1 Image courtesy of Tesla Corp. Electric Motors for Electric
cars and Hybrids
Slide 2
2 High Voltage Safety Contact with voltage of less than 50
volts is unlikely to cause injury. Voltages above 50 volts are
potentially deadly. Anytime you work on and around electrical
systems that have voltages above 50 volts proper safety procedures
must be observed to avoid injury. Contact with voltage of less than
50 volts is unlikely to cause injury. Voltages above 50 volts are
potentially deadly. Anytime you work on and around electrical
systems that have voltages above 50 volts proper safety procedures
must be observed to avoid injury. Danger High Voltage
Slide 3
3 High Voltage Safety Its not the voltage that kills its the
current [Amps] The human body conducts electricity when the voltage
is increased, the amount of current passing through the body
increases proportionally Its not the voltage that kills its the
current [Amps] The human body conducts electricity when the voltage
is increased, the amount of current passing through the body
increases proportionally High Voltage
Slide 4
4 High Voltage Safety 1 milliamp slight tingle 5 milliamps mild
shock not painful 6 to 30 milliamps painful shock muscle control is
lost 50 to 150 milliamps extreme pain respiratory arrest - you cant
let go of anything in your grasp potentially fatal 1 to 4.3 amps
ventricular fibrillation [heart attack] nerve damage probably fatal
10 amps Cardiac arrest Severe burns Electrocution 1 milliamp slight
tingle 5 milliamps mild shock not painful 6 to 30 milliamps painful
shock muscle control is lost 50 to 150 milliamps extreme pain
respiratory arrest - you cant let go of anything in your grasp
potentially fatal 1 to 4.3 amps ventricular fibrillation [heart
attack] nerve damage probably fatal 10 amps Cardiac arrest Severe
burns Electrocution
Slide 5
5 High Voltage Safety Orange wires contain high voltage
conductors. Before doing any work that requires disconnecting an
orange cable the service plug must be removed. Orange wires contain
high voltage conductors. Before doing any work that requires
disconnecting an orange cable the service plug must be
removed.
Slide 6
6 Inverter Capacitors can Kill The Inverter contains 3 large
capacitors that can hold a charge for up to 5 minutes after the
service plug is removed Wait at least 5 minutes before beginning
work The Inverter contains 3 large capacitors that can hold a
charge for up to 5 minutes after the service plug is removed Wait
at least 5 minutes before beginning work Drain Resistor
Slide 7
7 Class 0 Gloves High voltage rubber gloves with leather covers
are required when working on BEV and Hybrid vehicles
Slide 8
8 CAT III DVOM A CAT III rated meter with CAT III rated test
leads is needed when working on any high voltage automotive
system
Slide 9
9 Remove service plug The service plug disconnects the high
voltage battery array from the inverter when removed When working
on a high voltage system put the service plug in your toolbox so
that a coworker cannot reinstall it to move the vehicle The service
plug disconnects the high voltage battery array from the inverter
when removed When working on a high voltage system put the service
plug in your toolbox so that a coworker cannot reinstall it to move
the vehicle
Slide 10
10 Electric Traction Motors Electric motors are very compact
and are highly efficient Image courtesy of Robert Bosch GMBH Image
courtesy of Tesla Corp. A typical gasoline ICE engine has an
efficiency rating of a little over 25% Electric motors typically
operate between 95% to 98% efficiency A typical gasoline ICE engine
has an efficiency rating of a little over 25% Electric motors
typically operate between 95% to 98% efficiency 3 phase electrical
terminals Drive spline Resolver terminals Coolant tubes
Slide 11
11 Torque - Electric vs. ICE 100002000300040005000 100 lbs/ft
Electric Motor ICE Motor 200 6000 RPM An electric motor can produce
torque at 0 RPM and its torque output remains nearly constant up to
about 5000 rpm Because it produces constant torque at nearly all
RPMs electric cars do not require multiple speed transmissions
Slide 12
12 Motor generators The electric motor used to power a BEV or
hybrid also functions as a generator When the brakes are applied
the electric motor becomes a generator that converts the kinetic
energy of the vehicle into electricity that is then stored in the
battery This process is called regenerative braking Hybrid vehicles
also generate electricity when the ICE engine is running and the
batteries are discharged The electric motor used to power a BEV or
hybrid also functions as a generator When the brakes are applied
the electric motor becomes a generator that converts the kinetic
energy of the vehicle into electricity that is then stored in the
battery This process is called regenerative braking Hybrid vehicles
also generate electricity when the ICE engine is running and the
batteries are discharged
Slide 13
13 3 Types of Electric Motor Generators Inductive Brush type
Permanent Magnet Used only by Tesla and Toyota RAV-4 EV Not
suitable for electric vehicles Used by all manufactures except
Tesla Image courtesy of General Motors Corp.
