Automotive Systems course (Module 07) - Charging systems for road vehicles

25 de novembro de 2016 | 1
SistemasAutomóveis
Charging Systems
Mário Alves (mjf@isep.ipp.pt)

SistemasAutomóveis
Outline
• Charging System
• definition, components, trends, requirements
• Alternator
• operational characteristics, evolution, manufacturers, types
• Electromagnet inductor alternator
• main components + assembly, rotor, stator, brushes, slip rings,
rectifier, voltage regulation
• Permanent magnet inductor alternator
• main differences, inner/outer inductor types, voltage regulation
• Cooling
• Future trends
• Glossary
• Recommended references

SistemasAutomóveis
Charging System: definition
• Electric components and circuits that act as electrical power
source in a vehicle
• the term “charging system” is preferred in the mechanical/automotive
domain, against “power source” (used in the electrical engineering
domain), to distinguish from “engine/mechanical power”
• Combines two primary energy sources
• chemical energy (from the battery)
• supplies electrical energy when engine is off, cranking and
whenever the alternator does not cope with the load
• mechanical energy (from the engine and from the vehicle’s
kinetic energy, in electric/hybrid vehicles)
• enables to generate electrical energy when the engine is
running, through a generator (dynamo or alternator)

SistemasAutomóveis
Charging System: basic block diagram
https://autoelectricalsystems.wordpress.com/2015/09/19/electric-power-system-of-a-vehicle/

SistemasAutomóveis
Charging System: main components
• Main components (typical charging system)
• battery assembly (may feature more than one battery)
• alternator assembly (alternator, voltage regulator, rectifier)
• electrical wiring, switches, relays, connectors/connection boxes
• fuses and circuit breakers
• alternator belt and indicator light
http://www.autozone.com/
https://www.2carpros.com/questions/buick-regal-1999-buick-regal-serpentine-belt-replacement

SistemasAutomóveis
Charging System: technology and market trends
• All figures are growing!
• > market (5.4% growth/year)
• > power demand (100 W/year)
• > cost weight % (of car cost)
http://ecomodder.com/forum/showthread.php/list-typical-electrical-loads-modern-car-7196.html
http://www.marketsandmarkets.com/Market-Reports/automotive-starter-motor-alternator-market-120529968.html
http://www.eetimes.com/document.asp?doc_id
=1272772&page_number=2

SistemasAutomóveis
Charging System: requirements
• Main requirements
• cope with the electrical power demand from all electrical/electronic
systems in the vehicle, in all operating conditions (RPM,
temperature, different number of electrical loads)
• mind the different types of electrical loads:
• guarantee a stabilized voltage, in all operating conditions
• reliable, light-weight, silent, low-cost
• energy-efficient (SOTA 80%)
• malfunction indicator
http://www.nairaland.com/2215208/photos-how-understand-dashboard-warning

SistemasAutomóveis
• Interplay between the two power sources
http://www.nairaland.com/2215208/photos-how-understand-dashboard-warning

SistemasAutomóveis
• Load types according to duty-cycle
• Continuous-operation electric loads
• always on
• e.g. fuel pump, fuel injectors, ignition, ECUs
• Prolonged-operation electric loads
• turned on for long periods
• e.g. head/tail lights, Multimedia, HVAC, radiator fan
• Sporadic-operation electric loads
• Turned on for short periods
• e.g. starter motor, power windows/roof/locks, wipers/washers, horn,
windows/mirrors defoggers, ABS/TCS/ESP, pre-heating systems
• These statistical properties must be accounted for
• dimensioning the battery/alternator (based on average power)
http://www.eetimes.com/document.asp?doc_id=1272772

SistemasAutomóveis
• Electric loads
• total power for mid-size car  3.5 kW
• different duty-cycle properties
(continuous, prolonged and sporadic)
http://www.eetimes.com/document.asp?doc_id=1272772

SistemasAutomóveis
Charging System: battery
• Typical battery internal resistance characteristic:
https://autoelectricalsystems.wordpress.com/page/6/
Engine
cranking
Ri = U/ I = 4/220 ≈ 18 mΩ

SistemasAutomóveis
Alternator: operational characteristics
• Typical current vs RPM output of a car alternator
• current/power grows with RPM (overdamped behavior)
• typically, alternator rotates 2-4 faster than engine
• current/power drops with alternator temperature increase
http://www.pirate4x4.com/tech/billavista/Wiring/Part2/
http://www.agcoauto.com/content/news/p2_articleid/348

