The only international event focusing exclusively

on all aspects of e-motor technologies

Dear E-Motor Expert,

Today we are pleased to share with you a presentation by one of our speakers from last year’s

Advanced E-Motor Technology Conference:

Dr. Alex Michaelides, Technical Specialist - Electrical Machines and Power Electronics at Jaguar

Land Rover in cooperation with James Widmer and Mohammad Kimiabeigi from University of

Newcastle.

We hope you enjoy this presentation:

Low Cost, High

Performance

eMotors for Traction

Applications

Alex Michaelides – Jaguar LandRover

James Widmer - University of Newcastle

Mohammad Kimiabeigi - University of Newcastle

Acknowledging the

involvement of:

Content

• Traction Motor Cost Drivers

– Alex Michaelides

• Example: High Power Density Ferrite Machine

– James Widmer

• Conclusions

Rare Earth Magnet Costs

31

42

158

0

50

100

150

200

250

300

Interior Permanent Magnet Motor

GB

P(£

) NdFeB

Copper

Steel

68%

Materials Cost 80kW Traction Motor(NdFeB - $120/kg)

eMachine magnet

weight/cost minimization• Approaches to reducing weight or cost of permanent magnets:

- Use of embedded rotor topologies (gain reluctance torque)

- Permanent Magnet Assisted Synchronous motor

- Adding term

- Embedded magnet designs generally increase winding

inductance

- Reduce rotor temperature

- … and hence use a lower magnet grade

- Use Ferrite Magnet Technology

- Use of non PMSM technologies :

- Induction, wound rotor, switched reluctance motors.

dqd ILL

Rare Earth Magnet Alternatives

Reduced

Rare Earth

BMW i3

Induction

Motor

TESLA

Other Magnets

(Ferrite)

See Example…

Synchronous

Reluctance

Not yet…

Switched

Reluctance

Land Rover

Defender

Wound Rotor

Continental

/ Renault

Moving away from PMSMs: example SRM

Higher Speed Electrical Machines

• Faster motor, smaller

motor for same power

– BEV Traction motors today

operate at around 10krpm

– Proportional reduction in

mass (cost) as speed

increases

P = 𝑇𝜔𝑇 ∝ 𝑅𝑜𝑡𝑜𝑟 𝑉𝑜𝑙𝑢𝑚𝑒

0

5

10

15

20

25

30

35

40

0 10000 20000 30000 40000 50000

Idea

listi

c A

ctiv

e M

ass

for

80kW

(kg

)

Motor Rated Speed (rpm)

SR Operation at Higher Speed

SR Motor lends itself to operation at higher speeds:

– No magnet or copper losses

– More robust mechanical design

– Excellent efficiency

0

100

200

300

0 2000 4000 6000 8000 10000 12000

To

rqu

e

Speed

SRM Max η

eMotor Torque (reluctance and

magnet torque)

In embedded PMSMs the resulting

motor torque is divided into:

‘Excitation torque’: The interaction

of permanent magnet and stator

current B-fields. This torque

component is proportional to the

motor current (if no saturation).

Reluctance torque: ‘Alignment

torque’ arising from the difference in

d and q axis reluctance values. This

component is proportional to the

square of motor current (if no

saturation).

dqd ILL

‘Synchronous

Reluctance’ Rotor

• ‘Synchronous reluctance’ rotor

adds significant reluctance torque

component

• Addressing ‘ferrite-magnet’ variant

challenges

• Low remanence

Magnet content

Rotor topology

• Low coercivity

Rotor topology

Pole count

Torque Characteristic in SyncR rotor

with Ferrite and NdFB Magnets

• Torque-speed performance of 8-pole PMaSyncR design

with Ferrite (Left) and NdFeB (Right) magnets

High Performance Ferrite

Traction Motor

Ferrite Magnet Based Motor

Why?

