Soft Magnetic Composite Axial Flux Seven-Phase Machine F. Locment, E. Semail and F. Piriou Laboratory of Power Electronic of Lille 1/21 ENSAM & University of Lille, France
Soft Magnetic Composite Axial Flux Seven-Phase Machine Outline I> Introduction II> Machine: 3d-modelling and experimental results 6 EXPERIMENTAL 3D-FEM Cogging torque (Nm) 4 2 0-2 -4-6 0 5 10 15 Position ( ) III> Drive : experimental torque DC 0 drive motor Torque Repartition Tref im1qref of reference 0 torques im2qref 0 im3qref 2/21 R(θ) +- +- R(9θ) +- +- cospθ sin pθ R(θ) = sin pθ cospθ R(3θ) +- M3α M3β M2α M2β vm2βref R-1(θ) im2d im2q im3q vbref vcref [C7 ] vdref PWM 7-Phase veref VSI AFPM vfref vgref vm3βref im1α M1α M1β im1β M3α M3β M2α M2β im2α R-1(9θ) [C7 ] 1 im2β im3α R-1(3θ) im3β ABCDEFG encoder varef ABCDEFG im3d Optical M1α M1β vm1βref vm3αref im1q AFPM vm1αref vm2αref im1d transducer IV> Conclusion +- θ ia,ib,ic,id,ie,if,ig
I. Introduction Why such a seven-phase axial-flux Machine? Axial or radial Flux Machine? Earliest machines are axial-flux machines (Faraday 1831) Reasons for shelving axial-flux machines? Manufacturing difficulties and corresponding high costs : for control of uniform air gap (axial magnetic attraction) for laminated sheets and slot of the stator 3/21 Iron lamination enrolled and compacted as a spiral
I. Introduction Why a SMC Axial Flux Seven-Phase Machine? Axial or radial Flux Machine? 1>Earliest machines are axial-flux machines (Faraday 1831) 2>Reasons for shelving axial-flux machines? Manufacturing difficulties and corresponding high costs : for control of uniform air gap (axial magnetic attraction) for laminated sheets and slot of the stator core 4/21 Not easy to cut slots in a stator made with iron lamination enrolled and compacted as a spiral
I. Introduction Why a SMC Axial Flux Seven-Phase Machine? Axial or radial Flux Machine? 1>Earliest machines are axial-flux machines (Faraday 1831) 2>Reasons for shelving axial-flux machines? Manufacturing difficulties and corresponding high costs : for control of uniform air gap (axial magnetic attraction) for laminated sheets and teeth of the stator for windings arrangement : asymmetry 5/21 Problem of space with end windings at inner radius
I. Introduction Consequences of manufacturing difficulties 1> Use of Soft Magnetic Composite? easy to cut slots 3D magnetic property New process of fabrication 6/21
I. Introduction Consequences of manufacturing difficulties 2> Simple arrangements of the winding Consequence for 3-phase axial machine Toroidal winding No distributed winding flux linked by one phase is not sinusoidal Non-sinusoidal Electromotive forces except with special shapes of magnets Concentrated winding 7/21 No performant vector control with weak torque ripples
I. Introduction Two interesting points of multiphase machines: 1. performant vector control with weak torque ripple even with non-sinusoidal emf 2. intrinsically fault-tolerant machine (already used in electrical ship, future offshore wind generator?) To sum up For performant vector control (torque quality) Multiphase machines impose less constraints on the designer than three-phase machines 8/21 It is particularly interesting for axial-flux machines.
