MotorSolve analysis of the 2010 Toyota Prius Traction Motor.

MotorSolve analysis of the 2010 Toyota Prius Traction Motor. Presented by: James R Hendershot Location: Hilton Rosemont, Chicago O Hare Date: Oct. 27, 2015 Hendershot 2015 Copyright 1

Presenter: James R Hendershot Jim has over 40 years experience in practical hands-on PM & SR brushless motor design, manufacturing and development. With past key employments at United Technologies, General Motors, Clifton Precision, Berger Lahr & Pacific Scientific, he has designed hundreds of brushless motors for computer disc drives, servo systems, high speed machine tool spindles, traction drives, hybrid vehicles, micro-turbine and diesel generators. He has written numerous technical papers, publications and presented tutorials on many different electric motor topics. Hendershot is the co-author with Professor TJE Miller for two of the leading design books on Permanent books on Permanent Magnet Motor and Generator Design (ISBN 1-881855-03-1, 1994 & ISBN 978-0-9840687-0-8, 2010). Jim teaches detailed motor design training courses (including workshops) at public venues, conferences and custom designed workshops tailored on-site for companies around the World. Jim Hendershot holds a B.S in Physics from Baldwin Wallace University in Berea Ohio along with additional E.E. & M.E. engineering studies at Cleveland State University as well as graduate courses at Case-Western University in Cleveland Ohio. He specializes in the design, analysis, sourcing, manufacturing and teaching of both electro-magnetic and permanent magnetic devices. In addition to continuing studies in magnetics and electric machines. Jim has enjoyed a long and rich association with Dr. Tim Miller, founder of the SPEED Consortium at the University of Glasgow combining Jim s practical hands-on motor design skills with TIM S theoretical knowledge and research For the past few years Jim has also been associated with Infolytica Corp, Prof. Dave Lowther (of McGill University), Prof. Ernie Freeman retired from Imperial College, London and their staff for continued development and research involving the design and research for electric motors and generators. Jim Hendershot developed a Dyno-Kit for teaching electric motor drives used by over 120 US Universities and Colleges for Prof. Ned Mohan of the University of Minnesota. These are used for the lab portion of their Electric Drive Courses. Jim Hendershot has created a series of 36 electric machine design lectures for the University of Minnesota, funded by the US Navy Research Labs that are available on YouTube. (9 to 10 hrs. of lectures covering all aspects of practical electric machine design). Hendershot 2015 Copyright 2

For thousands of years man could only walk here and there. By 4000 to 5000 BC man began to ride horses Around 2000 BC horses were used to pull carts and carriages Early US settlers used horse & oxen drawn large wagons to go West (Like modern RVs & campers) In 1605 horse drawn carriages were used on the streets of London. By 1640 the London horse drawn carriages added springs for comfort and with a driver. Hendershot 2015 Copyright 3

Introduction In the late 19 th and early 20 th century, electricity was the preferred power source for automobile propulsion. US had no highway systems because passenger trains were used for long distance travel. Gasoline was known but no infrastructure available Steam powered cars were also tried. By 1920 thanks to Henry Ford, IC engine improvements and the growing petroleum infrastructure, thanks to John D Rockefeller, gasoline power dominated automobiles until this present day. Hendershot 2015 Copyright 4

History summary of automobile propulsion: 1768 French steam engine powered car by Nicolas Cugnot 1832 Robert Anderson ran first electric motor driven car 1885 Karl Benz made first 4 wheel gas powered car 1888 First noted (4) wheel E-Car, Flocken Elektrowagen 1893 First American car was developed by Charles Duryea 1897 Stanley Steamer in Newton MA, sold 200 cars 1908 Ford Model-T introduced (Internal combustion gasoline powered engine) Hendershot 2015 Copyright 5

1888 Flocken Early examples of E-Vs 1907 Detroit 1910 POPE 1912 Edison Limited gasoline availability and cars needed for only short trips. Trains used for long distances) First lead-acid storage batteries developed in 1859 Frenchmen named Gaston Planté 1918 Woods Hendershot 2015 Copyright 6