Slide 14
14 Brush type electric motors Nearly all of the DC motors used
in non-hybrid automobiles use electric motors similar to starter
motors A set of graphite brushes conduct electricity to the
armature windings at the commutator Brushes are located deep inside
the motor and require periodic replacement This type of motor is an
efficient motor but it makes a very poor generator Nearly all of
the DC motors used in non-hybrid automobiles use electric motors
similar to starter motors A set of graphite brushes conduct
electricity to the armature windings at the commutator Brushes are
located deep inside the motor and require periodic replacement This
type of motor is an efficient motor but it makes a very poor
generator Stationary field coil Rotating Armature Brush Commutator
Power +
Slide 15
15 Brushless motors BEV and Hybrid vehicles use 3 phase AC
brushless motors There are two types: Permanent Magnet Inductive
Nearly all manufactures use the permanent magnet type All Tesla
vehicles use the Inductive type The Toyota RAV-4 EV uses an
electric driveline/battery system built by Tesla so it also has in
inductive motor BEV and Hybrid vehicles use 3 phase AC brushless
motors There are two types: Permanent Magnet Inductive Nearly all
manufactures use the permanent magnet type All Tesla vehicles use
the Inductive type The Toyota RAV-4 EV uses an electric
driveline/battery system built by Tesla so it also has in inductive
motor
Slide 16
16 Permanent magnet motors Image courtesy of General Motors
Corp
Slide 17
17 Permanent magnet rotor Instead of an armature the permanent
magnet motor has a rotor with 6, 8, 12 or 16 or more permanent
magnets attached to its outer circumference N S N S N S N S N S N
S
Slide 18
18 Permanent rare earth magnets The permanent magnets are made
of iron alloyed with small amounts of rare earth materials such
neodymium or samariumcobalt mixed with boron 2.2 pounds of
neodymium are used in the manufacture of every Toyota Prius The
permanent magnets are made of iron alloyed with small amounts of
rare earth materials such neodymium or samariumcobalt mixed with
boron 2.2 pounds of neodymium are used in the manufacture of every
Toyota Prius
Slide 19
19 Permanent Magnet Motor The magnets are normally encased in a
non-magnetic metal shell to prevent the them from being ripped out
of the rotor by centrifugal force at high RPM Image courtesy of
General Motors Corp
Slide 20
20 Stator coil The permanent magnet rotor is located inside a
stator coil The stator coil is a stationary set of electromagnets
that surrounds the rotor The stators three electromagnetic coils
windings are connected to an inverter The inverter is a series of
solid state switches that connects the stator coils to the high
voltage battery terminals as needed The permanent magnet rotor is
located inside a stator coil The stator coil is a stationary set of
electromagnets that surrounds the rotor The stators three
electromagnetic coils windings are connected to an inverter The
inverter is a series of solid state switches that connects the
stator coils to the high voltage battery terminals as needed To
inverter
Slide 21
21 Induction motors Image courtesy of General Motors Corp
Slide 22
22 Inductive Motors Inductive motors have a squirrel cage type
rotor Copper or aluminum [non magnetic materials] bars are mounted
between two rings. Instead of running parallel to the motor shaft
they are skewed slightly Inductive motors have a squirrel cage type
rotor Copper or aluminum [non magnetic materials] bars are mounted
between two rings. Instead of running parallel to the motor shaft
they are skewed slightly Copper or aluminum bars
Slide 23
23 Rotor for inductive motor The conductor bars are supported
by laminated iron plates that intensify the magnetic fields
Conductor bars
Slide 24
24 Inductive motor The stator coils magnetic field induces an
electric current into the copper strips on the conductor The
electric current will in turn have its own magnetic field
surrounding it The magnetic field surrounding the copper strip is
repelled from the stators magnetic field causing the rotor to turn
away from the stator coil The stator coils magnetic field induces
an electric current into the copper strips on the conductor The
electric current will in turn have its own magnetic field
surrounding it The magnetic field surrounding the copper strip is
repelled from the stators magnetic field causing the rotor to turn
away from the stator coil + -
Slide 25
25 Stators for inductive motors The Tesla BEV is designed for a
top speed of 130 mph so inductive motors were chosen for their high
speed advantage The inductive motor was invented by Nickolas Tesla,
hence the name of the car company The Tesla BEV is designed for a
top speed of 130 mph so inductive motors were chosen for their high
speed advantage The inductive motor was invented by Nickolas Tesla,
hence the name of the car company The stator coils for inductive
