Optimierung von Wirkungsgrad und elektromagnetisch erzeugten Geräuschen bei elektrischen Antrieben in Kraftfahrzeugen

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1 Optimierung von Wirkungsgrad und elektromagnetisch erzeugten Geräuschen bei elektrischen Antrieben in Kraftfahrzeugen Dieter Gerling Audi-Forum elektrische Kleinantriebe im Fahrzeug Ingolstadt,

2 Inhalt Einleitung Vergleich von E-Maschinen mit konzentrierten Spulen und verteilter Wicklung Beispiel 1: ISG (PM-Maschine) Beispiel 2: ISCAD (Asynchronmaschine) Zusammenfassung 2

3 Einleitung Wesentliche Anforderungen an E-Antriebe im Kfz Kosten Wirkungsgrad Wichtigkeit einzelner Eigenschaften hängt von der Anwendung ab Geräusch, Gewicht, etc. 3

4 Distributed Winding Concentrated Winding advantages nearly sinusoidal air-gap field disadvantages high number of slots per pole large end windings high parasitic end winding effects high copper losses high production costs 4 advantages compact design simple manufacturing short end winding with low complexity low copper losses disadvantages high number of space harmonics with high amplitude (resulting in rotor losses, vibration and noise)

5 Distributed Winding Concentrated Winding working harmonic working harmonic radial forces noise losses 5

6 Beispiel 1: ISG (PM-Maschine) Wirkungsgrad und akustische Geräusche 3-Teeth/2-Poles FSCW PM ISG Machine required torque Torque [Nm] delivered torque Area characterized with high rotor losses and temperature problems nb nmax speed [rpm] Actual Machine Problems: As result of high harmonic contents, the 3-Teeth/2-Poles FSCW is characterized with high rotor losses and thermal problems at high speed/power applications 6

7 Beispiel 1: ISG (PM-Maschine) Wirkungsgrad und akustische Geräusche Alternative Solution Conventional 3-Teeth/2-Poles Winding Tooth concentrated coils Double layer, +A +B +C 7 New 18-Teeth/1-Poles Winding Tooth concentrated coils Two winding systems: A1B1C1 & A2B2C2 Three-phase machine with star&delta winding combination

8 Beispiel 1: ISG (PM-Maschine) MMF Characteristics 1. Conventional 3T/2P Winding MMF [ p.u. ] MMF [ p.u. ] theta [rad. degree] theta [rad. degree] 1 5*(3T/2P) 18T/1P 2. New 18T/1P Winding MMF [ p.u. ] Harmonic Order

9 Beispiel 1: ISG (PM-Maschine) Wirkungsgrad und akustische Geräusche Winding Factor Winding factor [ % ] *(3T/2P) 18T/1P Conventional 3-Teeth/2-Poles Winding 86.6% winding factor, high harmonic contents New 18-Teeth/1-Poles Winding 76% winding factor, low harmonic contents Harmonic Order 9

10 Beispiel 1: ISG (PM-Maschine) Wirkungsgrad und akustische Geräusche Requirements Volume Data - Stator outer diameter, Da_s = 3mm - Rotor outer diameter, Da_r = 24mm - Rotor shaft diameter, Da_sh = 2mm - Active length, Lstk = 63mm - Gap length, gap = 1mm - Number of pole pairs, p = 1 Electromechanical Data - Maximal torque, Tmax = 27Nm - Maximal current, Imax = 25Arms - Maximal speed, n_max = 6 rpm - Nominal speed, n_n = 2 rpm - DC battery voltage, U_DC = 3 V Torque, Power Tmax Pmax 2 rpm 6 rpm 1

11 Beispiel 1: ISG (PM-Maschine) Wirkungsgrad und akustische Geräusche Electromagnetic Torque T [Nm] I =25Arms, delta=25 (base speed) 8 Conv. 3T/2P New 36T/2P Conventional 3T/2P Design High torque ripple rotor position [ el. degree ] Stator/Rotor skewing is required - High manufacturing costs - Effective torque reduction about 5% 11 T [Nm] 18 I =25Arms, delta=7 (field weakening) Conv. 3T/2P 6 New 36T/2P 3 Proposed 36T/2P Design Low torque ripple rotor position [ el. degree ] No skewing is required

12 Beispiel 1: ISG (PM-Maschine) Wirkungsgrad und akustische Geräusche Field Weakening Capability T [Nm] Torque-speed, I = 25Arms Conv. 3T/2P New 36T/2P Pmech [kw] Pmech-speed, I = 25Arms 8 6 Conv. 3T/2P New 36T/2P speed [rpm] speed [rpm] Proposed 36T/2P Design Increase of power by 13% 12

