North Bay Electric Auto Association

1
North Bay Electric Auto Association Summer 2009
Technical Series Electric Vehicle Drive
Systems www.nbeaa.org Presented June 13,
2009 Corrected June 15, 2009 This presentation is
posted at http//www.nbeaa.org/presentations/driv
e_systems.pdf
2
NBEAA Summer Technical
Series TODAYgtgt 1. EV Drive Systems 2. EV
Batteries and Management Systems 3. EV
Charging Systems 4. EV Donor Vehicles
3
Agenda What is an EV Drive System? EV
Drive System History EV Drive System
Requirements Types of EV Drive Systems EV Drive
System Cooling EV Drive System Management EV
Drive System Comparison Future EV Drive
Systems EV Drive System Testimonials, Show and
Tells and Test Drives
4
What is an EV Drive System?
To Wheel
From Battery
CV Joint
From Driver
Motor controller
Half Shaft
CV Joint
Fly- wheel and Clutch
Trans-mission
Differ-ential
Motor Adapter
U Joint
U Joint
Drive Shaft
Motor
CV Joint
Half Shaft
CV Joint
All or a subset of the components between the
batteries and the wheels shown above.
To Wheel
5
What is an EV Drive System?

• Demonstration of electric motor principles
• Two permanent magnets attracting and repelling
  each other
• An electromagnet attracting and repelling a
  permanent magnet with a DC source, reversed with
  polarity
• A small brushed permanent magnet DC motor,
  speed increased with varying voltage through
  variable resistor, and reversed with polarity

6
EV Drive System History
First electric motor, for demonstration only 1821 England Michael Faraday
First DC motor that could turn machinery 1832 England William Sturgeon
First electric carriage, 4 MPH with non-rechargeable batteries 1839 Scotland Robert Anderson
First DC motor that was commercially successful 1873 Belgium Zenobe Gramme
First AC motor 1888 US Nikola Tesla
First mass produced electric vehicle, with variable resistor DC motor control 1914 US Thomas Edison and Henry Ford
First high efficiency small air gap motors 1950s US
First SCR controllers 1960s US
First MOSFET PWM controllers 1970s US
First IGBT PWM controllers 1980s US
First digital configuration PWM controllers 1990s US
First digital control PWM controllers 2000s US
7
EV Drive System Requirements Safe High
Power High Efficiency Durable
8
EV Drive System Requirements Safe Examples of
EV drive system safety issues Short
Circuit common DC motor controller failure
mode, exacerbated by high currents and hence
high heat probability reduced with improved
efficiency response enhanced with a clutch,
circuit breaker and automatic contactor
controller Low power some more efficient or
lower cost setups with low power could expose
vehicle to oncoming traffic overheating
undersized or poorly controlled systems could
induce thermal cutback that can exacerbate this
9
EV Drive System Requirements High Power Power
Watts Volts x Amps Power out power in x
efficiency of portion of system being
evaluated at the output shaft or at the
brake pads 1 Horsepower 746 Watts Motor
controller efficiency gt90 Motor efficiency
85-95 Rest of drive train efficiency
85-90 Overall efficiency 65-75 25-35 lost
due to heat
10
EV Drive System Requirements High
Power Example Accelerating or driving up a short
steep hill Peak Motor Shaft Power 50 HP or
37,000 W Peak Motor Current 500A for 144V
nominal pack with DC drive 200A RMS for 288V
nominal pack with AC drive Driving steady state
on flat ground at high speed Continuous Motor
Shaft Power 20 HP or 15,000 W Continuous
Motor Current 200A for 144V nominal pack with
DC drive 75A RMS for 288V nominal pack with
AC drive Regenerative Braking Depends on
battery type Example 3C max charge Thunder Sky
LFP series LiFePO4 180A for 60 Ah cells 270A
for 90 Ah cells
11
EV Drive System Requirements High Efficiency
Power losses due to heat cause power and range
reduction.
Bearing heat x5
Switching Transistor, freewheel diode heat
CV Joint
Motor controller
Half Shaft
Bearing heat
Bearing heat
Bearing heat
Copper, bearing heat
CV Joint
Fly- wheel and Clutch
Trans-mission
Differ-ential
Motor Adapter
U Joint
U Joint
Drive Shaft
Motor
CV Joint
Half Shaft
CV Joint
The more current, the more load, and hence the
more heat is lost throughout.
12
EV Drive System Requirements Durable Wide range
of driving requirements combined with downwards
pressure on size and weight for performance and
cost reasons can put excess stress on drive
system components Harsh automotive environment
much worse than indoor environment
temperature -40C to 50C humidity 5 to
condensing shock potholes vibration gravel
roads Make sure to use a motor for and EV that
was intended for on-road use.