SistemasAutomóveis
• Typical voltage vs current output of a car alternator
• voltage drops with current increase (abruptly above nominal current)
http://www.aturnofthenut.com/2016/02/11/alternators-with-multiple-battery-banks/

SistemasAutomóveis
• Typical power efficiency vs RPM
• efficiency decreases with RPM increase
http://www.intechopen.com/books/new-advances-in-vehicular-technology-and-automotive-
engineering/power-electronic-solutions-to-improve-the-performance-of-lundell-automotive-alternators

SistemasAutomóveis
• Power efficiency is affected by
• Mechanical losses
• brush and bearing friction
• claw pole rotor and cooling fan
• Electrical losses
• stator and rotor wirings
• regulator and rectifier
• Magnetic losses
• stator and rotor windings
http://www.intechopen.com/books/new-advances-in-vehicular-technology-and-automotive-
engineering/power-electronic-solutions-to-improve-the-performance-of-lundell-automotive-alternators
RPM 1800 6000
Mechanical losses 2% 6%
Excitation losses (rotor) 7% 3%
Magnetic losses (stator) 21% 20%
Copper losses (stator) 49% 57%
power rectifier losses 21% 14%

SistemasAutomóveis
Alternator: evolution
• From the dynamo to SOTA alternators
• more power, efficiency and reliability
• less noise and vibration
http://www.autoserviceprofessional.com/article/94748/alternator-decouplers-servicing-these-vibration-
reducing-pulleys

SistemasAutomóveis
Alternator: manufacturers
• Car alternator manufacturers
• Denso
• Bosch
• Valeo
• Remy
• Hella
• ISKRA
• Mando
• Mitsubishi
• Hitachi
• Magneti Marelli
• …
https://www.newswire.com/press-release/car-alternator-market-global-technical-data-and-growth-2020

SistemasAutomóveis
Alternator: types
• Alternators can be mainly classified according to the type of
magnetic excitation/inductor (in the rotor)
• permanent magnets (brushless alternator) – left
• electromagnets (field coil) – right
http://www.windbluepower.com/Permanent_Magnet_Alternator_Rotor_Fits_Delco_10SI_p/pma-rot.htm
http://mechanics.stackexchange.com/questions/25635/what-are-slip-rings-with-respect-to-a-cars-alternator

SistemasAutomóveis
Alternator: electromagnet inductor type
• Main components and assembly
http://de.bosch-
automotive.com/en/parts_and_accessories/motor_and_sytems/starters_alternators_1/alternators_for_cars_1/starters_alternators_alternators

SistemasAutomóveis
• Components and assembly
1. Drive pulley
2. Rotor
3. Slip ring
4. Rotor windings
5. Stator + windings
6. Rectifier
7. Output connector
8. Field diodes
9. Voltage regulator
10. Brush assembly
11. Fan
11

SistemasAutomóveis
• Basic circuit (Y stator, 9 diodes, integrated regulator)
https://www.alternatorparts.com/understanding-alternators.html
This block
does not exist
in brushless
alternators

SistemasAutomóveis
• Rotor (inductor)
• regulator feeds DC current to field coil through
brushes-slip rings contact
• typically 6 or 8 N/S pole pairs (12 or 16 poles)
6 pole pairs
8 pole pairs

SistemasAutomóveis
• alternating N/S poles in polar “fingers/claws”
• induce EMF in the stator windings
http://autosystempro.com/tag/generators/

SistemasAutomóveis
• Slip rings in more compact alternators (e.g. motorcycles) can
also be perpendicular to the alternator shaft
http://www.ebay.com/bhp/cb650-rotor

SistemasAutomóveis
• Stator + rotor layout
• EMF must be additive, in all coils of a phase winding
http://www.pangolin.co.nz/node/16
…

SistemasAutomóveis
• Stator wiring configurations
• always 3-phase, Y (wye) or  (delta) wiring
• usually 6 or 12 coils per phase (18 or 36 coils total)
http://www.instructables.com/id/How-To-Rewind-an-Alternator/step3/Star-or-Delta-windings/

SistemasAutomóveis
• Brushes + slip rings
• each brush connects to one slip ring
• one brush is + and the other is –
• the slip rings are electrically connected to the field coil terminals
• regulator controls excitation through ON/OFF control
http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/753046-alternator-question.html
http://www.allaboutcircuits.com/textbook/experiments/chpt-4/automotive-alternator/

