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Technology Roadmap for

Large Electrical Machines

Joe Beno, Ph.D.

j.beno@cem.utexas.edu

(512) 924-2241

Kiruba Haran, Ph.D.

kharan@illinois.edu

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Grainger CEME/IEEE WorkshopTechnology Roadmap for Large Electrical Machines

April 5 – 6, 2016, University of Illinois at Urbana-Champaign

Industry Academia Government

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Why?

Aviation

NASA

Offshore Wind

SIEMENS

Oil & Gas

GE

Ship propulsion

GE

High Speed Rail

ABB

Defense

AFRL

Financial Tribune

Tidal

ABB

Mining

A number of emerging applications can be significantly transformed by new electric machines and drives technology.

Significant progress being made in enabling technologies: new materials, power electronics, manufacturing techniques, etc.

Key stakeholders can benefit from expert opinion on projected technology advances in the next decade or so.

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2016 Grainger CEME/IEEE Workshop:Technology Roadmap for Large Electrical Machines

Workshop goal:

Draft a consensus-based technology roadmap with a 5 – 10 year time frame for large (1-10MW) electrical machines (that convert electrical energy to mechanical, and vice-versa) and required auxiliaries.

Six ‘working groups’ on sub-topics:

▪ Advanced Non-Cryo Machines: Chair - Joe Beno, UT-CEM

▪ Superconducting Machines: Chair - Haran Karmaker, TECO-Westinghouse

▪ Enabling Materials: Chair - Tim Haugan, AFRL

▪ Modeling Tools: Chair - Scott Sudhoff, Purdue

▪ Power Electronics: Chair - Ian Brown, Illinois Institute of Technology

▪ System Integration: Chair - Dave Torrey, General Electric

Recommendations:

▪ Meet periodically at relevant conferences to update roadmap (e.g. next EnergyTech?)

▪ Share results broadly through publications in trade journals

▪ Engage AIAA and IEEE on collaborative events – symposiums, webinars

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Status

Roadmaps:

• Advanced Non-Cryo MachinesRoadmap document still being worked, needs additional inputs. Some aspects being submitted for publication in IET Special Issue on High Speed Machines

• Superconducting MachinesRoadmap being published in IOP SUST

Collaboration:

• The workshop reinforced the need to bring together electrical engineers and aerospace experts as the industry looks to more electric propulsion technologies.

• The AIAA (led by the Aircraft Electric Propulsion Working Group - Marty Bradley, Chair) and IEEE (led by the Transportation Electrification Community - Yaobin Chen, Chair) are discussing an MOU for a two-day symposium that will focus on electric aircraft technology, in July 2018.

Education:

• Exploring co-sponsored tutorials and webinars by AIAA & IEEE (+ INCOSE?)

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SC Machines – Working Group

▪ Tabea Arndt, Siemens Corporate Technology, Germany

▪ Haran Karmaker, TECO-Westinghouse Motor Company, USA

▪ Kiruba S. Haran,University of Illinois at Urbana-Champaign, USA

▪ Swarn Kalsi, Kalsi Green Power Systems, USA

▪ Rod Badcock, Victoria University of Wellington, New Zealand

▪ Bob Buckley, Victoria University of Wellington, New Zealand

▪ Timothy Haugan, The Air Force Research Laboratory, Wright-Patterson AFB,

USA

▪ Mitsuru Izumi, Tokyo University of Marine Science and Technology, Japan

▪ David Loder, Rolls-Royce North American Technologies, Inc.—Liberty Works,

USA

▪ James W. Bray, General Electric - Global Research Center, USA

▪ Philippe Masson, University of Houston, USA

▪ Ernst Wolfgang Stautner, General Electric - Global Research Center, USA

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SC Machines Roadmap Summary

Projection

A. Fully superconducting machines have the potential to attain the highest efficiency by minimizing losses in both the field and armature windings. To attain this, significant advances in ac-capable superconductors must be made. To obtain superior efficiency, the ac losses in a superconducting armature must be less than 0.1% of the machine rating. This has to be achieved within “ac” flux on the order of 103

Tesla/second to be competitive in power density with the partially superconducting machines.

B. Partially superconducting machines also have potential forincreased specific power, with complete elimination offerromagnetic components and higher operating flux density.For the full entitlement of these topologies to be realized,HTS conductors capable of high fields at high temperaturesneed to be matured and composite structures developed toreplace relatively heavy vacuum vessels and torque tubes.

C. Machines with bulk superconductors is another area ofactive research, though they are currently at a lowertechnology readiness level. Improved bulk superconductorscapable of operation at liquid nitrogen temperatures andways to magnetize the bulks at high fields would furtherincrease the potential for these machine types.