are almost identical to the stator coils in permanent magnet type
motors They generally have thicker wires and the wires are often
square in cross section to allow more current flow Inductive motors
are generally less efficient than permanent magnet motors at low
rpm and more efficient at high rpm The stator coils for inductive
are almost identical to the stator coils in permanent magnet type
motors They generally have thicker wires and the wires are often
square in cross section to allow more current flow Inductive motors
are generally less efficient than permanent magnet motors at low
rpm and more efficient at high rpm Cooling fins Image courtesy
Tesla corp.
Slide 26
26 Stator Assembly The stator coils are wrapped around a
laminated iron frame The stator assembly is nearly identical in
construction to a conventional alternator stator The power
requirements of the traction motor require the stator assembly to
be larger and wider The stator coils are wrapped around a laminated
iron frame The stator assembly is nearly identical in construction
to a conventional alternator stator The power requirements of the
traction motor require the stator assembly to be larger and
wider
Slide 27
27 Stator windings If the stator windings were removed from the
stator frame and then flattened out they would look like this U V
W
Slide 28
28 Stator windings Each winding is offset 20 from its neighbor
in a 6 pole motor Each winding is called a phase The 3 phases are
labeled U, V and W Each winding is offset 20 from its neighbor in a
6 pole motor Each winding is called a phase The 3 phases are
labeled U, V and W U V W U V W
Slide 29
29 Stator coil The each branch is wrapped around laminated iron
poles The stator coil is made up of 3 interconnected windings
[Phases] U V W 6 poles This stator has six poles but there can be
many more
Slide 30
30 Stator coil If a positive voltage is applied to the V
terminal and negative is applied to W, the poles shown here in blue
become magnetized with the north pole toward the center and the
yellow poles are magnetized with the south pole toward the center U
V + - S N N W N S S N S N S N N S N N S S N S S N N S S
Slide 31
31 Stator coil When you change the positive voltage to the U
terminal and negative is applied to the V, the poles shown here in
green become magnetized with the north pole toward the center and
the blue poles are magnetized with the south pole toward the center
U V + - W S N N N S S N S N S N N S N N S S N S S N N S S
Slide 32
32 Stator coil When positive voltage is applied to the W
terminal and negative is the U, the poles shown here in yellow
become magnetized with the north pole toward the center and the
green poles are magnetized with the south pole toward the center U
V + - W S N N N S S N S N S N N S N N S S N S S N N S S
Slide 33
33 Permanent magnet rotor The rotor is attached the motor shaft
and has a set of permanent magnets embedded near the outer
circumference N S N S N S N S N S N S
Slide 34
34 Rotor with permanent magnets The rotor has a set of
permanent magnets bonded to an iron disc In some designs two
permanent magnets are arraigned in a V The rotor has a set of
permanent magnets bonded to an iron disc In some designs two
permanent magnets are arraigned in a V
Slide 35
35 Magnetic field surrounding the rotor Lines of magnetic force
extend outward from the rotor The magnets will be attracted to
stator poles with the opposite polarity and repelled from stator
poles with the same polarity Lines of magnetic force extend outward
from the rotor The magnets will be attracted to stator poles with
the opposite polarity and repelled from stator poles with the same
polarity NS
Slide 36
36 Motor operation When the stator coils are energized the
north poles on the rotor will be attracted to the stators south
poles and repelled from the north poles Red = North Pole [inside]
Green = South Pole Blue = not Magnetized + - U V W
Slide 37
37 Motor operation For rotation to continue the polarity of the
stator coils must change By applying + positive voltage to terminal
V and negative to terminal W the stator poles move 20 counter
clockwise For rotation to continue the polarity of the stator coils
must change By applying + positive voltage to terminal V and
negative to terminal W the stator poles move 20 counter clockwise
Red = North Pole [inside] Green = South Pole Blue = not Magnetized
+ - U V W
Slide 38
38 Motor operation Changing the polarity of the stator coils by
changing the electrical polarity at the stator terminals will cause
the rotor to move another 20 counterclockwise Red = North Pole
[inside] Green = South Pole Blue = not Magnetized + U V W -
Slide 39
39 Motor operation Continuously alternating the polarity of the
voltage applied to the stator terminals will produce a rotating
magnetic field that will drive the rotor and apply torque to the
drive wheels Red = North Pole [inside] + U V W - + - + -
Slide 40
40 Generator Operation The rotor is surrounded by intense
magnetic fields.