First (serious?) electric car since in nearly 100 years EV1 by General Motors Hendershot 2015 Copyright 7

EV1 by General Motors Production years 1996 to 1999 EV1s total produced total 1117 cars Range 70 to 90 miles per charge Motor type, (3) phase aluminum rotor AC induction motor Maximum output power = 103 kw Peak output torque = 149 Nm Base speed = 6500 rpm Max speed = 13000 rpm Hendershot 2015 Copyright 8

Toyota Motor Car Corp. EV or Hybrid development Sometime in the middle 90s, Toyota began development of a hybrid electric vehicle to compete with the GM EV1. First production in Japan in 1997 (before the EV1 was cancelled by GM in 2003.) Toyota PRIUS first sold in the USA in 2003 Second generation PRIUS sold in USA in 2004 Third generation PRIUS sold in USA in 2010 Fourth generation PRIUS in USA scheduled for 2016 Hendershot 2015 Copyright 9

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World hybrid Hybrid/EV sales 2003 to mid 2015 Total world production of hybrid or electric vehicles since 2003 = 3,540,199 Total world production of Toyota s share = 2,487,564 ( 70%) Total world production of Prius share = 1,731,717 (49%) 755,847 difference from other hybrid models designed & sold by Toyota such as, Camry, Avalon, Highlander & Lexus. Hendershot 2015 Copyright 11

Electric traction motor options for hybrid and EV vehicles. IM RSM IM, RSM & IPM/SPM use similar stators & phase windings with different rotors IPM or SPM Switched Reluctance New rotor & stator Hendershot 2015 Copyright Cross sections of electric machines by: 12

Maximum flux densities of materials limit performance No matter which machine you choose for a motor/generator its torque density is limited by two important magnetic materials. 1-Hard materials (permanent magnets) can only produce a maximum flux density of 1.4 tesla 2-Soft materials (electrical steels) become saturated at maximum flux densities in the range of 2.1 to 2.4 Tesla I offer each of you a challenge to invent new materials A new material with a negative permeability would be a good start, then higher temperature super conductivity materials Hendershot 2015 Copyright 13

Specific power density of current piston engines, turbines & electric motors Cooling and efficiency are very important for electric propulsion Hendershot 2015 Copyright 14

Power density of modern EV traction motors Hendershot 2015 Copyright 15

ELECTRIC MACHINE POWER DENSITY COMPARISONS TESLA 4.5 kw/kg (225 kw peak for 30 sec.) New TESLA 4.34 kw/kg BMW i3 = 2.5 kw/kg (at 125 kw max) Siemens 5 kw/kg Aero PM motor (260 kw @ 50 kg) Hendershot 2015 Copyright 16

Review of the Toyota Prius PM-AC traction motors Toyota selected the PM-AC synchronous motor because it has the highest power density, highest power factor, highest efficiency and easiest to cool of any known electric machine. (Perhaps a bit more expensive than that other choices due to use of rare earth magnets. However if AC Induction motors are used they must use copper rotors which increases their costs also. (The extra difficulty of rotor cooling and lower power factor tends to offset the magnet cost of the PM-AC machines.) There are two types of PM-AC synchronous machines, SPM & IPM. IPMs were chosen for several important reasons for automobile traction. Wide constant power speed range range Robust rotor without additional retainment Lower cost rectangular permanent magnets (no grinding required) Added reluctance torque output from same source current for magnet torque Hendershot 2015 Copyright 17

Two types of PM-AC synchronous machines, SPM & IPM. Hendershot 2015 Copyright 18

Prius 2003 IPM style (8 poles) Prius 2004 IPM style (8 poles) The magnets & pole tops are retained against centrifugal forces by thin webs at the magnet ends. Careful stress analysis is required as well as field solutions to minimize flux leakage. (Said to be as high as 20 % leakage) Hendershot 2015 Copyright 19