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SC Machines - recommendations

For the promised benefits of superconducting machines to be

achieved, further progress must be made in:

• Unit length of HTS conductors (500m+)

• Mechanical properties of the conductors

• Critical current at high temperatures and magnetic fields

• Supporting materials (insulation, mechanical support)

• Composite structures

• Quench detection and control

• High current brushes

• Light weight cryostats

• Dedicated cooling technology/coolers adopted to cooling power needs

• Specific cost ($/kAm) at operating point (temperature and magnetic field)

• AC loss reduction

• Description of system level “value add”

• Awareness and training of engineers in conventional technologies

• Creating an “economy of scale” effect by (small, but steady) market demands

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Grainger CEME/IEEE Workshops onTechnology Roadmap for Large Electrical Machines

Advanced Machine category, focused on MW Class

Electrical Machines including cryo-cooled machines

but not including Superconducting Machines.

Amrhein, Marco, PC Krause and Associates

Beno, Joe, University of Texas, CEM

Bortoni, Edson, UNIFEI

Bowman, Cheryl, NASA

Filipenko, Mykhaylo, Siemens

Hull, John , Boeing

Huynh, Phuc, University of Illinois

Klontz, Keith, Advanced Motor Tech

Knight, Andy, University of Calgary

Krien, Phil, University of Illinois, Urbana-

Champaign

Madavan, Nateri, NASA

Rico, Raul, Siemens Rong, Charles, U.S. Army

Research Laboratory

Saban, Dan, Meggit

Sanchez, Reed, University of Illinois

Sarlioglu, Bulent, University of Madison

Shah, Manoj, GE Global Research

Tangudu, Jagadeesh K, United Technologies

Torrey, Dave, General Electric

Wu, Thomas, University of Central Florida

Yi, Melody, University of Illinois

Yoon, Andy, University of Illinois

Zhang , Xiaolong, University of Illinois

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Some Conventional Metrics

Specific Power (W/kg)

Power Density (W/m^3)

Specific Energy (MJ/kg)

Energy Density (MJ/m^3)

Torque Per Unit Rotor Volume (TRV, N-m/m^3)

Involve Speed

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Focus Applications

Many variations for machine design and machine topologies – Common for machine design to be uniquely optimized for particular applications.

Advanced Machines focused on small number of high pay-off applications:

• Aircraft Propulsion Electrification – generally employing distributed electric propulsor motors and a smaller number of turbine driven generators

• Stand-Alone Micro-Grids that are sufficiently large to benefit from MW class electric machines

• Renewable Energy Generation that interfaces with large utility grids, generally wind generation.

Focus applications considered as high pay-off because they:

• Have a high pay-off for society

• Represent unique opportunities at this time in our nation’s history

• Also have large benefit to other applications

• Are synergistic with each other (e.g., large commercial electric aircraft are micro-grids with unique challenges)

• Have a high level of funding support.

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Most Relevant Transmission Systems

Aircraft Propulsion Electrification:

• Often powered by high-speed turbo-generators feeding variable voltage dc bus, fixed frequency ac bus, or variable frequency ac bus

• ac bus frequencies often fixed by the gas-turbine, possibly with a fixed reduction.

Stand-Alone Micro-Grids (e.g., electric ship, hybrid electric combat vehicles with pulse weapons):

• Often powered by high-speed turbo-generator or diesel generator feeding a variable voltage dc bus, fixed frequency ac bus, or variable frequency ac bus

• Load requirements often determine type of bus.

Renewable Energy Generation:

• Interfaces with large utility grids

• Bus operates at a fixed frequency, fixed voltage, stiff, highly regulated grid.

Machine types for focus applications often depend on type of power transmission system.

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Considerations for Optimization of Machine Size, Mass and Efficiency

Basic physics of rotating electrical machines that impact size/mass:

• Power equals torque times rotational speed: P = w Torque

• Torque is function of the air gap magnetic radial and circumferential fields produced by the

rotor and stator (Br and Bq );

Torque = radiusairgap ∮s (Bq Br / mo ) 𝐝𝐚

= radiusairgap (lengthrotor * 2 * pi * radiusairgap) < Bq Br >airgap / mo

= 2 Volumerotor < Bq Br >airgap / mo where < > denotes average value

• Airgap fields:

➢ limited by motor material properties

➢ limited to ~ 0.5 to 1.5 Tesla for traditional iron-core machines.

