north bay electric auto association summer 2009 technical series electric vehicle drive systems ...
TRANSCRIPT
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/drive_systems.pdf
NBEAA Summer Technical Series
TODAY>> 1. EV Drive Systems
2. EV Batteries and Management Systems
3. EV Charging Systems
4. EV Donor Vehicles
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
What is an EV Drive System?
Motor
Fly- wheel and
Clutch
Trans-mission
Drive Shaft Differ-ential
Motor Adapter
All or a subset of the components between the batteries and the wheels shown above.
Motor controller
From Battery
U Joint
U Joint
CV Joint
CV Joint
Half Shaft
CV Joint
CV Joint
Half Shaft
To Wheel
To Wheel
From Driver
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
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
EV Drive System Requirements
Safe
High Power
High Efficiency
Durable
EV Drive System Requirements: Safe
Examples of EV drive system safety issues:
Short Circuitcommon DC motor controller failure mode, exacerbated
by high currents and hence high heat
probability reduced with improved efficiencyresponse enhanced with a clutch, circuit breaker and
automatic contactor controller
Low powersome 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
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 = >90%
Motor efficiency = 85-95%
Rest of drive train efficiency = 85-90%
Overall efficiency 65-75%
25-35% lost due to heat
EV Drive System Requirements: High PowerExample
Accelerating or driving up a short steep hillPeak Motor Shaft Power = ~50 HP or ~37,000 WPeak 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 speedContinuous Motor Shaft Power = ~20 HP or ~15,000 WContinuous Motor Current
~200A for 144V nominal pack with DC drive ~75A RMS for 288V nominal pack with AC drive
Regenerative BrakingDepends on battery typeExample: 3C max charge Thunder Sky LFP series LiFePO4
180A for 60 Ah cells270A for 90 Ah cells
Motor
Fly- wheel and
Clutch
Trans-mission
Drive Shaft Differ-ential
Motor Adapter
Motor controller
U Joint
U Joint
CV Joint
CV Joint
Half Shaft
CV Joint
CV Joint
Half Shaft
Switching Transistor, freewheel diode heat
Copper, bearing heat
EV Drive System Requirements: High Efficiency
Power losses due to heat cause power and range reduction.
Bearing heat
Bearing heat
Bearing heat
Bearing heat x5
The more current, the more load, and hence the more heat is lost throughout.
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 50Chumidity: 5% to condensingshock: potholesvibration: gravel roads
Make sure to use a motor for and EV that was intended for on-road use.
Types of EV Drive Systems: Which Type is Best?
AC vs. DCAC is more efficient, less maintenance and more robust
DC is less expensive, but mainly due to higher volumefork lift industry trend is moving from DC to AClate model OEM EVs have mostly been AC; conversions mostly DC
Transmission or fixed gearTransmission is more efficientFixed gear is lighter and less complex
Clutch or no clutchClutch is more efficient No clutch is lighter and less complex
The debate rages on, but the highest performance is AC with transmission and clutch.
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.
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, PWM’d via rotor position sensor
Field permanent magnet
AC Synchronous Yes Armature windings, PWM’d via rotor position sensor
Field windings, DC energized through brushes and slip rings
AC Induction No Armature windings, PWM’d 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
Types of EV Drive SystemsCategory
Type Example Motors Example Controllers
DC Series Advanced DC
Kostov2
Netgain
Alltrax
Auburn3
Café Electric1
Curtis
Raptor1
Shunt D&D 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.
Types of EV Drive Systems: Drivelines
Shaft Type Fit for flywheel and clutch? Picture
Smooth Keyed Yes
Splined No
Involuted Spline Heck No
Types of EV Drive Systems: Motor Control via Pulse Width Modulation
100% duty cycle
75%
50%
25%
0%
Types of EV Drive Systems: Switch Mode Power Supply Buck Regulator
From batteries
Motor Armature (and field for DC series;
separate circuit for DC shunt and AC synchronous)
Power switching transistors (MOSFETs
or IGBTs)
From PWM control circuit
Freewheel diodes
Filter capacitors
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 motor’s magnetic field collapses to
keep from increasing the voltage across the transistor to the point of failure.
Types of EV Drive Systems: 3 Phase AC Configurations
delta wye
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
A AB
C
B
C
Types of EV Drive Systems: PWM control circuit types
Analog
Digital configuration
Digital control
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
Types of EV Drive Systems: Management Systems
Voltage (speed) or current (torque) regulation vs. pedal (potbox or hall effect) input
Motor current limitingBattery current limitingLow pack voltage cutoffLow cell voltage cutoff
Motor controller thermal cutbackMotor thermal cutback
Battery thermal cutback
EV Drive System Comparison
Type Safety Efficiency Torque Regen
DC Series ~ ~ + ~
DC Shunt ~ ~ ~ ~
DC Brushed PM ~ ~ ~ ~
DC Brushless PM + + ~ +
AC Synchronous + + ~ +
AC Induction + + ~ +
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 8.64:1 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
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
Example – to be updated
EV Drive System Comparison
EV Drive System ComparisonAdvanced DC 9” Series DC at 120V
EV Drive System ComparisonD&D Shunt “SepEx” DC at 72V
EV Drive System ComparisonD&D Shunt “SepEx” DC at 72V
EV Drive System ComparisonPMG 132 Brushed Permanent Magnet DC at 72V
EV Drive System ComparisonEt-RT Brushed Permanent Magnet DC at 48V
EV Drive System ComparisonAzure Dynamics AC24LS/DMOC445 delta at 156V
EV Drive System ComparisonAzure Dynamics AC24LS/DMOC445 delta at 156V
EV Drive System ComparisonAzure Dynamics AC24LS/DMOC445 wye at 312V
EV Drive System ComparisonAzure Dynamics AC24LS/DMOC445 wye at 312V
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?
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)
EV Drive System Testimonials, Show and Tells and Test Drives
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