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SPARK Introduction | February, 2016 | 1

New Frontiers of Brushless PMMotor Technology

Dan M. Ionel, Ph.D., IEEE [email protected]

CWIEME Berlin, May 11, 2016

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New Frontiers of Brushless PM Motor Technology | CWIEME Berlin, May 2016 | 2

Dr. Dan M. Ionel

Dan M. Ionel is Professor of Electrical Engineering and L. Stanley Pigman Chair in Power at University of Kentucky in Lexington, KY. Previously, he held dual appointments in industry, as Chief Engineer with Regal Beloit Corp and before as Chief Scientist with Vestas Wind Turbines, and in academia, as Visiting and Research Professor with University of Wisconsin and Marquette University in Milwaukee, WI.

Dr. Ionel has more than 25 years of engineering experience and has designed electric machines and drives with power ratings between 0.002 and 10,000hp. He holds more than 30 patents and has published more than 100 journal and conference papers, including two winners of IEEE best paper awards. Dr. Ionel is an IEEE Fellow, the Chair of the IEEE Power and Energy Society Electric Motor Subcommittee, and the General Chair of the 2017 anniversary edition of the IEEE IEMDC Conference.

[email protected]

mailto:[email protected]

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SPARK and PEIK at University of Kentucky (UK)

• UK enjoys a longstanding tradition in electric machines and drives• Early developments on linear and PM motors, and vector control• Many learned machines using the Nasar and Boldea classic books

• PEIK - Power and Energy Institute of Kentucky, launched with large DOE grant in 2010• Core faculty in electric power engineering and many others in related fields• Endowment established and inaugural L. Stanley Pigman Chair started in 2015• On-going research on electric machines and drives, power electronics and systems,

renewable and alternative energy technologies• SPARK and other laboratories• Motor Design Ltd. and ANSYS Inc. strategic partnerships.

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Motor Design Ltd. and Center for Applied Energy Research

Motor Design Ltd. (MDL)• Founded in 1998• Developers of the Motor-CAD & Motor-LAB

software• Engineering and R&D projects for companies

and EU programs• Strategic partner of ANSYS.

Center for Applied Energy Research (CAER)• Established in 1975• One of University of Kentucky’s largest,

stand-alone, multidisciplinary research centers with more than 100 staff

• Fiber Development Laboratory with the largest solution spinning line found in an academic setting in North America

• Renowned research program on nanocarbon composites.

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Outline

1. Introduction

2. How far can we reach with existent materials?• Record-braking motor – Formula E racing cars• Design considerations for industrial applications• Large scale optimization and innovation• Complex duty cycles – multi-physics analysis, including thermal

3. How far will we be able to reach with new materials?• Nanocarbon wires and windings• Material characteristics and manufacturing issues• Electric motor concepts – solar planes and cars• US DOE research program “Next Generation Electric Machines”.

4. Conclusions.

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AIM Motor Introduction

• FIA Formula E started in 2014

• 1 and 5 – Identic cars: Spark-Renault SRT_01E

• 2 – Powertrain and electronics: McLaren Electronics

• 3 – Gearbox: Hewland

• 4 – Battery 200kW: Williams Advanced Engineering

• 6 – Tyres: Michelin.

Source: www.formulae.com

Typical racing car driving cycle for one lap - LeMans

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Comparative Performance

Motor Type Torque(Nm)

Mass(kg)

TRW(Nm/kg)

Toyota Prius (2004) Interior PM 400 51 7.8

Nissan Leaf Interior PM 300 46 6.5

Tesla S Induction 430 90 4.8

YASA 400 Axial PM 360 24 15.0

AIM Spoke PM 110 9 12.2

Note: Values listed are for peak torque and active material mass.

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Variable Speed Motor Drives – Drive Cycles

• Design considerations• Constant torque• Fan or pump load curve• Duty / driving cycle, incl. transients• Analysis of each design requires analysis for

multiple operating conditions.

8789

90

90

91

91

92

92

92

93

93

93

94

94

94

94.5

94.5

speed, pu

Shaft

torq

ue,

pu

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

85

90

95

efficiency map

2 Hp

4 Hp

6 Hp

8 Hp

10 Hp

Fan load

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Multi-objective Optimization

• Example – Minimize cost andminimize losses (i.e. maximize efficiency)

• Impose constraints

• Quantify the effects on other performance indices

• Thousands of design “candidates” (variations) may have to be analyzed

• Collection of “best compromise” designs

• Definition of a Pareto front: improvement in one objective can only be achieved through a deterioration in another objective, e.g. cost vs. efficiency tradeoffs

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Example Comparative Study – SynRel and PMSynRel• Systematic optimization study with

10,000 candidate designs

• ultra-fast electromagnetic FEA

• differential evolution (DE)

• Typical rating 10hp 1,800rpm

• Induction motor stator core and winding pattern

• Independent variables for rotor geometry (8 or 9) and torque angle

• Comprehensive performance evaluation

• Two objectives: max power factor and min. badness

• One constraint: torque ripple smaller than 20%.