Slide 41
41 Generator Operation When lines of magnetic force move
through a conductor an electric current is induced in the conductor
When the lines of magnetic force are approaching the conductor the
electrons flow in one direction When the lines of magnetic force
move away from the conductor the electrons move in the opposite
direction When lines of magnetic force move through a conductor an
electric current is induced in the conductor When the lines of
magnetic force are approaching the conductor the electrons flow in
one direction When the lines of magnetic force move away from the
conductor the electrons move in the opposite direction A rotating
magnetic field will produce an AC current in the conductor as the
field moves toward and away from the conductor
Slide 42
42 Generator Operation during braking The inverter converts
this AC current to DC and sends it back to the HV batteries The
current flowing through the stator windings has its own magnetic
field The magnetic field created by current flowing through the
stator windings repels the magnetic field of the rotor magnets The
inverter converts this AC current to DC and sends it back to the HV
batteries The current flowing through the stator windings has its
own magnetic field The magnetic field created by current flowing
through the stator windings repels the magnetic field of the rotor
magnets This magnetic repulsion puts a load [drag] on the rotor
that causes the vehicle to slow down
Slide 43
43 Generator Operation When the batteries are maximum charge
[80% SOC] the inverter will the shut down the flow of current to
the batteries. With no current flowing through the stator windings
there will be no magnetic resistance applied to the rotor When the
batteries are maximum charge [80% SOC] the inverter will the shut
down the flow of current to the batteries. With no current flowing
through the stator windings there will be no magnetic resistance
applied to the rotor The hydraulic brakes will be needed to slow
the vehicle when the batteries are fully charged No current
flow
Slide 44
44 Hybrid motor location There are three locations for hybrid
electric motor[s] BAS [Belt-Alternator-Starter] hybrid systems have
a small electric motor / generator bolted to the engine in place of
an alternator IMA systems have a single motor / generator
sandwiched between the engine and the transmission Two motor
hybrids have 2 motor /generators located inside the transmission
There are three locations for hybrid electric motor[s] BAS
[Belt-Alternator-Starter] hybrid systems have a small electric
motor / generator bolted to the engine in place of an alternator
IMA systems have a single motor / generator sandwiched between the
engine and the transmission Two motor hybrids have 2 motor
/generators located inside the transmission
Slide 45
45 BAS Systems The GM BAS [Belt- Alternator-Starter] system
uses an intermediate voltage motor [42 volts] that is driven by the
multi-rib belt The hybrid motor supplies additional torque to the
crankshaft when operating under load and functions as a starter
during start-stop operation The GM BAS [Belt- Alternator-Starter]
system uses an intermediate voltage motor [42 volts] that is driven
by the multi-rib belt The hybrid motor supplies additional torque
to the crankshaft when operating under load and functions as a
starter during start-stop operation Image courtesy of General
Motors Corp Note: three phase AC cables are not orange 42 volts max
Motor / Generator
Slide 46
46 IMA type motor location Honda introduced the IMA [Integrated
Motor Assist] on the 1999 Insight. The IMA motor is sandwiched
between the back of the engine block and the transmission case
Stator windings Rotor CVT Transmission
Slide 47
47 Honda IMA Motor Since the stator assembly is bolted directly
to the engine block heat is removed through the engine cooling
jackets Image courtesy American Honda Motor Corp Stator windings
Rotor U, V & W electrical cables
Slide 48
48 The rotor in the IMA system is bolted directly to the
crankshaft The flywheel and damper assembly is bolted to the rotor
The rotor in the IMA system is bolted directly to the crankshaft
The flywheel and damper assembly is bolted to the rotor Rotor
location Stator windings Rotor
Slide 49
49 Stator and Rotor Assembly Porsche also uses an IMA system
where the rotor attached to the crankshaft. The stator coils are
cooled by engine coolant Coolant Inlet Coolant Outlet Image
courtesy of Robert Bosch GMBH Stator Leads
Slide 50
