Electric Machine Design for Automotive Applications

Dr David Staton

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Topics

Automotive Electrical Traction – Fast Drive Cycle Analysis

Automotive Traction Motor Design Example

Summary

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Automotive Electrical Traction

Range of configurations under development Mild, Series, Parallel and Plugin Hybrid

Battery Electric and Range Extender

Main design drivers:Efficiency

Power Density

Cost

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Many Possible Motor Design Configurations

Many choices to be made when designing a motor:BPM, Induction, Synchronous Reluctance, SRM ….

Design Variables Slots/poles, Magnet Type, IPM design, Dimensions ……

Winding Type Distributed, Tooth Wound, Bar/Hairpin, Litz, Cu/Al …..

Cooling Type Air, Water Jacket, Rotor Fluid, Slot Oil, Oil Spray ……

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Dynamic Operation The operation of these machines is very dynamic and consideration of

performance across the full torque/speed operating envelope is required

Modelling tools need to support this

In order to optimize the motor design for particular drive cycles we need a fast way to analyze the motors electromagnetic and thermal performance on the required duty cycle load

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Key Features to Enable Fast Drive Cycle Analysis

Calculation of the efficiency map using: Fast electromagnetic calculation

Minimum number of electromagnetic calculations

Accurate but fast loss calculations including complex losses like magnet loss (with segmentation) and proximity losses

Automatic calculation of drive control strategy (maximum torque/amp)

Calculation of the drive cycle thermal transient using a lumped circuit solver: Losses from the efficiency map

Losses scaled with temperature

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Motor-CAD for Fast Duty Cycle Analysis

Motor-CAD EMag, Therm and Lab modules developed to enable fast drive cycle/duty cycle analysis in an integrated software

EMag: calculate flux-linkage & loss data with minimum 2D FEA solutions

Lab: Use FEA data to calculate & plot efficiency & loss maps. Then define duty cycle torque & speed vs time and calculate loss vs time data from loss maps

Therm: Pass loss v time data to lumped circuit thermal model for thermal transient calculation

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Product Development Workflow Workflow much larger topic area than detailed motor design

Motor-CAD useful for all areas of the workflow and not just detailed design

Motor-CAD used by both motor designers and application/system/test engineers

Automated links to other software (ANSYS Mechanical, Matlab Simulink, Optimisation) useful to speed up the workflow

Motor Design Engineer

Motor Type & Topology + Initial Sizing Model Calibration

Reduced Order Models & Flux Linkage/Loss Maps

Design Optimisation & Drive Cycle Analysis

System Engineer

Application Engineer

Test & Design

Engineer

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Manufacturing Data Built into ModelsMany manufacturing uncertainties that affect temperature rise: Goodness of effective interface between stator and housing How well the winding is impregnated or potted Leakage of air from open fin channel blown over machines Cooling of the internal parts in a TENV and TEFC machine Heat transfer through the bearings etc.

Test program over 18 years developing data to quantify such issues: Set default parameters in Motor-CAD giving good level of accuracy without the user having done extensive

calibration using testing of their own machines

Also automated choice of model type to give high accuracy

Example of assistance given to set stator lamination to housing interface thermal resistance

Interface resistance and conductance data that is suitable for thermal experts

Equivalent interface gap that is useful to non heat transfer specialist as easy to visualise

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Automotive Traction Motor Design Examples

A selection of published design examples for automotive traction motors are given next

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Toyota PRIUS Efficiency Map Validation

Measured Efficiency MapMotor-LAB Calculation

Validation based on Toyota 2004 Prius test data from ORNL published at PEMD 2012

Excellent match measured and calculated efficiency map

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Performance Prediction for Tesla Model S Motor Data from teardown analysis of the Tesla Model S electric motor

Copper rotor induction motor with potted end windings and water cooled stator and rotor

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Evoque_e / Concept_e Innovate UK Project MDL project member with JLR to develop for 3 demonstrators:

MHEV (Range Rover Evoque):

Mild Hybrid with 48V lithium ion battery pack

15 kW crank integrated motor with disconnect clutch

sandwiched between the prototype diesel engine (90 PS) and 9 speed transmission

PHEV (Range Rover Sport):

Plug-In Hybrid with prototype petrol engine (300 PS) and 8 speed transmission

longitudinally mounted within a Range Rover Sport

150kW electric motor

320-volt lithium ion battery packaged in the boot

BEV (Range Rover Evoque):

Bespoke research demonstrator based on JLR aluminium vehicle architecture

Modified underbody to mount the 70 kWh HV lithium ion traction battery and electric axle drive (EAD) units

Front drive unit with single speed transmission coupled with an 85 kW electric motor

Rear drive unit features a twin speed transmission coupled with a 145 kW electric motor

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Evoque_e / Concept_e BEV Design

Ferrite magnets and aluminium winding

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Evoque_e / Concept_e MHEV Design

Ferrite spoke magnets with novel rotor construction

M. Kimiabeigi, J. D. Widmer, R. Long, Y. Gao, J. Goss, R. Martin, T. Lisle, J.M. Soler Vizan, A. Michaelides, B. Mecrow On Selection of Rotor Support Material for a Ferrite Magnet Spoke Type Traction Motor , IEMDC 2015, USA

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High Performance Motorsport Motor

High torque density motor for motorsport

On-LoadOpen Circuit Iron Loss (On-Load)

Magnet Loss(Over One Cycle)

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High Performance Motorsport Motor

Complex cooling system with multiple cooling circuits Calculated efficiency map and drive cycle analysis for LeMans circuit in few mins

-2000200

0

20000

0 500 1000 1500 2000 2500 3000

Motor Speed & Torque (LeMans)

Motor Speed Motor Torque

Fast duty cycle analysis ideal for sizing of motor for race circuit and/or size the required cooling system

20 Laps of LeMans Circuit

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Performance Prediction for Nissan LEAF MotorMuch data available on

internet for Nissan LEAF motor

Developed models to validate & demonstrate software tools for modelling traction applications

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Performance Prediction for Nissan LEAF Motor

Predicted efficiency map validated by test data

Thermal model validated by 50kW, 60kW, 70kW, 80kW thermal transient test data

good match

Motor-LAB

Measured

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Drive Cycle Prediction (Nissan LEAF)

Prediction of efficiency map and 10 repetitive US06 Drive Cycle thermal transient in a few minutes

Torque vs time

Speed vs time

Total Loss

Copper Loss

Iron Loss

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Continuous Software Development

Many users in various industrial sectors

Automotive (Bosch, BMW, Daimler, GM, JLR, Nissan, Porsche, Remy, Renault …...)

Aerospace (Ametek, BAE, Eaton, Thales, Safran, Goodrich, UTC …….)

Industrial (ABB, Emerson, Regal Beloit, SEW, Siemens .……)

Traction (ABB, Bombardier, Caterpillar, GE, Komatsu….…)

Renewable (Alstom, Gamesa, GE, Siemens, Vestas ……)

Universities (Bristol, Manchester, Newcastle, Nottingham, Sheffield ……)

Software has been under continual development over the past 18 years with feedback from its hundreds of users worldwide

New features driven by user requirements

Work closely with our customers

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Summary

Machine design choices are complex and state of the art modelling tools are required to inform these choices

Motor-CAD is fast to simulate and constantly validated against test data

It can be used by experts and non-experts in the various physical domains

Design choices can be compared very quickly – even with complex drive cycle analysis