.20. Efficiency map ofPMAFM-ISA 25with 2D PM-segmentation
• Rounding of SMC components to reduce the stress concentration resulted from manufacturing and to avoid damage of winding isolation.
The ultimately manufactured stator segment and rotor yoke element are illus-trated in Fig. 5.21.
(a) Stator segments (b) Rotor yoke component
Figure 5.21. Manufactured SMC parts
It is apparent that the inner and outer edges of the rotor yoke are 0.1 mm higher than the rest part to realize the necessary gap for the adhesive.
Although the cross sectional area is reduced due to the rounding of the stator segments and the reluctance becomes larger due to the adhesive gap between PM and rotor yoke, their influence on the electromagnetic properties of PMAFM-ISA is extremely limited. The efficiency map of the final electromagnetic design is illustrated in Fig. 5.22.
Efficiencyη/%
Rotational speed n / min−1
TorqueT/Nm 92
92
93 93
90 90
60 60 60
80 80
85 85 85 85
90 90 90 90
92 92
92
93 93
93
93 94
94 94
94 94.5
94.5
94.5
0 1000 2000 3000 4000 5000 6000 0
20 40 60 80 100
0 50 100 150 200 250
Figure 5.22. Efficiency map of the final design of PMAFM-ISA without PM-segmentation
The PM has the relatively low thickness equal to 2.2 mm and its demagnetization should be carefully investigated. As shown in Fig. 5.23, the working point of PM at 160◦C and Idequalling 640 A, which is 1.5 times of the maximum phase current, is marked with a small red circle. It can be seen that even for the worst case, the flux density of PM is high enough and the demagnetization doesn’t occur.
At last, the most important parameters of the final electromagnetic design of PMAFM-ISA are summarized in Table 5.12.
5.4 Final electromagnetic design and validation
Working point 180◦C 160◦C 150◦C 120◦C 100◦C 60◦C 20◦C
Field strength H / kA m−1
FluxdensityB/T
−2000 −1500 −1000 −500 0
−1.0
−0.5 0.0 0.5 1.0 1.5
Figure 5.23. Demagnetization test of PM in final design
Symbol Description Value Unit
Da active outer diameter 301 mm
Di active inner diameter 209 mm
Lmotor active total axial length 75 mm
Nsegments Number of stator segments 36
-p Number of pole pairs 12
-Lg axial length of air gap 1 mm
Lshoe axial length of stator shoe 5 mm
Lbar axial length of stator bar 39.6 mm
Lyoke axial length of rotor yoke 9.5 mm
Nyoke Number of segments per rotor yoke 9
-LPM axial length of PM 2.2 mm
αslot ratio of slot opening to segments distance 0.7
-αPM pole arc to pole pitch ratio 0.7 mm
θPM skewing angle of PM 18 °
Nphase Number of parallel branches of each phase 6
-Bcoil width of the coil around a segment 3.80 mm wcoil Number of turns per coil around a segment 26
-Table 5.12. Main parameters of the electromagnetic design of PMAFM-ISA
6
Electromagnetic Design of PMTFM-CP
Besides the PMAFM-ISA, the permanent magnet excited transverse flux ma-chine with claw poles (PMTFM-CP) is another promising topology for the appli-cation of SMC, which is distinguished by its high pole pair number and torque density [O6, O7, S8]. In PMTFM-CP, the permanent magnets with opposite circumferential magnetization directions are embedded in the rotor. All the stator segments are located on one side of the rotor and a ring winding is lo-cated within the stator segments for each phase. Therefore, the PMTFM-CP can achieve high torque density and relatively simple mechanical construction simultaneously [S9, S10].
Assuming the phases of PMTFM-CP are magnetic decoupled from each other, it is only necessary to analyse one pole pair model of one phase considering the magnetic symmetry around the rotational axis. For instance, the meshed model and the FEM results at no-load are illustrated in Fig. 6.1. It can be clearly seen the magnetic flux flows three-dimensionally in the PMTFM-CP. The main magnetic flux marked with small arrows from the PM is concentrated in the rotor concentrator and then flows through the air gap, the stator claws, the teeth on the front side, the stator yoke, the teeth, the claws, and the air gap on the rear side, which finally flows back to the PMs in the rotor. To realize the conduction of 3D magnetic flux, the SMC material is used to manufacture the complex stator and the rotor flux concentrator.
(a) One phase model of PMTFM-CP
Stator yoke
Tooth
Ring winding
Rotor Claw segment
PM
PM
(b) FEM model of one pole-pair
0.0 0.5 1.0 1.5 2.0 2.5
FluxdensityB/T
(c) B-Field (d) Magnetic flux
Figure 6.1. Structure and FEM results of a PMTFM-CP
The chapter is organized as follows. At first, the free geometric parameters of PMTFM-CP, the optimization objectives and design procedure are presented.
Subsequently, the electromagnetic design of PMTFM-CP has been carried out according to the design procedure.