This document outlines an automatic procedure for designing and analyzing electric traction motors through multi-disciplinary analysis. It describes performing initial sizing and sensitivity analysis to explore different motor configurations. Key analyses include computing various loss mechanisms like AC proximity losses, investigating short circuits and demagnetization, verifying mechanical strength, and performing advanced thermal and vibration analyses. The goal is to optimize the motor design through this process to reduce losses, vibrations, and noise while ensuring adequate life, reliability, and performance.

1. Automatic procedure and detailed multi-disciplinary
analysis for an electric traction motor
UNIVERSITA’ degli Studi dell’AQUILA giovedì 17 maggio 2018

2. OUTLINE
REQUIREMENTS
REQUIREMENT SPECIFICATION

3. OUTLINE
REQUIREMENTS
PERFORMANCE
REQUIREMENTS
REQUIREMENT SPECIFICATION

4. OUTLINE
REQUIREMENTS
PERFORMANCE
REQUIREMENTS
LIFE &
RELIABILITY
REQUIREMENTS
REQUIREMENT SPECIFICATION

5. OUTLINE
REQUIREMENTS
PERFORMANCE
REQUIREMENTS
LIFE &
RELIABILITY
REQUIREMENTS
COST
REQUIREMENTS
REQUIREMENT SPECIFICATION

6. Initial Sizing

7. Compare Initial Results

8. Compare Initial Results

9. Focus on best configuration
perform sensitivity
analysis on geometry

10. Perform sensitivity analysis on geometry
Bridge & web thickness variation
Magnetpropertiesvariation

11. From initial sizing to detailed analysis
• Explore various losses
computation methodology in Flux
 AC proximity and skin effect losses
 Iron losses
 Magnet losses due to eddy current
 Effect of PWM on losses
Investigate short circuit and
demagnetization

12. From initial sizing to detailed analysis
• Explore various losses
computation methodology in Flux
 AC proximity and skin effect losses
 Iron losses
 Magnet losses due to eddy current
 Effect of PWM on losses
Investigate short circuit and
demagnetization
Verify the strength of
mechanical parts with
OptiStruct
Verify the thermal behaviour and
estimate actual heat exchange
coefficients

13. AC losses due to proximity and skin effect
Automated process of
generating solid conductors
and associated components
in the circuit

14. AC losses due to proximity and skin effect
135 mech deg 135 mech deg
Conductors in a bundle
are NOT TWISTED
Conductors in a
bundle are TWISTED
 MAX Current density: 36.8 A/mm²
 Total copper loss: 1110 W
• MAX Current density: 14 A/mm²
• Total copper loss: 422 W

15. Magnet losses

16. Iron losses
    2/3
me
2
m
2
22
mhTOT f.Bkf.B
6
d
fBkdP 


Bertotti Model
With
◦Kh : hysteresis coefficient
◦σ : conductivity
◦d : thickness
◦Ke : excess losses
◦f : frequency
◦Stacking factor
Ke and Kh can be extracted
from iron losses versus
frequency and flux density
There is an Excel file with a
procedure allowing extracting more
easily, Kh and Ke

17. Iron losses
Loss Surface Model
 Based on specific measurements for each grade
 Measurement includes variation versus B but also versus dB/dt
 Accounts also for harmonics
 Developed by G2ELAB research team

18. Impact of PWM on losses
S1 without PWM
[rpm] ElMag torque [N∙m]
ElMag power
[kW]
Rotor iron losses
[W]
Stator teeth iron losses
[W]
Stator yoke iron losses
[W]
Iron losses
[W]
17000 59.37 105.70 546.42 3772.24 781.63 5100.29
S1 with PWM (switching frequency 10 kHz)
[rpm] ElMag torque [N∙m]
ElMag power
[kW]
Rotor iron losses
[W]
Stator teeth iron losses
[W]
Stator yoke iron losses
[W]
Iron losses
[W]
17000 59.58 106.07 495.82 3692.43 969.85 5158.09
S1 with PWM (switching frequency 20 kHz)
[rpm] ElMag torque [N∙m]
ElMag power
[kW]
Rotor iron losses
[W]
Stator teeth iron losses
[W]
Stator yoke iron losses
[W]
Iron losses
[W]
17000 59.34 105.63 806.06 4262.78 1015.00 6083.84

19. Short Circuit and Demagnetization
Transient Short-Circuit during steady-state
motor operation at maximum load
Demagnetization Effect

20. Short Circuit and Demagnetization
Transient Short-Circuit during steady-state
motor operation at maximum load
Steady-state effect on current and
torque

21. Thermal Analysis

22. Electric – Thermal Loop

23. Advanced Thermal Analysis
Geometry of the water
jacket should be carefully
selected and designed.
Bad design of water-jacket
cooling can lead to poor
thermal performance and
reduce the useful power of
the motor.

24. Advanced Thermal Analysis
Spiral ducts vs axial ducts may lead to different performance, depending
on many geometrical factors such as position and shape of the pipes.

25. Advanced Thermal Analysis
The actual heat
exchange coefficient due
to convection might be
unevenly distributed
across the outer surfaces
of the motor, leading to
critical hotspots and to
reduced reliability.
Optimal forced ventilation
is the result of the proper
design of the complete
system: fan + cowlings,
shrouds, grids, fins …

26. Strength verification of rotor
Rotor shape greatly affect performance both
in terms of delivered power and reliability

27. Strength verification of rotor
Rotor shape greatly affect performance both in terms of delivered power and reliability
Good electrical performance
Poor mechanical performance

28. Strength verification of rotor
Rotor shape greatly affect performance both in terms of delivered power and reliability
Poor electrical performance
Good mechanical performance

29. Strength verification of rotor
Good compromise
Rotor shape greatly affect performance both in terms of delivered power and reliability

30. Vibration and Noise

31. Vibration and Noise
The process of optimization may be repeated
in order to reduce vibration and noise

32. Optimization results
Reduction: 94.2%
Reduction: 83.6%

33. CONCLUSION
The final motor runs as expected on the test bench and it
is ready for the next stage on the car.