50 This special tool is needed to remove the Honda rotor from
the crankshaft The rotor must be removed to service the rear main
seal This special tool is needed to remove the Honda rotor from the
crankshaft The rotor must be removed to service the rear main seal
Rotor removal
Slide 51
51 Rotor storage The permanent magnets on the rotor are so
powerful it can cause injury if your fingers were to get caught
between the rotor and a steel work bench or vise It takes about 100
pounds of pulling force to lift the rotor shown here away from the
vice The permanent magnets on the rotor are so powerful it can
cause injury if your fingers were to get caught between the rotor
and a steel work bench or vise It takes about 100 pounds of pulling
force to lift the rotor shown here away from the vice Honda rotor
removal/installation tool
Slide 52
52 IMA System limitations The problem with the IMA system is
that the crankshaft of the ICE engine is directly coupled to the
electric motor This prevents the vehicle from running in electric
mode This limits the efficiency of the system as the engine must
always be running when the vehicle is in motion The problem with
the IMA system is that the crankshaft of the ICE engine is directly
coupled to the electric motor This prevents the vehicle from
running in electric mode This limits the efficiency of the system
as the engine must always be running when the vehicle is in motion
Image courtesy of Robert Bosch GMBH
Slide 53
53 Two motor Single Mode Toyota, Ford and Nissan hybrids use
two electric motors located inside the transmission MG2 MG1
Planetary gearset
Slide 54
54 Motor / Generators for Prius By placing 2 electric motors
inside the transmission the vehicle can be driven solely by
electric power at road speeds up to 30 MPH The planetary gearset
allows the torque from the ICE engine to be combined with the
torque of the two electric motors Having two electric motors allows
the transmission to operate as a CVT By placing 2 electric motors
inside the transmission the vehicle can be driven solely by
electric power at road speeds up to 30 MPH The planetary gearset
allows the torque from the ICE engine to be combined with the
torque of the two electric motors Having two electric motors allows
the transmission to operate as a CVT Image courtesy of Toyota
Motors Corp MG1 MG2 Planetary gearset Stator temperature sensor
connector
Slide 55
55 Electric motors located inside the transmission Coolant
passages inside the transmission case remove excess heat from the
stator coils The stator windings and rotor are exposed to
transmission fluid Oil pickup tube
Slide 56
56 Dual mode transmissions also have two traction motors Dual
mode transmissions The dual mode transmission also has conventional
clutches that allow engine torque to be applied directly to the
drive wheels at highway speeds Rotor for Motor #2 Rotor for Motor
#1 Image courtesy of General Motors Corp Electric oil pump Clutch
packs
Slide 57
57 Dual mode transmission A dual mode system can run: Under
electric power with the ICE engine shut down Under a combination of
ICE and electric power Under mechanical drive with the electric
motors essentially shut down A dual mode system can run: Under
electric power with the ICE engine shut down Under a combination of
ICE and electric power Under mechanical drive with the electric
motors essentially shut down Motor #2 Motor #1 Clutch packs
Slide 58
58 Cooling electric motors Although the electric motor
[permanent magnet or inductive] is up to 98% efficient that 2% of
the electrical energy that is not converted to mechanical power is
converted into heat Excess heat is normally removed by a liquid
cooling system but some motors use air cooling Although the
electric motor [permanent magnet or inductive] is up to 98%
efficient that 2% of the electrical energy that is not converted to
mechanical power is converted into heat Excess heat is normally
removed by a liquid cooling system but some motors use air cooling
Coolant passage for MG2 Coolant passage for MG1
Slide 59
59 Prius coolant passages The Prius has coolant inlet and
outlet tubes for each of the electric motors inside the transaxle
Coolant inlet Coolant outlet
Slide 60
60 Liquid cooling systems Two motor hybrid systems use liquid
cooling systems to remove excess heat from the electric
motor/generator and inverter This cooling system is completely
separate from the ICE engines cooling system and has its own
radiator and water pump The high temperatures of the ICE cooling
