Flux Conference 2012 Analysis of a Tubular PM Motor with Integrated Contactless Energy Transfer D.C.J. Krop, MSc R.L.J. Sprangers MSc Prof. Dr. E.A. Lomonova Date : 18 October 2012
Introduction Eindhoven University of Technology Electromechanics and Power Electronics group 2
Introduction Rotary Planar Tubular Linear Multi-air gap 6-DoF structures 3
Introduction Role of Finite Element Analysis (FEA) in our research: Research Proof-of-principle Validation of complex (semi) analytical methods Validation and fine-tuning of final design 4
Actuator topology Integrated topology Decomposed topology: Transformer (left) Motor (right) 5
Actuator topology Orientation of the magnetic fields (simplified) Motor flux Transformer flux 6
Problem definition Specifications 2D analytical models Analytical optimization Fast and accurate Linear and geometry has to be simplified Optimized design 2D/3D validation and fine-tuning 7
Design specifications Continuous power transfer: Minimum peak force: Magnet temperature: Maximum temperature: Secondary voltage: Winding ratio: Transformer frequency: Flux density (transformer): Flux density (motor): Current density (transformer): Current density (motor): S = 800 VA F > 250 N Tmag < 80 C Tmax = 120 C Vsec = 180 V 1:1 ftrans = 5 khz Btrans = 100 mt Bmot = 1.2 T Jtrans = 2.4 A/mm2 Jmot = 2.2 A/mm2 8
2 dependent 2D analytical Fourier models Limitations: Topology is essentially 3D Magnetic field is only known in the air gap and magnets Does not allow for nonlinear soft-magnetic core material Cross-coupling effects due to superimposed fields not accounted for No proximity effect 9
3D FEM flux model Advantages of Flux 3D Nonlinear isotropic material properties Non-simplified geometry Eddy current losses calculation in PMs due to 5 khz transformer flux with the AC solver Problems arising for this topology Double periodicity (circumferential and axial) cannot be accounted for AC solver cannot handle nonlinear core and PMs Transient simulation of full topology requires too many time steps due to discrepancy in frequency (84 Hz for motor and 5 khz for transformer) 10
Verification of analytically calculated force: 3D periodic nonlinear magnetostatic Flux model Periodic boundary conditions 3D magnetostatic solver Nonlinear core material 2 Periodic boundaries 2 Tangential boundaries 2 Mechanical sets Meshed coils Tangential field boundary conditions 11
Minimization of end-effect cogging 20 wend=3.6 mm 15 wend=3.7 mm 2D Magnetostatic solver Nonlinear core material 3 Mechanical sets Force calculation on moving mechanical set wend=3.8 mm 10 wend=3.9 mm F [N] 5 0-5 -10-15 -20-25 0 1 2 3 4 x [mm] 12 5 6
Flux linkage variation of the transformer vs. position and phase current density 2 3D Magnetostatic solver Nonlinear core material 2 Periodic boundaries 3 Mechanical sets 10 Non-meshed coils Phase current density sweep Calculation of the transformer flux in the θdirection Jph= 0 Amm-2 1.5 [%] 1 0.5 0-0.5-1 -1.5-6 Jph= 1 Amm-2 Jph= 2 Amm-2 Jph= 3 Amm-2 Jph= 4 Amm-2-4 -2 0 x [mm] 13 2 4 6
Thrust force vs. position and phase current density 600 Jph= 0 Amm-2 Jph= 1 Amm-2 500 Jph= 2 Amm-2 400 Jph= 3 Amm-2 Jph= 4 Amm-2 F [N] 300 200 100 0-100 -6-4 -2 0 x [mm] 14 2 4 6
Thrust force vs. magnetization flux density field of the transformer at nominal phase current 325 Bt = 0.0 T 320 Bt = 0.2 T Bt = 0.4 T 315 Bt = 0.6 T F [N] 310 Bt = 0.8 T Bt = 1.0 T 305 300 295 290 285 280-6 -4-2 0 x [mm] 15 2 4 6
Eddy current losses in the PMs due to transformer leakage field at full power (800 W) 19.856 19.854 Ploss,PM [W] 19.852 19.85 19.848 19.846 3D AC steady-state solver No PM magnetization term Linear core material 2 Periodic boundaries 2 Normal boundaries 19.844 19.842-2000 -1500-1000 -500 0 x [mm] 16 500 1000 1500 2000
Flux 2D proximity effect model Primary transformer winding experiences proximity effect! 17
Flux 2D proximity effect results Primary transformer winding experiences proximity effect! Primary ohmic loss versus wire diameter 4 Ohmic loss (W) 3 2 1 0 0.6 0.8 1 Wire diameter (m) 18 1.2
Steady state thermal model results Motor force (analytical versus FEA): 19
Conclusion Complex topologies give rise to additional modeling problems Magnetostatic Flux 3D modeling can predict motor performance Cross-coupling between motor and transformer operation can be calculated from the motor model Steady State Flux 2D modeling can predict proximity effect in primary winding Primary winding diameter can be optimized from the proximity effect model 20
Question? 21