13 Beispiel 1: ISG (PM-Maschine) Wirkungsgrad und akustische Geräusche Air-Gap Flux Density and Radial Forces Air-gap flux-density B [ T ] T2P 36T2P F [ N/m² ] 1 x 15 5 Magnetic radial forces 3T2P 36T2P B [ T ] theta [degree] T2P 36T2P F [ N/m² ] theta [degree] 3 x T2P 36T2P Space Harmonics Space Harmonics 1 f ( θ, t) = B ( θ, t ) + B ( θ, t) rad s r, PM s r, S s 2µ m= rad ( θ ω ϕ ) m = Fˆ cos m t s m m 2 13 Conv. 3T/2P: m =,1, 2, 3 New 36T/2P: m =, 16, 2, (4)

14 Beispiel 1: ISG (PM-Maschine) Wirkungsgrad und akustische Geräusche Radial Forces F [ N/m² ] F [ N/m² ] 2.6 x T2P 36T2P time [ms] mode- 3T2P 36T2P p x f f [[Hz] ] R F [ N/m² ] F [ N/m² ] 5 x T2P 36T2P time [ms] 4 x mode-2 3T2P 36T2P px f f [ [Hz] ] R 14

15 Beispiel 1: ISG (PM-Maschine) Wirkungsgrad und akustische Geräusche Magnet Losses Conventional 3T/2P Design New 36T/2P Design Proposed 36T/2P Design No magnet segmentation necessary 15

16 Beispiel 1: ISCAD (Asynchronmaschine) Die-Casted Stator Winding 16

17 Beispiel 1: ISCAD (Asynchronmaschine) Electrical Machine Wound Copper Coils Poor Utilization High Thermal Resistance Complex Production Inverter HV Ratings (6 V) 3 Half Bridges PCB/DBC Isolated Heatsink Electrical System DC Low Wiring Cross-Sections Insulation Monitoring 2-Pole Circuit Breaker Electric Field Shielding + - Battery Voltage up to 4 V Many Cells in Series Few Paths in Parallel Isolated BMS 17

18 Beispiel 1: ISCAD (Asynchronmaschine) Electrical Machine Die-Cast Alu Bars Perfect Utilization Direct Cooling via Ring Minimum Production Cost Inverter LV Ratings (below 6 V) 6 Half Bridges Supply of Every Phase Stator Bars as Heatsink Electrical System DC Large Wiring Cross-Sections Less Safety Effort Magnetic Field Shielding Aluminum Instead of Copper 3% cost (June 215) 3% mass density Battery Voltage below 6 V Few Cells in Series Many Paths in Parallel High Redundancy Non-Isolated DCDC for 12 V

19 Beispiel 1: ISCAD (Asynchronmaschine) Electrical Machine Inverter Pole Pair Switching Torque/Speed Scaling Multiple Efficiency Maps Electric gearbox Excellent partial load efficiency MOSFETs instead of IGBTs Synchronous Rectifying R DSon instead of constant V F 19

20 Beispiel 1: ISCAD (Asynchronmaschine) Evaluation of Machine and Inverter Losses ISCAD Improves Efficiency by 15% to 2% 2

21 Beispiel 1: ISCAD (Asynchronmaschine) MMF Characteristics (18 slots per pole pair) Conv. Winding New Winding 1 Conv. Winding New Winding MMF [ p.u. ] MMF [ p.u. ] theta [rad. degree] Space Harmonics 21

22 Beispiel 1: ISCAD (Asynchronmaschine) electrical machine: benchmark with Tesla Model S ISCAD ASM Tesla ASM Comparison of results 375 V * Total Joule loses for the stator cage winding including skin and proximity effect 22

23 Beispiel 1: ISCAD (Asynchronmaschine) 7 Stator-slot T=6Nm, n=53 rpm, hc = 2W/(Km²) Tesla ASM ISCAD ASM T [ C ] ISCAD-asm tesla-asm time [s] 6 Rotor-slot Losses: P P Losses, Tesla Losses, ISCAD = 2 T [ C ] ISCAD-asm tesla-asm Loss density: p p * Losses, Tesla * Losses, ISCAD time [s]

24 Zusammenfassung Wirkungsgrad und akustische Geräusche Die Anforderungen nach Kosten, Wirkungsgrad und Geräusch/Gewicht/etc. müssen sich nicht widersprechen Wegen der hohen Anforderungen muss die Optimierung applikationsspezifisch durchgeführt werden Beispiel 1: ISG als PM-Motor Beispiel 2: ISCAD als Asynchronmaschine 24