For today’s efforts to drive eMotor Innovation, the reduction of cost and weight of permanent magnets is essential! But what are the options? Is moving away from the Permanent Magnet Synchronous Motor the right thing to do? Dr. Alex Michaelides, Technical Specialist - Electrical Machines and Power Electronics at Jaguar Land Rover discusses these questions in the presentation here: http://bit.ly/Presentation-Michaelides

1. The only international event focusing exclusively
on all aspects of e-motor technologies

2. 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:

3. 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:

4. Content
• Traction Motor Cost Drivers
– Alex Michaelides
• Example: High Power Density Ferrite Machine
– James Widmer
• Conclusions

5. Rare Earth Magnet Costs
31
42
158
0
50
100
150
200
250
300
Interior Permanent Magnet Motor
GBP(£)
NdFeB
Copper
Steel
68%
Materials Cost 80kW Traction Motor
(NdFeB - $120/kg)

6. 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 

7. 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

8. Moving away from PMSMs: example SRM

9. 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 = 𝑇𝜔
𝑇 ∝ 𝑅𝑜𝑡𝑜𝑟 𝑉𝑜𝑙𝑢𝑚𝑒
0
5
10
15
20
25
30
35
40
0 10000 20000 30000 40000 50000
IdealisticActiveMassfor80kW(kg)
Motor Rated Speed (rpm)

10. 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
Torque
Speed
SRM Max η

11. 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 

12. ‘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

13. 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

14. High Performance Ferrite
Traction Motor

15. 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 windings
Material 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
FluxDensity(B)
Magnetising Field Strength (KA/m)
Ferrite
NdFeB

16. 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

17. Problem: Weak Magnets
• Coercivity:
– Ferrite 400kA/m
– NdFeB 900kA/m
– Demagnetisation
• Short circuit
RedAreasDemagnetised

18. 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

19. 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

20. Aluminium Windings
85% Net Fill Factor
For Single Tooth Windings: For Distributed Windings:
Denso30kWTractionMotor
DC Winding Loss => increase fill
factor as far as possible
AC Winding Loss=> <2/3 of Copper

21. 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

22. 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 = 𝑇𝜔
𝑇 ∝ 𝑅𝑜𝑡𝑜𝑟 𝑉𝑜𝑙𝑢𝑚𝑒
0
5
10
15
20
25
30
35
40
0 10000 20000 30000 40000 50000
IdealisticActiveMassfor80kW(kg)
Motor Rated Speed (rpm)

23. Higher Speeds
Ferrite
MagnetElectrical
Steel
Non-Magnetic
Support
Slot Wedge
Support
Electrical
Steel
Multiphysics Optimisation
- Electromagnetic
- Structural

24. Higher Speeds
Segmented RotorSingle Piece Rotor
Electrical steel rotor

25. Validation Testing

26. Ferrite vs NdFeB
Volume:
• NdFeB IPM motor (blue)
• Ferrite motor (grey)
Peak
Continuous
NdFeB

27. 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

28. 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