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Synchronous Reluctance (SynRel)

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PM Assisted Synchronous Reluctance (PMSynRel)

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Coupled Electromagnetic and Thermal Analysis

PM machine specific characteristics

• Variation of PM characteristics with temperature

• Torque per amp (torque constant) changes

• Risk of demagnetization, especially in PM hot spots

• Variation of winding conductor characteristics with temperature.

Model TemperatureLosses

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Coupled Electromagnetic and Thermal Analysis – Motor-CAD

Electromagnetics

• Ultra-fast 2D FEA in the abc reference

frame

• Seconds on a state of the art PC

workstation

• Analytical calculations for end effects

Thermal and air-flow

• Equivalent 3D networks

• Calculation time one order of magnitude shorter

than for electromagnetics

Coupling methods

• “Serial”, typ. 6 iterations for each

of Emag and thermal

• “Weak”, typ. only 2 iterations

for Emag and 6-10 for thermal

“Cutting edge”

• Design for complex duty cycles

• Large-scale optimization studies.

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Motor-LAB

Motor-CAD

Therm

Maxwell

Fast Duty Cycle Analysis

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Multi-objective Design Optimization

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AIM Motor Factsheet

• E-motor for racing applications

• Peak torque = 110Nm

• Cont. torque = 70Nm

• Max speed = 12,000rpm

• Power = 73/60 kW

• Max. current = 325Arms

• Field oriented control

• Rare-earth magnets

• Non-oriented thin gage silicon steel

• Liquid and air cooled

• Active materials mass = 9kg

• Manufactured by Equipmake

• Electromagnetic & Thermal design by Motor Design Ltd.

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AIM Motor Stator and Rotor

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AIM Motor Modeling

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Magnetic Field and Copper Losses

Flux-lines and flux-density distribution on (peak) load

0 1000 2000 Frequency [Hz]

P

ac/P

dc

0

90

60

30

AC losses in the stator winding

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Core Losses

• Most core losses located in the stator

• Rotor surface can also have high loss density

• Highest loss concentration occurs in stator teeth and winding.

0

863Pt [W/Kg]

431

Core losses on (peak) load

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Magnet Losses - Sources

• PMs may be electrically conductive

• Conductivity increases 6%-10% for 100C temperature rise

• Higher PM losses in surface SPM than interior IPM

• Surface BPM may require a retainer sleeve with additional losses

• Retainers of glass fibre or carbon fibre

• Eddy-current induced by:

• Space MMF harmonics

• Permeance variation

• Time current harmonics

• Induced eddy-currents create PM losses

• Magnet losses mitigation methods:

• Integer or fractional slots/pole

• Segmentation.

Material Resistivity(ohm*m)

Copper 1.7 x 10-8

Aluminum 2.8 x 10-8

Steel 10 x 10-8

SmCo 1-5 Alloys 50 x 10-8

SmCo 2-17 Alloys 90 x 10-8

NdFeB – sintered 160 x 10-8

NdFeB – bonded 14,000 x 10-8

Ferrite 105

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Magnet Losses - Mitigation

Distribution of specific on-load PM losses

segmented

monolithic

P L

P mL n

Effect of segmentation on the magnet lossesm = transversal segmentsn = axial segments

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Efficiency maps (MTPA)

Imax = 325Arms, Twdg = 160C0, Tmag = 120C0

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Duty Cycle

Loss model of the typical racing car driving cycle for one lap

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Transient Thermal Analysis

Results for 20 laps drive cycle

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Experimental Data

Measured and calculated torque(q-axis current excitation, PMs at 40C0)

Measured total loss vs. current and speed at 40C0

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Carbon Nanotubes (CNT)

• Individual carbon nanotubes (CNT) can have a conductivity up to 100 MS/m and very low mass density

• Conductivity substantially decreases when individual CNTs are assembled to form macroscopic conductors

• Conductivity may be enhanced by plating nanotubes with copper (Cu).

Conductivity (MS/m)

Density (kg/m3)

Temp Coeff of Resistance (/K)

Thermal Conductivity (W/mK)

Specific Heat Capacity (J/kgK)

Copper 58.0 8960 0.0038 385 384

Aluminum 35.0 2700 0.0043 205 900

CNT Wire # 1 2.4 1500 0.0015 450 710

CNT Wire # 2 10.0 1500 0.0015 1230 710

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Fiber Development Laboratory at University of Kentucky (UK)

• Part of the large Center for Applied Energy Research (CAER).

• Largest solution spinning line found in an academic setting in North America.