SistemasAutomóveis
• Rectifier (diode) bridge
• 3-phase bridge based on passive elements (diodes)
• brushless alternator has a different rectifier principle!
• Typical rectifier assembly designs and mounting
http://www.asia.ru/ru/ProductInfo/891739.html

SistemasAutomóveis
• Diode types
• “Phase” diodes – full wave rectification of the 3 phases
• 6 power diodes (minimum configuration)
• 3 + and 3 – power diodes (2 diodes per phase)
• for electrical power-hungry vehicles, each phase has 4 diodes
• “Neutral” diodes – full-wave rectification of the neutral
• 2 diodes connected to the neutral point (only for Y wiring)
• induced third harmonic voltage increases output current/power
at high RPMs (> 2000-3000)  5-10% extra output power
• can be used for B+ or to feed the regulator/field coil
• “Field” diodes (AKA as excitation diodes or diode trio)
• 3 diodes (connected to the phases) feed the field coil
• half-wave rectification (it is sufficient for the field coil)
Bosch Automotive Electrics and Automotive Electronics: Systems and Components, Networking and Hybrid Drive, Edition 5, 2013
http://youronlinemechanic.com/alternator-with-neutral-point-voltage/

SistemasAutomóveis
• Bridge configurations (combinations of the previous)
• 6 power diodes (minimum configuration)
• 3 + and 3 – power diodes (2 per phase)
• 8 power diodes
• 6 power diodes
• 2 diodes for the neutral
• 9 diodes
• 6 power diodes
• 3 field diodes
• 11 diodes
• 8 power diodes
• 3 field diodes
• 17 diodes
• 12 power diodes (4 per phase)
• 2 diodes for neutral
• 3 field diodes
…
http://youronlinemechanic.com/alternator-with-neutral-point-voltage/

SistemasAutomóveis
• 6-diodes bridge
http://forums.off-road.com/jeep-short-wheelbase/276087-alternator-based-board-welders-set-me-straight.html
…

SistemasAutomóveis
• 8-diodes bridge
http://www.wiringdiagrams21.com/2013/03/04/suzuki-4x4-sj413-alternator-and-charging-system-circuit/
http://www.google.com/patents/US6828703

SistemasAutomóveis
• 9-diodes bridge
https://www.alternatorparts.com/understanding-alternators.html

SistemasAutomóveis
• 11-diodes bridge
http://xwebforums.org/showthread.php?t=16065&page=2

SistemasAutomóveis
• 17-diodes bridge (for high power requirements)
Bosch Automotive Electrics and Automotive Electronics: Systems and Components,
Networking and Hybrid Drive, 5th Edition, 2013

SistemasAutomóveis
• Voltage Regulator
• Guarantees a steady DC voltage output regardless of the RPM
• “senses” output voltage
• should be around 14.5 V
• controls the excitation of the alternator
• field coil current (ON/OFF)
• ON  EMF induction
• OFF  no induction
https://en.wikipedia.org/wiki/Voltage_regulator
…
Regulator acts as
an on/off switch
Switching
duty-cycle
influences
output voltage

SistemasAutomóveis
• Voltage Regulator
• switching can be on the positive or negative side of the field coil
http://www.pangolin.co.nz/node/16

SistemasAutomóveis
• Voltage Regulator operating principle
• Electromechanical (until the 60s)
• based on electromechanical relays
• Electronic (60s to 90s)
• based on discrete or integrated electronic circuits
• ECU-controlled (90s to date)
• sensing, computation, actuation
• optimizes alternator (regulator) output voltage and
alternator torque, depending on several operating conditions
• protects battery and optimizes fuel consumption/exhaust
gas emissions
…

SistemasAutomóveis
• Mechanical Regulator
• basic operating principle
…

SistemasAutomóveis
• Electronic Regulator (MOSFET-based)
http://chemelec.com/Projects/Alternator/Alternator-Reg.htm
…

SistemasAutomóveis
• Electronic Regulator (bipolar transistor-based)
http://chemelec.com/Projects/Alternator/Alternator-Reg.htm
…

SistemasAutomóveis
• Electronic Regulator (IC-based)
• control section, power stage, fault
diagnosis (controls warning lamp) and
protection against short circuits.
http://img.radiokot.ru/files/104594/medium/pr2p35jk0.JPG
http://circuitswiring.com/l9407f-car-alternator-voltage-regulator-datasheet/