• Standard, 3phase Inverter

• Low cost magnets

• Low rotor losses (no rotor

windings)

Other cost reduction measures:

• Higher Speed (15krpm)

• Aluminium windingsMaterial Cost per kg

NdFeB $120

Ferrite ~$10

0

0.2

0.4

0.6

0.8

1

1.2

1.4

-1000 -800 -600 -400 -200 0

Flu

x D

ensi

ty (

B)

Magnetising Field Strength (KA/m)

Ferrite

NdFeB

Problem: Weak Magnets

• Remnance:

– Ferrite 0.4T

– NdFeB 1.2T

– T ∝ B

• Solutions =>

• NB: Need for

distributed winding

Q

Reluctance Torque:

PMA-SynRM

Flux Concentration:

Spoke Type Motor

Problem: Weak Magnets

• Coercivity:

– Ferrite 400kA/m

– NdFeB 900kA/m

– Demagnetisation

• Short circuit

Red A

reas D

em

agnetis

ed

Electrical Machine –

Conductors• Eliminate Copper

• £4.10 / kg [1], 10kg for 80kW machine

• Use Aluminium for Motor Windings

• £1.25 / kg [1]

• Mass is half that of copper for same conductivity => 5kg for

80kW machine

[1] London Metal Exchange, 9th Dec 2014

Aluminium Windings –

Challenges and Solutions

Low Conductivity

=> High fill factor / larger slots

High Thermal Expansion

=> Careful mechanical design

Aluminium Conductor Termination

=> Use of appropriate methods

Aluminium Windings

85% Net Fill Factor

For Single Tooth Windings: For Distributed Windings: Denso 3

0kW

Tra

ctio

n M

oto

r

DC Winding Loss => increase fill

factor as far as possible

AC Winding Loss=> <2/3 of Copper

High Speed Traction Motors –

Challenges and Solutions

Rotor Stress and Fatigue Life

=> Materials / mechanical design optimisation

Bearings

=> Lubrication, careful design optimisation

High Electrical Frequency, Iron and AC Losses

=> Thin electrical steels, winding optimisation

Higher Speed Electrical Machines

• Faster motor, smaller

motor for same power

– BEV Traction motors today

operate at around 10krpm

– Proportional reduction in

mass (cost) as speed

increases

P = 𝑇𝜔𝑇 ∝ 𝑅𝑜𝑡𝑜𝑟 𝑉𝑜𝑙𝑢𝑚𝑒

0

5

10

15

20

25

30

35

40

0 10000 20000 30000 40000 50000

Idea

listi

c A

ctiv

e M

ass

for

80kW

(kg

)

Motor Rated Speed (rpm)

Higher Speeds

Ferrite

MagnetElectrical

Steel

Non-Magnetic

Support

Slot Wedge

Support

Electrical

Steel

Multiphysics Optimisation

- Electromagnetic

- Structural

Higher Speeds

Segmented RotorSingle Piece Rotor

Electrical steel rotor

Validation Testing

Ferrite vs NdFeB

Volume:• NdFeB IPM motor (blue)• Ferrite motor (grey)

Peak

Continuous

NdFeB

Conclusions

• Traction Motor cost reduced by:

– Replacing Rare Earth Magnets with Ferrite

– Replacing Copper with Aluminium windings

– Increase speed from 10krpm to 15krpm

– Material cost saving ~50%

– Also low mass, lower AC losses, ease of recycling

• Less than the theoretical maximum cost saving

– Ferrite magnets

– High speed structure not electromagnetically optimum

Dear E-Motor Expert,

The 4th International Conference on Advanced E-Motor Technology 2016 will give a profound

insight into global market trends of e-motor materials to reduce costs and optimize the production

process. Meet your peers to discuss the latest e-motor design and the move towards 48 Volt

systems. Furthermore during this two-day event we will discuss case study insights by the leading

OEM’s and technology solution providers.

Our conference will bring together experts from along the value chain to ensure maximum

knowledge transfer, professional exchange and networking opportunities. For more information

and the schedule of events, please download the agenda. If you have any questions, please email

at eq@ipc.de or call +49 (0) 30 20 913 - 274

We look forward to meeting you in February 2016 in Berlin!

Kind regards,

Automotive IQ / A Division of