Characteristics of the machine 9/21
II. Characteristics of the machine Two rotors, 6 poles, a SMC stator with 42 slots ROTORS STATOR MAGNETS COILS 189mm 287mm 10/21 ATOMET EM1(QMP) NdFeB N48
II. Characteristics of the machine 11/21 Φ S S (a) NN type N N Nominal power at 750 rpm (kw) Nominal Torque with 50 C in coil (Nm) Nominal Speed (rpm) S Φ N (b) NS type N S Seven phases with toroidal winding 1 slot/pole/phase No filtering effect 750 Nominal current at 65 Nm (A) 5 4/5 arc pole for the magnet repartition: cancellation of the fifth harmonic of emf shift of one slot (mechanical angle 4.3 ) between the two rotors : reduction of the cogging torque 5 65
II. Characteristics of the machine Determination of the characteristics? 1>Classical analytical modelling by determination of average flux magnetic density in airgap for determination : of main geometrical characteristics rms value of main harmonic of emf. 2> 3D-Finite Element Method for determination of more sensitive characteristics: cogging torque ; 12/21 harmonics of flux magnetic density and emf ;
II. Characteristics of the machine With a shift of 4.3 between the two rotors 60 airgap magnetic flux density by 3D-FEM (Carmel) Electromotive force for 1rd/s 6 % of error on the first harmonic Electromotive force 13/21
II. Characteristics of the machine Cogging Torque 0.25 p.u. 3D-FEM cogging torque Peak value 0.06 in p.u. without and with shift between rotors Comparison of cogging torques with shift between rotors 14/21 (experimental and simulation)
Characteristics of the drive 15/21
III. Characteristics of the drive 7-leg Voltage Source Inverter Dspace 1005 controller board 7-phase axial-flux Supply electronic charge 16/21 Back-ground with DC motor, seven-phase machine and torque transducer (MAGTROL TM211)
III. Characteristics of the drive Multi-machine modelling of a seven-phase machine Well known Generalization Wye-coupled 3-phase machine Wye-coupled 7-phase machine ONE 2-phase machine (d,q) Sinusoidal emf required for 2-phase machine for vector control THREE 2-phase machines mechanically and electrically coupled Sinusoidal emf required for EACH 2-phase machine 17/21
III. Characteristics of the drive Fictitious 2-phase machines M1 M2 M3 Families of odd harmonics 1, 13, 15, 27,, 5, 9, 19, 23,, 3, 11, 17, 25,, 1>Only one harmonic/2-phase fictitious machine (as for classical 3-phase machine) Back-emf (%) 100 80 60 40 20 M1 M3 M2 0 0 1 3 5 7 9 11 13 15 17 19 21 23 Order of harmonics EXPERIMENTAL 3D-FEM Ideal emf with only the 1st, the 3rd and the 5th harmonic 18/21 2>For good ability in open-phase fault operation smallest emf for M2
III. Characteristics of the drive Synoptic of the 7-phase vector control T ref Repartition of reference torques 0 i M1qref 0 i M2qref 0 i M3qref + - + - + - + - + - + - i M1d i M1q R(θ) R(9θ) R(3θ) R -1 (θ) v M1αref v M1βref v M2αref v M2βref v M3αref v M3βref i M1α M1 i M1β M1α M1β M2α M2β M3α M3β [ ] C 7 ABCDEFG M1α M1β M2α M2β M3α M3β v Aref v Bref v Cref v Dref v Eref v Fref v Gref PWM VSI 7-Phase AFPM 19/21 [ C 7 ] = cospθ sinpθ R( θ ) = sinpθ cospθ 1 1 0 1 0 1 0 2 1 2π 2π 4 π 4 π 6 π 6 π cos sin cos sin cos sin 2 7 7 7 7 7 7 1 4 π 4π 8 π 8 π 12π 12π cos sin cos sin cos sin 2 7 7 7 7 7 7 2 1 6 π 6 π 12π 12π 18π 18π cos sin cos sin cos sin 7 2 7 7 7 7 7 7 1 8 π 8 π 16 π 16 π 24 π 24 π cos sin cos sin cos sin 2 7 7 7 7 7 7 1 10π 10 π 20π 20 π 30π 30π cos sin cos sin cos sin 2 7 7 7 7 7 7 1 12π 12π 24 π 24 π 36 π 36π cos sin cos sin cos sin 2 7 7 7 7 7 7 i M2d i M2q i M3d i M3q R -1 (9θ) R -1 (3θ) θ i M2α i M2β i M3α M3 i M3β [ C ] 1 7 ABCDEFG i A,i B,i C,i D,i E,i F,i G
III. Characteristics of the drive Currents in one phase for two cases Measured mechanical torques Only M1 machine supplied - 65 Nm -70 Nm 20/21 M1 and M3 supplied (1st and 3rd harmonics) Amplitude of 0.04 p.u. for pulsating torque
IV. Conclusion If vector control and weak torque ripples are required If axial spatial constraints are imposed Prototype Multiphase axial-flux machines are very interesting because sinusoidal emfs are not necessary. For the quality of torque, the seven-phase drive presents good characteristics in agreement with predeterminations obtained by 3D-FEM Performance of the drive with two open phases? 21/21 Other paper in poster session: «A Vector Controlled Axial-flux Seven-phase Machine in Fault Operation
IV. Conclusion If vector control and weak torque ripples are required If axial spatial constraints are imposed Multiphase axial-flux machines are very interesting because sinusoidal emfs are not necessary. For the quality of torque, the seven-phase drive presents good characteristics in agreement with predeterminations obtained by 3D-FEM For the efficiency of the drive and its thermal limits, further investigations on materials and modelling must be achieved to predict the obtained results. 22/21