system would damage the electronics inside the inverter Coolant is
long life antifreeze and water An electric water pump circulates
coolant through the inverter and motor generator housing
[transmission] Two motor hybrid systems use liquid cooling systems
to remove excess heat from the electric motor/generator and
inverter This cooling system is completely separate from the ICE
engines cooling system and has its own radiator and water pump The
high temperatures of the ICE cooling system would damage the
electronics inside the inverter Coolant is long life antifreeze and
water An electric water pump circulates coolant through the
inverter and motor generator housing [transmission]
Slide 61
61 Two coolant reservoirs Two motor hybrids have two coolant
reservoir tanks One for the ICE engine typically located an the
radiator support A second reservoir for the inverter is typically
bolted to the side of the inverter case A coolant level sensor is
located inside the reservoir for the inverter/motor Most
manufactures recommend that the fluid level in the inverter
reservoir should never be topped off Topping off the fluid level
will mask a slow leak in the system preventing the warning light
from turning on Two motor hybrids have two coolant reservoir tanks
One for the ICE engine typically located an the radiator support A
second reservoir for the inverter is typically bolted to the side
of the inverter case A coolant level sensor is located inside the
reservoir for the inverter/motor Most manufactures recommend that
the fluid level in the inverter reservoir should never be topped
off Topping off the fluid level will mask a slow leak in the system
preventing the warning light from turning on
Slide 62
62 Two coolant reservoirs Reservoir for electric motors and
inverter Reservoir for ICE engine coolant
Slide 63
63 BEV motor cooling This Nissan Leaf traction motor has
cooling passages similar to an ICE engine Note the freeze out plugs
an the outside of the housing Coolant inlet Freeze-out plugs
Coolant outlet Bracket for A/C compressor
65 BEV Cooling System An electrically driven water pump
circulates coolant through the inverter, traction motor and
radiator. Inverter Motor Radiator Electric Water Pump To Batteries
The PCM monitors the motor temperature The PCM increases the water
pump speed as temperature increases
Slide 66
66 Electric Water Pump Pump speed can be controlled by the PCM
by pulse width modulation In a PWM system the computer varies the
on time vs. off time to control the flow of electrical current
through the motor The electric motors that drive the A/C compressor
will use a 3 phase permanent magnet motor whos speed is controlled
by an inverter
Slide 67
67 Resolver The Resolver is a sensor that sends rotor position
data to the Hybrid or EV control module Resolver coil Elliptical
disc
Slide 68
68 Resolver The PCM needs to know where the rotor is before it
can determine the proper stator phase coils to energize Unlike a
crankshaft position sensor that generates an electrical pulse as
the engine rotates the resolver can determine the position of the
rotor when the electric motor is not turning The PCM needs to know
where the rotor is before it can determine the proper stator phase
coils to energize Unlike a crankshaft position sensor that
generates an electrical pulse as the engine rotates the resolver
can determine the position of the rotor when the electric motor is
not turning
Slide 69
69 Resolver Circuit The resolver provides the Hybrid Control
Module with rotor position information Coil A Input Coil C Output
Coil B Output Elliptical disc on rotor Shaft AC Signal The AC
signal in coil A creates a pulsating magnetic field that is carried
into the resolver disc If the resolver disc is close to an output
coil a high amplitude return signal is sent back to the hybrid
control module The Hybrid Control Module compares the difference in
amplitude between coil B and coil C to determine the exact position
of the rotor
Slide 70
70 Prius resolver The Prius has two resolvers One for each
electric motor inside the transaxle The resolver is bolted to the
case cover and should never be removed Resolver timing is critical
resetting the resolver timing can only be done by the factory The
Prius has two resolvers One for each electric motor inside the
transaxle The resolver is bolted to the case cover and should never
be removed Resolver timing is critical resetting the resolver
timing can only be done by the factory Pigtail lead connects to