SistemasAutomóveis
https://autoelectricalsystems.wordpress.com/page/6/
• ECU-controlled regulator (aka smart charging)
• controls changing rate based on electrical requirements,
battery/ambient temperature, and several other inputs
• reduces fuel consumption (reducing alternator load on ICE)
• optimizes & protects the battery
Powertrain Control
Module (engine ECU)

SistemasAutomóveis
http://www.embedded.com/design/real-time-and-performance/4006472/Designing-
a-microcontroller-driven-alternator-voltage-regulator
• ECU-controlled regulator (thermal compensation)
• warm batteries are more efficiently charged with low voltage
and cold batteries with higher voltage
• ECU adapts charge voltage depending on battery temperature
• battery temperature estimated by intake air + water temperatures
• battery charging is optimized through real-time adjustment of
the alternator output voltage

SistemasAutomóveis
http://www.hella.com/startersalternators/assets/media/g06_ti_en_electronics_ford_smart_charge_system.pdf
• ECU-controlled regulator (alternator switch-off and ISC)
• Alternator switch-off when cranking the engine
• when the engine is started, the alternator is deactivated by
the PCM to reduce the engine drag torque
• the alternator is only switched on to the required value by
the PCM after the engine has been started up
• Engine idle speed control (ISC), depending on electrical load
demand and system voltage
• the PCM can increase the charge current by changing the
pulse-width modulated signal to the alternator
• when the electrical load (in idling) is very high
• when the vehicle electric system voltage is very low
(e.g. low battery charge)

SistemasAutomóveis
http://www.hella.com/startersalternators/assets/media/g06_ti_en_electronics_ford_smart_charge_system.pdf
• ECU-controlled regulator (consumers switch on/off)
• consumers are activated or deactivated in the event of
overvoltage or undervoltage (depending on electrical system
voltage variations), e.g. :
• air conditioning system
• heated windscreen
• heated rear window

SistemasAutomóveis
http://www.automotive-eetimes.com/content/reduce-vehicle-power-consumption-and-
increase-efficiency-start-charging-system/page/0/1
• ECU-controlled regulator (Freescale)
• charging system ↔ ECU comm via LIN (control & diagnostic)
• Mechanical, Electrical, Thermal, Comm. Fault detection

SistemasAutomóveis
http://www.automotive-eetimes.com/content/reduce-vehicle-power-consumption-and-
increase-efficiency-start-charging-system/page/0/1
• ECU-controlled Regulator (EXAMPLE 2)
• …

SistemasAutomóveis
Alternator: permanent magnet inductor type
• Differences to electromagnet inductor alternators
• inductor (rotor) is made of permanent magnets
• does not have a field coil, brushes nor slip rings
• thus, voltage regulation cannot be performed in the same way
• because there is no control over the inductor magnetic field
• voltage regulation is performed by controlling the power output
• via a silicon controlled rectifier (SCR)
• Types
• Inner inductor/rotor
• outer inductor/rotor
http://www.five-gallon-bucket-hydroelectric.org/the-new-toyota-alternator-pma-for-the-generator/
…

SistemasAutomóveis
• Inner inductor permanent magnet alternator
• rotor rotates inside the stator
https://www.comsol.com/blogs/simulating-permanent-
magnet-generators/

SistemasAutomóveis
• stator, rotor and regulator (left) and full assembly (right)
http://roadandrace.com.au/alternator_conversions.htm
http://cybermotorcycle.com/archives/willyg/index.html

SistemasAutomóveis
• alternator mounted in a motorcycle
http://ebw.co.in/tag/adventure/

SistemasAutomóveis
• Outer inductor permanent magnet alternator
• rotor outside the stator, incorporated in the flywheel
• magnets are located radially in the flywheel (made of steel)
• Advantages:
• the magnetic properties of the steel enhance the magnetic
field and increase coil current;
• magnetic attraction to the steel and centrifugal force help to
keep the magnets in position
• the weight of the magnets increase the flywheel weight
(inertial mass)

SistemasAutomóveis
• rotor outside the stator, incorporated in the flywheel
• magnets are located radially in the flywheel (made of steel)
http://www.bikesandtravels.com/biker.aspx?ride=730
Flywheel Stator

SistemasAutomóveis
• Advantages:
• the magnetic properties of the steel enhance the magnetic
field and increase coil current;
• magnetic attraction to the steel and centrifugal force help to
keep the magnets in position
• the weight of the magnets increase the flywheel weight
(inertial mass)