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Considerations for Optimization of Machine Size, Mass and Efficiency (cont)

Torque = 2 Volumerotor < Bq Br > / m o

Bairgap limited by material properties in the motor

• Torque per unit Rotor Volume (TRV) is often used figure of

merit for evaluating machine size

• Stator surrounds the rotor, adding to the overall machine volume

and mass

• To maximize TRV: Maximize flux density in airgap and minimize

space dedicated to other components (e.g., windings). Large

machines win because they have:

➢ Enough space to accommodate liquid cooling to operate at

higher current densities and reduce space devoted to

windings

➢ Enough surface area to accommodate high pole count and

reduce backiron thickness

Motor TypeTRV

(kN-m/m^3)

Fractional horsepower, totally

enclosed, fan cooled industrial motors 1.4 – 4

Integral horsepower totally

enclosed, fan cooled industrial motors 15 – 30

High-performance servos 20 – 45

Aerospace machines 45 – 75

Very large Liquid cooled machines 130 – 220

Typical TRVs

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Considerations for Optimization of Machine Size, Mass and Efficiency (cont)

TRV Comments and Consequences:

• Minimum required rotor volume of electric machine is effectively determined by the required machine

torque and material properties.

➢ True for all rotating electromagnetic devices, including motors, generators, and magnetic gears.

• For generators, focused on a specified output power, rotor volume and therefore overall generator

volume can usually be reduced if the input shaft speed can be increased which serves to decrease the

required operational torque (P = t w).

• Motors often have specified power and specified output shaft speed, which defines required output

torque.

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• Mass fractions are consistent over a wide range of motor types and power.

• Casing is the largest single element in all motors. (~40%)

• Stator Laminations are second (~30%)

• Rotor + shaft are third (~20%)

• Neither the windings (10%) nor the magnets (2%) are major contributors to mass

Motivation: Look at SystemMass Reduction Opportunities

Item kg % of Total

Casing 14.1 38.3%

Stator Laminations 10.36 28.1%

Rotor + Shaft 6.7 18.2%

Windings 4.93 13.4%

Magnets 0.77 2.1%

Total 36.86

Prius Motor Mass Distribution

Item grams % of Total

Casing (stator, fan, front and back plates) 692 35.4%

Stator Laminations 664 34.0%

Rotor + Shaft 438 22.4%

Windings 160 8.2%

Total 1954

1/20 hp Shaded Pole - General Categories

Item kg % of Total

Casing (stator, fan, front and back plates) 12.715 43.7%

Stator Laminations 7.518 25.9%

Rotor + Shaft 6.6 22.7%

Windings 2.242 7.7%

Total 29.075

3 hp 3-Phase - General Categories

Subsystem/Component Mass at Motor/Generator Level

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Motivation: Look at System Mass Reduction Opportunities (cont)

Opportunities for Mass Reduction at Motor/Generator Level

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Enabling Materials

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Aircraft Propulsion Electrification

(generally employing distributed electric propulsor motors and

a smaller number of turbine driven generators)

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Distributed Aircraft Propulsion

Majority of large jet-powered transport aircraft have thrust-generating

engines under the wings or on the fuselage to minimize aerodynamic

interactions on the vehicle operation.

Advances in computational and experimental tools and new technologies in

materials, structures, and aircraft controls, etc. enable a high degree of

integration of the airframe and propulsion.

Distributed propulsion fully integrates the propulsion system within an

airframe to take exploit the coupling of airframe aerodynamics and

propulsion thrust stream by distributing thrust using many propulsors on

the airframe.

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Distributed Aircraft Propulsion

Benefits

• Improvement in aircraft performance, noise reduction to the surrounding community, and/or

providing the capability of Short Take Off Landing (STOL).

• Reduction in fuel consumption by ingesting the thick boundary layer flow and filling in the

wake generated by the airframe with the distributed engine thrust stream.

• Spanwise high lift via high-aspect-ratio trailing-edge nozzles for vectored thrust providing

powered lift, boundary layer control, and/or supercirculation around the wing, all of which

enable short take-off capability.

• Better integration of the propulsion system with the airframe for reduction in noise to the

surrounding community through airframe shielding.

• Reduction in aircraft propulsion installation weight through inlet/nozzle/wing structure

integration.

• Elimination of aircraft control surfaces through differential and vectoring thrust for pitch,

roll, and yaw moments.

• High production rates and easy replacement of engines or propulsors that are small and

light.

• For the multi-fan/single engine core concept, the propulsion configuration provides a very

high bypass ratio enabling low fuel burn, emissions, and noise to surrounding communities.