hybrid control module The resolver contains a set of three
electromagnetic coils
Slide 71
71 Prius resolver An eccentric disc is attached to the rotor
shaft This disc rotates inside the electromagnet coils in the
resolver An eccentric disc is attached to the rotor shaft This disc
rotates inside the electromagnet coils in the resolver Resolver
eccentric Rotor
Slide 72
72 Gear reduction units for BEVs Battery electric vehicles
require a gear reduction unit to reduce the speed produced by the
electric motor down to a speed that the wheels normally rotate
Electric motors produce nearly constant torque so a multi-speed
transmission is not needed At 60 MPH a 24 high tire [P 215 70 R 14]
is rotating at only 841 RPM The electric motor operates a peak
efficiency at speeds of 3500 to 5500 RPM Battery electric vehicles
require a gear reduction unit to reduce the speed produced by the
electric motor down to a speed that the wheels normally rotate
Electric motors produce nearly constant torque so a multi-speed
transmission is not needed At 60 MPH a 24 high tire [P 215 70 R 14]
is rotating at only 841 RPM The electric motor operates a peak
efficiency at speeds of 3500 to 5500 RPM Gear reduction unit Image
courtesy of Robert Bosch GMBH
Slide 73
73 Gear Reduction Units To bring the RPM of the electric motor
down to the speed that wheels turn in normal driving requires a
gear reduction of about 5 to 1 The gear reduction unit also
includes a differential gearset that allows the wheels on either
side of the vehicle to turn at different speeds To bring the RPM of
the electric motor down to the speed that wheels turn in normal
driving requires a gear reduction of about 5 to 1 The gear
reduction unit also includes a differential gearset that allows the
wheels on either side of the vehicle to turn at different speeds
Electric motor and gear reduction unit for Toyota Highlander
Hybrid
Slide 74
74 BEV Gear reduction unit Parking pawl actuator motor The gear
reduction unit shown here uses a conventional 2 stage spur type
gearset
Slide 75
75 Reduction gears Spur type reduction gears are used when the
electric motor is mounted ahead of or behind the axle centerline
Input = 22 Final drive = 62 Idler - driven = 32 Idler - driving =
20 First stage ratio = 32 22 = 1.64 Second stage ratio = 62 22 =
3.1 Overall gear ratio = 1.64 x 3.1 = 5.07
Slide 76
76 Gear reduction using Planetary gears If the traction motor
is to be located on the axle centerline a set of planetary gears is
used to provide gear reduction This helps place the weight of the
motor lower to the ground for better handling and allows for more
cabin room If the traction motor is to be located on the axle
centerline a set of planetary gears is used to provide gear
reduction This helps place the weight of the motor lower to the
ground for better handling and allows for more cabin room Image
courtesy of Robert Bosch GMBH Sun gear Planet gear Ring gear
Slide 77
77 Electric Motor/Transmission/Differential To help improve
efficiency at highway speeds a second electric motor can be coupled
to the primary motor to provide continuously variable gear ratios
[CVT] Primary electric motor CVT torque combining gearset Secondary
electric motor Planetary gearset type differential Image courtesy
FAG GMBH
Slide 78
78 Hub Mounted Motors Alternatively motors can be mounted in
the wheel hubs Motors larger than 20 KW generally require liquid
cooling Alternatively motors can be mounted in the wheel hubs
Motors larger than 20 KW generally require liquid cooling 3 Phase
AC Current Coolant Stator Rotor Mitsubishi BEV Hub Motor
Coolant
Slide 79
79 Hub Mounted Rotor Simplicity no gears, differentials or axle
shafts. Increases interior volume no engine compartment needed. In
four wheel drive configuration - allows regenerative braking from
all 4 wheels. Ideal power train for 4WD and automatic traction
control. Using differential power [More torque to one side]
eliminates the need for power steering. Simplicity no gears,
differentials or axle shafts. Increases interior volume no engine
compartment needed. In four wheel drive configuration - allows
regenerative braking from all 4 wheels. Ideal power train for 4WD
and automatic traction control. Using differential power [More
torque to one side] eliminates the need for power steering. Very
high unsprung weight has negative effect on handling. No torque
multiplication. If one motor fails the torque of the working motor
will create a severe torque steer condition. Difficult to cool.