Toyota IPM rotor dimensions Hendershot 2015 Copyright 20

Rotor Punching comparison for IPM Toyota electric traction motors Actual Prius rotor punching has mass reduction pockets that also facilitate cooling. This can be modeled by importing a cad created rotor DXF file in MotorSolve or in MagNet. Hendershot 2015 Copyright 21

PM Generator rotor for 2004 Prius 2010 Toyota Prius PM generator 12 slot, 8 IPM poles, V shaped PM Generator for 2010 Prius Hendershot 2015 Copyright 22

Model (reverse engineer) 2010 TOYOTA PRIUS traction motor 1-Using Infolytica s powerful electric motor template based Field Solver known as MOTORSOLVE, we can load the program, select motor type-brushless DC motor, answer no to sizing question. 2-Select General Settings & fill out the input parameters taken from the data provided by ORNL on slides 23, 24 & 25. 3-Select Stator and fill in the required inputs also from the ORNL slide data 4-Then select Rotor and fill in the required inputs from the ORNL slides 5-Select Stator Windings and fill in the phase winding data from the ORNL slides 6-Select Materials and select both the electrical steel and the magnet grade from the list provided. 7-Solve for various performance Results, compare with ORNL test data & learn how to design these types of IPM PM-AC synchronous machines. Hendershot 2015 Copyright 26

The input results, right side under General Settings, left side Input values from ORNL data Note: the cross section will not look like the one shown until after all rotor and stator inputs are complete Hendershot 2015 Copyright 27

No rotor template is available that allows the creation of extra holes inside used for mass reduction and cooling. This can be created using CAD & imported as a.dxf file The open circuit air gap flux density can be compared Rotor IPM With variable orientation Rotor IPM DXF imported Hendershot 2015 Copyright 28

Stator inputs Select: Stator (round) Input values from ORNL data Hendershot 2015 Copyright 29

Setting the IPM rotor parameters Select: Rotor (with variable orientation) Input values from ORNL data A long & careful study of web thickness, magnet width & orientation angle required to optimize the reluctance torque & magnet torque. Hendershot 2015 Copyright 30

Typical total torque output of an IPM machine equals reluctance torque plus magnet torque Peak torque @ angle = 36 deg. PM torque function of magnet grade, Perm. Coef. & magnet area Reluctance torque function of salient pole width & Inductance ratio Hendershot 2015 Copyright 31

Varying the web between magnetic poles from 1 to 8 mm Critical design task for IPM design Web thickness effects the saliency L q & L d ratio Balance the magnet torque and the reluctance torque Requires many tedious trial magnetic field solutions As web gets larger, the magnet V angle increases. There are many variations possible, such as multiple magnet layers & flux barriers. Hendershot 2015 Copyright 32

D & Q axis torque plots of 2010 Prius motor Saliency width I 30 deg. E optimum gamma angle for max torque 6 deg. M advance d q Hendershot 2015 Copyright 33

Phase Winding layout Select: Stator (round) Note: This is a single layer winding (one coil side per slot). Input values from ORNL data Hendershot 2015 Copyright 34

Winding slot position list Phase Windings are Selected based upon highest Winding Factor Hendershot 2015 Copyright 35

Material selection, for shaft, magnets, stator core, rotor core & conductors Select: Materials Select material choices from those included in data bases or add new materials. Hendershot 2015 Copyright 36

Simulated back EMF (O.C.) @ 7200 rpm The back emf can be simulated at any RPM setting. This example is at 7200 RPM, the speed where the back EMF equals 650 VDC peak, or the same voltage as the DC rail voltage. Without field weakening Hendershot 2015 Copyright 37

Simulated back EMF (O.C.) @ 13,500 rpm With no field weakening the back emf is about 1300 VDC peak at 13,500 rpm. This means that Toyota used field weakening which can be modeled using a current advance angle. Hendershot 2015 Copyright 38

Cogging torque simulation @ 100 rpm Number of data point settings Accuracy settings Increase from 1 default to 3 Select: Cogging torque Hendershot 2015 Copyright 39