Hyun Dae Kim (NASA GRC), Distributed Propulsion Vehicles, 27th International Congress of the Aeronautical Vehicles, 2010

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Projected Timeframe to Tech Readiness Level 6

5 to 10

MW

• Hybrid electric 50 PAX regional

• Turboelectric distributed propulsion 100 PAX regional

• All-electric, full-range general aviation

• Hybrid electric 100 PAX regional

• Turboelectric distributed propulsion 150 PAX

• All electric 50 PAX regional (500 mile range)

• Hybrid electric 150 PAX

• Turboelectric 150 PAX

>10 MW

Po

wer

Le

ve

l fo

r E

lec

tric

al P

rop

uls

ion

Today 10 Year 20 Year 30 Year 40 Year

• Turbo/hybrid electric

distributed propulsion

300 PAX

• All-electric and hybrid-electric

general aviation (limited range)

Technologies benefit more electric and

all-electric aircraft architectures:

• High-power density electric motors

replacing hydraulic actuation

• Electrical component and

transmission system weight

reduction

kW class

1 to 2

MW class

2 to 5

MW class

Superconducting

Machines

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Electric Machine Related TechnologiesThat Enable/Accelerate Turbo-Electric and Hybrid Aircraft

• Electric Machine Topologies:– Higher efficiency designs: reduce the losses in the motor

through better topologies without sacrificing power density

– Ironless or low magnetic loss

– Concepts which allow motor to be integrated into the existing

rotating machinery (shared structure)

– Concepts which decouple motor speed and compressor speed

• Electric Machine Components and Materials– Flux diverters or shielding to reduce AC loss or increase

performance

– Composite support structures

– Improvements in superconducting wire: especially wire

systems designed for lower AC losses

– Rotating Cryogenic seals

– Bearings: cold ball bearings, active & passive magnetic

bearings; hydrostatic or hydrodynamic or foil for systems w/ a

pressurized LH2 source

– Flight qualification of new components

• Cryocoolers– Flight weight systems for superconducting and cryogenic

machines, converters and transmission lines

Vehicle and thermal management

concepts need to be defined

alongside propulsion systems to

assure that the full system is

lightweight and thermally balanced.

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Stand-Alone Micro-Grids

(that are sufficiently large to benefit from MW class electric machines)

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Advanced Machines for General Purpose Microgrids

Connected to 60 Hz terrestrial power grid but with islanding capability, or to provide an extension or smaller scale reproduction of the same terrestrial grid in isolated areas or in emergency situations.

• These microgrids will probably dominate commercial sector in for 10-15 years

• Mostly of the conventional 3600 RPM machine types driven by cost.

• Unlikely that the commercial suppliers of these microgrids will embark on an extensive R&D effort.

Exceptions:

➢ Mobile applications (e.g. quick response unit for disaster relief)

➢ Non-permanent reconfigurable installations (e.g. forward operating bases).

Current state of the art in commercially viable portable megawatt scale power generation systems:

• Skid or trailer mounted gas turbines driving generators at 1,800 or 3,600 rpm through a speed reducing gearbox to provide 60 Hz output

• Typically designed for industrial applications

• 3 MW system weighs on the order of 65,000 lbs, transported overland by tractor trailer.

• Technology development most likely to take place in this area is in modular, MW-scale portable power systems capable of flexible customization and rapid transport

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Technology Roadmap As Seen By the US Navy

Primary Microgrids of Interest:

Variable frequency including DC

and variable voltage

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Some State of the Art Considerations for Improving Performance of Microgrid Machines

• High tip speeds, high frequency, high shaft speeds: ~ 300 m/s; > 300 m/s may require vacuum

• Allowable stress/strain limits: Inconel, Titanium and a high performance Toray T1000G graphite composite

• Operating temperature limits: typically ~ 220 C

• Slot current density: typically 5 MA/m^2 advanced state of the art for the ac armature winding slot current density. For dc field windings, a value closer to 8 MA/m^2

• Soft magnetic materials: M19, M43 Hiperco

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Projections From Commercial Designs of Size Reduction for 25 MW Generators

• Text

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Roadmap for Advanced Machines for Microgrids for the Next 10 – 15 Years

Roadmap for advanced machine development for stand-alone microgrids should include the following general tasks

• Demonstration of reliable, multi-phase, MW level machines at frequencies higher than 200 Hz

• Demonstration of a composite enclosure machine performance

• Demonstration of a cost effective, reliable liquid cooled windings in both stator and rotor

• Demonstration of new concepts for noise abatement

• Material development:

➢ higher strength composite filaments for banding

➢ insulation systems rated for operation above 220 C

➢ soft magnetic materials with improved magnetic, mechanical, chemical properties

➢ hard magnetic materials with better performance and less dependent on strategic elements

• Development of a generator designed with the HIA topology with power density comparable to that of wound rotor or permanent magnet machines

• Study the potential system advantage of using doubly-fed machines and their attendant converters in a microgrid application.

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Renewable Energy Generation

(that interfaces with large utility grids, generally wind generation)

Under development : Dave Torrey, GE Global Research

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Upcoming Events

IEEE and AIAA Electrification of Aircraft Transportation

Symposium, Summer 2018, Cleveland

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STOP