electric vehicle drive systems

North Bay Electric Auto Association

Summer 2009 Technical Series

Electric Vehicle Drive Systemswww.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


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 JointHalf

Shaft

CV Joint

CV JointHalf

Shaft

To Wheel

To Wheel

From Driver


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

US1990sFirst digital configuration PWM controllers

US1980sFirst IGBT PWM controllers

US1950sFirst high efficiency small air gap motors

US1960sFirst SCR controllers

US2000sFirst digital control PWM controllers

1970s

1914

1888

1873

1839

1832

1821

US

US

US

Belgium

Scotland

England

England

Thomas Edison and Henry Ford

Nikola Tesla

Zenobe Gramme

Robert Anderson

William Sturgeon

Michael Faraday

First MOSFET PWM controllers

First mass produced electric vehicle, with variable resistor DC motor control

First AC motor

First DC motor that was commercially successful

First electric carriage, 4 MPH with non-rechargeable batteries

First DC motor that could turn machinery

First electric motor, for demonstration only

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 couldinduce 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 JointHalf

Shaft

CV Joint

CV JointHalf

Shaft

Switching Transistor, freewheel diode heat

Copper, bearing heat

EV Drive System Requirements: High EfficiencyPower 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 robustDC 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 togenerate torque

Rotor or stator can be either field or armature.

Types of EV Drive Systems: Motor Comparison

No

Yes

No

Yes

Yes

Yes

brushes

Opposing magnetic field induced via eddy currents caused by slip between stator and rotor in copper or aluminum “squirrel cage” frame

Armature windings, PWM’dvia rotor position sensor

AC Induction

Field windings, DC energized through brushes and slip rings

Armature windings, PWM’dvia rotor position sensor

AC Synchronous

Field permanent magnetArmature windings, PWM’dvia rotor position sensor

DC Brushless Permanent Magnet

Armature windings, commutated through brushes

Field permanent magnetDC Brushed Permanent Magnet

Armature windings, commutated through brushes, separately excited from field

Field windingsDC Shunt

Armature windings, commutated through brushes and split rings, in series with field

Field windingsDC Series

RotorStatortype

Types of EV Drive Systems

Siemens2Siemens2SynchronousAC

AlltraxPerm PMGEt-R, RT

Brushed Permanent Magnet

AC PropulsionAzure DynamicsBrusaCurtisMESSiemens2

MarsToyota RAV4 EV3

D&D

Advanced DCKostov2

Netgain

Example Motors Example ControllersTypeCategory

Induction

Brushless Permanent Magnet

Shunt

Series

AC PropulsionAzure DynamicsBrusaCurtisMESSiemens2

SevconToyota RAV4 EV3

AlltraxSevcon

AlltraxAuburn3

Café Electric1

CurtisRaptor1

DC

Notes: 1 Requires special order, 2 are no longer readily available in the US, 3 are obsolete.

Types of EV Drive Systems: Drivelines

Heck No

No

Yes

Fit for flywheel and clutch?

Involuted Spline

Splined

Smooth Keyed

PictureShaft Type

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

Takes up a single large fixed volume

Sealed, external fan on heat sink

Requires small cooling system

Requires small cooling systemSealed, liquid

Takes up more volume; Needs debris and splash shield; low slung motor can not be submerged

Needs debris and splash shield; low slung motor can not be submerged

Center may overheat

Motor

Needs large area heat sink; can be flat plate

Sealed, no fan

External fan, open

May corrode due to humidity, or overheat due to dust accumulation

Internal fan, open

Motor ControllerType

Types of EV Drive Systems: Management Systems

Voltage (speed) or current (torque) regulation vs. pedal (potboxor hall effect) input

Motor current limitingBattery current limitingLow pack voltage cutoffLow cell voltage cutoff

Motor controller thermal cutbackMotor thermal cutback

Battery thermal cutback


+

+

+

~

~

~

Regen

~

~

~

~

~

+

Torque

+

+

+

~

~

~

Efficiency

+AC Induction

+AC Synchronous

+DC Brushless PM

~DC Brushed PM

~DC Shunt

~DC Series

SafetyType


$12,000 $6,500 $4,000 $3,500 $3,500 $3,000 $3,000 System Price

121 117 190 190 170 170 170 Motor and Controller Weight, lbs

torque torque torque ? torque ? speed accelerator modulation

yes yes yes ? yes ? no independent main contactor safety control

yes yes yes ? yes ? no adjustable battery minimum voltage (and maximum if regen)

water, motor and controller air water, controller only

air with internal fan

water, controller only

air with internal fan air Cooling

no no yes yes yes yes yes Brushes?

yes yes yes no yes no yes Sealed Controller?

involuted spline, but 8.64:1 Carrarogearbox with differential available smooth keyed smooth keyed smooth keyed smooth keyed smooth keyed smooth keyed Output Shaft

85% 85% 75% 75% 75% 75% 75% Efficiency

yes yes no no no no no Regenerative Braking

118 55 440 264 220 132 110 Peak Torque at 144V, ft-lb

19 24 28 28 28 28 28 Continuous HP

73 58 288 172 144 86 72 Peak HP at 144V

MES 200-150 Solectria AC24 w/smooth keyed output shaft

Advanced DC 9" FB1-4001




Advanced DC 9" FB1-4001 Motor

MES-DEA TIM600 Solectria DMOC445 Cafe Electric Zilla 2K-LV Raptor 1200 Cafe Electric

Zilla 1K-LV Raptor 600 Curtis 1231C-8601 Controller

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 ComparisonAdvanced DC 9” Series DC at 120V

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 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

electric vehicle drive systems

Documents