Open Circuit flux distribution Note: High leakage flux in bridges & posts required for magnet retention Hendershot 2015 Copyright 40

Simulated back EMF (O.C.) @ 1000 rpm From choice of phase & line Select: Line, Phase Slightly less than 100 V peak at 1Krpm Select :Back EMF Hendershot 2015 Copyright 41

O.C. back emf with one stator slot skew (1000 rpm) Under stator design, set skew to 7.5 (Deg.) and solve for Back EMF Note: Slight skew (rotor or stator) shapes the line to line back EMF closer to a true sine wave reducing harmonics Hendershot 2015 Copyright 42

Air gap flux plot with standard TOYOTA IPM rotor Peak air gap flux ~ 0.8 T Result of leakage flux from IPM post & bridge Hendershot 2015 Copyright 43

O.C. flux plot with zero magnet to magnet leakage inside rotor Post & bridge values set to zero to prevent leakage form magnet to magnet in rotor Hendershot 2015 Copyright 44

O.C. Back Emf plot with zero magnet to magnet leakage At 1000 rpm & zero internal rotor leakage the peak back EMF has increased from 100 V to about 145 V Hendershot 2015 Copyright 45

O.C. air-gap flux plot with zero magnet to magnet leakage Peak air gap flux ~ 1.0 T With zero leakage from IPM post & bridge. This leakage represents 20% loss in flux linkage Hendershot 2015 Copyright 46

Setup for simulation of torque including magnet & reluctance components Select: PWM analysis Select: Torque, Magnet & Reluctance Set angles: 0, 90, 5 Hendershot 2015 Copyright 47

Torque vs Speed plots, 650 VDC, 0 advance and 45 deg. advance angles Select: Torque vs. speed Note: generating region Input: Advance angle 0, 45 Speed, 100, 13500, 100 Hendershot 2015 Copyright 48

Torque vs Speed plots, 650 VDC, 0 advance and 35 deg. advance angles Note: generating region Input: Advance angle 0, 45 Speed, 100, 13500, 100 Current reduced 25% Hendershot 2015 Copyright 49

Torque vs RPM plots, 0 to 45 deg. Advance (650 VDC bus) Note: With zero advance, 7200 rpm is max. speed attainable with 650 VDC. Hendershot 2015 Copyright 50

2010 Toyota Prius 8 pole, 48 slot IPM machine Thermal analysis by Adrian Perregaux Hendershot 2015 Copyright 53

3D model for thermal analysis Thermal analysis by Adrian Perregaux Hendershot 2015 Copyright 54

Output torque vs current (Toyota 2010 Prius) Hendershot 2015 Copyright Adrian Perregaux

2010 Toyota Prius cooling analysis by internal oil spray cooling Thermal analysis by Adrian Perregaux Hendershot 2015 Copyright 56

Peak flux distribution of Prius 2010 motor 45 deg. advance 1.92 T in teeth 200 Nm 150 A Thermal analysis by Adrian Perregaux Hendershot 2015 Copyright 57

Open circuit flux distribution of Prius 2010 motor Thermal analysis by Adrian Perregaux Hendershot 2015 Copyright 58

Temperature rise of key components @ 70% duty cycle Thermal analysis by Adrian Perregaux Hendershot 2015 Copyright 59

Simulated vs. measured temperature rise Deg. C vs. seconds Thermal analysis by Adrian Perregaux Hendershot 2015 Copyright 60

Efficiency Plot of 2010 Toyota Prius motor (Motorsolve) Linearized efficiency plot for fast solution time Select Efficiency and set up with parameters on right Hendershot 2015 Copyright 61

Efficiency Plot of 2010 Toyota Prius motor (Motorsolve) Linearized efficiency plot (Takes about one hr. to solve) Hendershot 2015 Copyright 63

ISBN 0-19-859389-9 ISBN 978-0-9840687-0-8 RED BOOK GREEN BOOK Hendershot 2015 Copyright 64