SistemasAutomóveis
• Rotor mounted with flywheel gear (left)
• Stator mounted in engine case (right)
http://www.homemodelenginemachinist.com/showthread.php?t=14129

SistemasAutomóveis
• Voltage Regulation
• shunt-type: short-circuits output current to ground
• series-type: output current is switched ON/OFF
http://www.radio-electronics.com/info/power-management/linear-power-supply-psu/series-voltage-regulator-theory-circuit.php
Shunt-type Series-type
http://www.radio-electronics.com/info/power-management/linear-power-supply-psu/shunt-voltage-regulator-theory-circuit.php

SistemasAutomóveis
• Voltage Regulation – shunt-type
• short-circuits output current to ground, to regulate voltage
Single phase
Three phase
http://racetechelectric.com/ft-751-voltage-regulators.html

SistemasAutomóveis
• shunts performed by thyristors (gate controlled by a Zener)
http://www.microchip.com/forums/m350762.aspx

SistemasAutomóveis
• another configuration
http://mastercircuits.blogspot.pt/2010/05/motorcycle-voltage-regulator.html

SistemasAutomóveis
• shunts performed by thyristors (gate controlled by IC)
http://www.eevblog.com/forum/projects/car-alternators-vs-motorcycle-alternators/

SistemasAutomóveis
• for a single phase alternator
http://mastercircuits.blogspot.pt/2010/11/single-phase-voltage-regulator.html

SistemasAutomóveis
• Voltage Regulation – series-type
• output current is switched ON/OFF
• basic design:
http://www.circuitstoday.com/voltage-regulators

SistemasAutomóveis
• Voltage Regulation – series-type
• real implementation:
http://mastercircuits.blogspot.pt/2013/09/3-phase-voltage-regulator-series-type.html
Generator
+ rectifier
Electronic
relay
Voltage sensing and
relay controller

SistemasAutomóveis
• Voltage Regulation – fully-controlled rectification
• não encontrei nada aplicado à rectificação/regulação de
alternadores de ímanes permanentes com pontes rectificadoras
controladas (transistores, MOSFETs, tiristores)
http://i444.photobucket.com/albums/qq167/rjdoles/regulatorschematicdiagram.jpg
http://www.electrosport.com/technical-resources/technical-articles/how-motorcycle-charging-system-works

SistemasAutomóveis
Alternator: cooling
• Cooling
• air-cooled
• water-cooled
• oil-cooled
http://www.electronics-cooling.com/2002/05/thermal-design-challenges-in-automotive-alternator-power-electronics/
http://www.delcoremy.com/alternators/find-by-model-family/50dn-plus/
http://www.4-wheeling-in-western-australia.com/toyota-70-series.html
Oil-cooled
(450 A brushless)
Air-cooled
Water-cooled

SistemasAutomóveis
Technology trends
• Overrunning Alternator Decoupler (OADs) pulley
• helps "synchronize" the belt drive system for improved engine
efficiency, reduced noise and vibration and increased lifetime
• when RPM increases, the alternator's inertia creates resistance
against the belt (alternator typically rotates 3x faster than engine)
• these factors often cause "rope-tow effect" in which belt and
alternator speeds are out of phase; belt tensioners can absorb some
of the resulting vibration, but the belt is affected by these forces
• an OAD pulley has an internal spring and clutch system that absorbs
the force associated with belt accelerations and tension
reversals and permits the alternator to "free-wheel"
or "overrun" when the belt suddenly decelerates.
http://www.decouplerpulley.com/
https://youtu.be/jKMf-_Yl-AI

SistemasAutomóveis
Technology trends
• Intelligent Alternator Control with regenerative braking
• generates electric power during
• overrun (drive phases in which the engine is not required to deliver
drive power)
• Braking (while the driver is applying the brakes)
• battery is charged to only about 80% of its capacity as long as the engine is
propelling the car
• battery charge exceeding the 80% threshold is generated only in overrun and
braking
• Advantages
• less fuel consumption (≈ 3%)
• more available (engine) power during acceleration (alternator is
disconnected whenever the engine is propelling the car)
http://www.greencarcongress.com/2006/09/bmw_introduces_.html

SistemasAutomóveis
Glossary (English/Portuguese)
• …

SistemasAutomóveis
Recommended references
• http://www.circuitstoday.com/voltage-regulators

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