13
Types of EV Drive Systems Which Type is
Best? AC vs. DC AC is more efficient, less
maintenance and more robust DC is less
expensive, but mainly due to higher volume fork
lift industry trend is moving from DC to AC late
model OEM EVs have mostly been AC conversions
mostly DC Transmission or fixed
gear Transmission is more efficient Fixed gear
is lighter and less complex Clutch or no
clutch Clutch is more efficient No clutch is
lighter and less complex The debate rages on,
but the highest performance is AC with
transmission and clutch.
14
Types of EV Drive Systems Motor
Terminology Rotor rotating part of
motor Stator stationary part of
motor Field produces magnetic field to be
acted upon by armature can be electromagnet
or permanent magnet Armature carries current
normal to field to generate torque Rotor or
stator can be either field or armature.
15
Types of EV Drive Systems Motor Comparison
type brushes Stator Rotor
DC Series Yes Field windings Armature windings, commutated through brushes and split rings, in series with field
DC Shunt Yes Field windings Armature windings, commutated through brushes, separately excited from field
DC Brushed Permanent Magnet Yes Field permanent magnet Armature windings, commutated through brushes
DC Brushless Permanent Magnet No Armature windings, PWMd via rotor position sensor Field permanent magnet
AC Synchronous Yes Armature windings, PWMd via rotor position sensor Field windings, DC energized through brushes and slip rings
AC Induction No Armature windings, PWMd via rotor position sensor Opposing magnetic field induced via eddy currents caused by slip between stator and rotor in copper or aluminum squirrel cage frame
16
Types of EV Drive Systems
Category Type Example Motors Example Controllers
DC Series Advanced DC Kostov2 Netgain Alltrax Auburn3 Café Electric1 Curtis Raptor1
Shunt DD Alltrax Sevcon
Brushed Permanent Magnet Perm PMG Et-R, RT Alltrax
Brushless Permanent Magnet Mars Toyota RAV4 EV3 Sevcon Toyota RAV4 EV3
AC Synchronous Siemens2 Siemens2
Induction AC Propulsion Azure Dynamics Brusa Curtis MES Siemens2 AC Propulsion Azure Dynamics Brusa Curtis MES Siemens2
Notes 1 Requires special order, 2 are no longer
readily available in the US, 3 are obsolete.
17
Types of EV Drive Systems Drivelines
Shaft Type Fit for flywheel and clutch? Picture
Smooth Keyed Yes
Splined No
Involuted Spline Heck No
18
Types of EV Drive Systems Motor Control via
Pulse Width Modulation
100 duty cycle 75 50 25 0
19
Types of EV Drive Systems Switch Mode Power
Supply Buck Regulator
Motor Armature (and field for DC series separate
circuit for DC shunt and AC synchronous)
Freewheel diodes
Filter capacitors
From batteries
From PWM control circuit
Power switching transistors (MOSFETs or IGBTs)
When power is applied to input, capacitors are
charged up. When transistors are switched on,
current flows from the batteries and capacitors
to the motor. When the transistors are off, the
capacitors are recharged by the batteries while
current flows from the motor to the freewheel
diodes while the motors magnetic field collapses
to keep from increasing the voltage across the
transistor to the point of failure.