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MWCNTs

Cu-plated MWCNTs

Bore dispersion

Alignment by drawing

Cu-MWCNT conductor core wire

Cu-plated Aligned MWCNT Wires

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Coreless Multi-Disc Axial Flux PM machine

• Systematic study on a suitable benchmark

• Coreless topology –windings account for most active weight and losses

• Conventional counterpart originally developed at University of Bath for the European HELINET solar airplane

• Multiple stator modules and rotor discs

• Stator with coils and a light supporting structure

• PM rotor.

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Example Design Studies

Performance improvement achieved by replacing copper coils with carbon nanotube (CNT) windings. Machines with CNT windings maybe larger in size and lighter. AC supplementary losses in NCT windings are negligible. Further improvements possible due to better heath transfer.

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US DOE Research Program for NCT Wires and Machines

High performance conductors to minimize losses in the stator windings

• To be demonstrated on a 28 AWG NCT round wire with 1 m length

• Minimum of 33% reduction in I2R losses per unit weight or volume over a 28 AWG round copper or Al wire at 1500C

• Use the new wire to demonstrate a 1 hp single phase induction motor, including windings with electric insulation.

Source: US DOE-FOA-0001467, Next Generation Electric Machines: Enabling Technologies, 2016.

Photo courtesy of Regal Beloit Corp.

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Conclusion

•Things that we can do today• Example ultra-high torque density (12Nm/kg) AIM motor developed

for Formula E racing cars• Innovate with existent materials• Automated design optimization• Motor performance under duty / driving cycles simulated using

electromagnetic and thermal coupled analysis

•Things that we maybe able to do in the future• New materials such as nanocarbon tubes and wires• It may take some time to deploy the new technology in conventional

industrial applications• First in line to benefit may be high-tech applications, such as those for

aerospace.

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References

• Wang, Yi, Ionel, D. M., Staton, D. A., “Ultrafast Steady-State Multiphysics Model for PM and Synchronous Reluctance Machines”, IEEE Transactions on Industry Applications, Vol. 51, No. 5, Sep/Oct 2015, pp. 3639-3646.

• Zhang Peng, Sizov, G. Y., Ionel, D. M., Demerdash, N.A.O., “Establishing the Relative Merits of Interior and Spoke-Type Permanent-Magnet Machines with Ferrite or NdFeB through Systematic Design Optimization”, IEEE Transactions on Industry Applications, Vol. 51, No. 4, Jul/Aug 2015, pp. 2940-2948.

• Wrobel, R., Simpson, N., Mellor, P., Goss, J., Staton, D. A., ”Design of a Brushless PM Starter-Generator for Low-Cost Manufacture and a High-Aspect-Ratio Mechanical Space Envelope“, Proceedings IEEE ECCE 2015 Congress, Montreal, Canada, Sept. 2015, pp. 813-820

• A. Fatemi, N. Demerdash, T. Nehl, D.M. Ionel, "Large-scale Design Optimization of PM Machines Over a Target Operating Cycle," in press, IEEE Transactions on Industry Applications, Early Access DOI: 10.1109/TIA.2016.2563383

• Yi Wang, D. M. Ionel, M. Jiang, S. J. Stretz, “Establishing the Relative Merits of Synchronous Reluctance and PM Assisted Technology Through Systematic Design Optimization”, in press, IEEE Transactions on Industry Applications, Early Access DOI: 10.1109/TIA.2016.2544831

• Popescu, M., Foley, I., Staton, D. A., Goss, J. E., “Multi-physics Analysis of a High Torque Density Motor for Electric Cars”, Proceedings IEEE ECCE 2015 Congress, Montreal, Canada, Sept. 2015, pp.6537-6544

• Fatemi A., Ionel D. M., Demerdash N.A.O., Popescu, M., “Design Optimization of Spoke-Type PM Motors for Formula E Racing Cars”, accepted for publication in Proc. of ECCE 2016

• Vandana Rallabandi, Narges Taran, D. M. Ionel and J. F. Eastham, “On the Feasibility of Carbon Nanotube Windings for Electrical Machines: Case Study for a Coreless Axial Flux Motor”, accepted for publication in Proc. of ECCE 2016.

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University of Kentucky – Solar Car

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Consortium and Acknowledgments

•The SPARK - SEMPEED Consortium was recently established to further the art of electric machine design

•Two academic sites at University of Kentucky and Marquette University and one partner software company, Motor Design Ltd (MDL)

•Four inaugural members: Grundfos, Kollmorgen, MTS, and Regal Beloit

• Inspired by the legacy of the SPEED Consortium

•The continued support of ANSYS for our academic research is gratefully acknowledged.

New Frontiers of Brushless PM Motor Technology - … · designed electric machines and drives with power ratings between ... and vector control ... New Frontiers of Brushless PM Motor

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