Radial Flux PMSM Design and Optimization

Liping Zheng

02/21/2003

Radial Flux PMSM Structure

Stator Outer Diameter = 30mm

Stator Inner Diameter = 21.7mm

Rotor Diameter = 14mm

PM Width = 7mm

PM Height = 13mm

PM Material=NdFeB39H

Motor Active Length = 43mm

Laminated low loss core

PM

Shaft

Winding

Winding Method

2-pole, 3-phase. 5 coils/phase/pole. Two layer lap winding. Pitch: 23/30. First coil: btm1->top12. Round copper wire –AWG14. Bare diameter: 0.0641in (1.63mm). Diameter after insulation: 0.0673in (1.71mm).

Fractional (Distributed) Winding The coils of a fractional winding within each pole

region are distributed over many pairs of slots. Distribution factor:

Reduce the harmonics of the spatial mmf distribution.

)2/sin(

)2/sin(es

es

ci

poled q

q

Eq

Ek

957.0)30/sin(5

)30/5sin(

dk

Short-pitching Use short-pitching to further reduce harmonics. The pitch factor for the fundamental:

For nth harmonic pitch factor.

3rd and 9th are not harmful.

5th and 7th have negative effect to the torque.

2sin

2sin

WnnK pn

2sin

2sin1

WK p

W=23 τ=30

Kp

0.891

0.156

0.707

0.988

0.454

0.934

0.454

0.259

0.839

0.988

0.966

0.707

0.259

0.259

0.707

BEMF of Fractional & Concentrated Winding

Fractional winding and short-pitching reduce the harmonics greatly.

Simulated BEMF

Simulated Airgap Flux

Arnon 5- BH Curve

Arnon 5- Loss

45W/lb

Efficiency

Copper Loss 16.8W

Iron Loss 11W

Estimated Stray Loss 11W

Windage Loss 21W

Motor Efficiency* 97%

Control Efficiency 95%

Total Efficiency 92%

* Bearing loss is not included.

Shaft with the Bearings for Test

Motor length = 43mm

End length = 20mm

Total length = 83mm

Conclusion

Have modified the winding structure and re-adjusted the pitch factor.

Have selected the high energy NdFeB39H.The motor active length is reduced from

50mm to 43mm.Have considered the ball bearing

connection structure for the test purpose. Will do mechanical drawing using pro/E in

the next step.