20
Types of EV Drive Systems 3 Phase AC
Configurations
wye
delta
A
A
B
B
C
C
Coil voltage line voltage RPM varies with
voltage Used at lower voltages to maximize speed
Coil current line current Torque varies with
current Used at higher voltages to maximize torque
21
Types of EV Drive Systems PWM control circuit
types Analog Digital configuration Digital
control
22
Types of EV Drive Systems Cooling Systems
Type Motor Motor Controller
Sealed, no fan Center may overheat Needs large area heat sink can be flat plate
Sealed, external fan on heat sink Takes up a single large fixed volume
Sealed, liquid Requires small cooling system Requires small cooling system
Internal fan, open Needs debris and splash shield low slung motor can not be submerged May corrode due to humidity, or overheat due to dust accumulation
External fan, open Takes up more volume Needs debris and splash shield low slung motor can not be submerged
23
Types of EV Drive Systems Management
Systems Voltage (speed) or current (torque)
regulation vs. pedal (potbox or hall effect)
input Motor current limiting Battery current
limiting Low pack voltage cutoff Low cell voltage
cutoff Motor controller thermal cutback Motor
thermal cutback Battery thermal cutback
24

EV Drive System Comparison
Type Safety Efficiency Torque Regen
DC Series
DC Shunt
DC Brushed PM
DC Brushless PM
AC Synchronous
AC Induction
25
EV Drive System Comparison
Controller Curtis 1231C-8601 Raptor 600 Cafe Electric Zilla 1K-LV Raptor 1200 Cafe Electric Zilla 2K-LV Solectria DMOC445 MES-DEA TIM600
Motor Advanced DC 9" FB1-4001 Advanced DC 9" FB1-4001 Advanced DC 9" FB1-4001 Advanced DC 9" FB1-4001 Advanced DC 9" FB1-4001 Solectria AC24 w/smooth keyed output shaft MES 200-150
Peak HP at 144V 72 86 144 172 288 58 73
Continuous HP 28 28 28 28 28 24 19
Peak Torque at 144V, ft-lb 110 132 220 264 440 55 118
Regenerative Braking no no no no no yes yes
Efficiency 75 75 75 75 75 85 85
Output Shaft smooth keyed smooth keyed smooth keyed smooth keyed smooth keyed smooth keyed involuted spline, but 8.641 Carraro gearbox with differential available
Sealed Controller? yes no yes no yes yes yes
Brushes? yes yes yes yes yes no no
Cooling air air with internal fan water, controller only air with internal fan water, controller only air water, motor and controller
adjustable battery minimum voltage (and maximum if regen) no ? yes ? yes yes yes
independent main contactor safety control no ? yes ? yes yes yes
accelerator modulation speed ? torque ? torque torque torque
Motor and Controller Weight, lbs 170 170 170 190 190 117 121
System Price 3,000 3,000 3,500 3,500 4,000 6,500 12,000
Example to be updated
Other Drive Systems Not Considered- Solectria
AC55 too heavy at 234 lbs, aand splined shaft
with no matching gearbox, requiring custom
differential gear machining or non-standard
flywheel coupling. - MES 200-175 28 HP exceeds
rating of Carraro gearbox, leaving an involuted
spline, not good for a flywheel.- Siemens AC
also splined shafts only with no matching
gearbox. And they are surplus, so they might be
hard to get support for, but they do carry a 10
year warranty.- Brusa AC also splined shaft
with no matching gearbox.- AC Propulsion cost
prohibitive at 25KK for 150 kW system (although
it includes high power charging).- Kostov series
wound DC motors not readily available.- Auburn
series DC controllers company no longer in
business.- Curtis 1244 Sep-Ex shunt DC regen
controller complex with marginal performance.-
Zapi Sep-Ex shunt DC regen controller same as
above.- Customized series wound DC motor with
variable mechanical brush timing to improve
forward and regen efficiency too many parts-
Dual DC with no transmission too inefficient.
60 efficiency estimated. The following AC drive
systems are under development or are currently
not available to hobbyists Enova, UQM, TM4,
Reliance, AC Electric Vehicles
26
EV Drive System Comparison
27
EV Drive System Comparison Advanced DC 9 Series
DC at 120V
28
EV Drive System Comparison DD Shunt SepEx DC
at 72V
29
EV Drive System Comparison DD Shunt SepEx DC
at 72V
30
EV Drive System Comparison PMG 132 Brushed
Permanent Magnet DC at 72V
31
EV Drive System Comparison Et-RT Brushed
Permanent Magnet DC at 48V
32
EV Drive System Comparison Azure Dynamics
AC24LS/DMOC445 delta at 156V
33
EV Drive System Comparison Azure Dynamics
AC24LS/DMOC445 delta at 156V
34
EV Drive System Comparison Azure Dynamics
AC24LS/DMOC445 wye at 312V
35
EV Drive System Comparison Azure Dynamics
AC24LS/DMOC445 wye at 312V
36
Future EV Drive Systems Even more efficient
motors and motor controllers? 4 wheel hub
motors? 4 inboard wheel motors? Fully
integrated braking systems? Nano-capacitor
driven motor controllers? Optical pedal input?
37
EV Drive System Testimonials, Show and Tells and
Test Drives
Peter Oliver Azure Dynamics AC24 motor and
DMOC445 controller in Porsche Speedster
conversion (http//www.evalbum.com/1683) AC 55
motor Brian Hall Curtis 96V AC drive system
in 72V Geo Metro conversion 72V Et-RT permanent
magnet brushed DC motor Chris Jones 9
Advanced DC motor and Curtis 1231C motor
controller in Ford Mustang conversion
(http//www.evalbum.com/733)
38
Things to add in future 0-60 MPH comparison
DC, AC, gasoline Diagrams and graphs for each
motor and controller type Movies for each motor
and controller type Update table comparing all
parameters of all drive systems Overlays of motor
curves Written descriptions of how to read motor
curves More detailed written descriptions of how
motors and motor controllers work References