Motor is exposed to dirt, water and vibration.
AdvantagesDisadvantages
Slide 80
80 Hub Motors Hondas Experimental Air Cooled Hub Motor Image
courtesy American Honda Motor Corp
Slide 81
81 Prototype Hub Motor Wheel Bearing Steering Knuckle Stator
Stator coils, power electronics and micro-inverter Rotor
Conventional alloy rim and tire Image courtesy Protean Corp
Slide 82
82 Service and repair The only service that the electric motor
requires is coolant replacement at typically 5 year / 100,000 mile
intervals There are very few replaceable parts Most manufacturers
will provide only remanufactured motor assemblies[BEV] or
transmissions Aftermarket remanufactured stator and rotor kits are
becoming available for the gen 2 & 3 Prius The only service
that the electric motor requires is coolant replacement at
typically 5 year / 100,000 mile intervals There are very few
replaceable parts Most manufacturers will provide only
remanufactured motor assemblies[BEV] or transmissions Aftermarket
remanufactured stator and rotor kits are becoming available for the
gen 2 & 3 Prius
Slide 83
83 Scan Tool Diagnosis Diagnostic trouble codes for most hybrid
and BEV drive systems using the Snap-On Modis or Verus DTCs will be
manufacturers specific codes normally in the P3xxx range The look
at serial data you will need to determine module label for the
Hybrid control module it may have a cryptic designation so look at
data from all modules until you see PIDs related to he hybrid
system Diagnostic trouble codes for most hybrid and BEV drive
systems using the Snap-On Modis or Verus DTCs will be manufacturers
specific codes normally in the P3xxx range The look at serial data
you will need to determine module label for the Hybrid control
module it may have a cryptic designation so look at data from all
modules until you see PIDs related to he hybrid system
Slide 84
84 Motor/Generator PID data Problems with the electric traction
motors will normally be visible in the serial data stream Each
stator coil has a temperature sensor Problems with the electric
traction motors will normally be visible in the serial data stream
Each stator coil has a temperature sensor Motor overheating could
be caused by a loss of coolant, water pump failure or a restricted
coolant hose
Slide 85
85 Motor / Generator PID data In addition to stator core
temperature PID data also includes the motor rpm and amount of
torque produced Negative torque values indicates the
motor/generator is operating in regenerative braking mode In
addition to stator core temperature PID data also includes the
motor rpm and amount of torque produced Negative torque values
indicates the motor/generator is operating in regenerative braking
mode Rr Motor refers to the rear traction motor on the Toyota
Highlander hybrid
Slide 86
86 Stator Test Connect three 12 volt test lights between each
of the stator leads Turn the rotor by hand Turn the crankshaft for
IMA and MG1 turn one drive wheel while holding the other stationary
to test MG2 All three light bulbs should flash with equal intensity
as the rotor turns Connect three 12 volt test lights between each
of the stator leads Turn the rotor by hand Turn the crankshaft for
IMA and MG1 turn one drive wheel while holding the other stationary
to test MG2 All three light bulbs should flash with equal intensity
as the rotor turns Test connections can be made at the transaxle or
inverter terminals after removing the service plug
Slide 87
87 Review The three basic components of a hybrid or BEV
traction motor are: Rotor Stator Resolver An IMA system has a
single electric motor located at the back of the engine block Two
motor hybrid systems have the electric motors located inside the
transmission The three basic components of a hybrid or BEV traction
motor are: Rotor Stator Resolver An IMA system has a single
electric motor located at the back of the engine block Two motor
hybrid systems have the electric motors located inside the
transmission
Slide 88
88 Review Most hybrid and BEV motors are liquid cooled and
share their cooling system with the inverter An electric water pump
circulates coolant through the traction motor and inverter BEVs
require a gear reduction unit to allow the electric motor to run at
peak efficiency while the wheels turn at a much lower speed Most
hybrid and BEV motors are liquid cooled and share their cooling
system with the inverter An electric water pump circulates coolant
through the traction motor and inverter BEVs require a gear
reduction unit to allow the electric motor to run at peak
efficiency while the wheels turn at a much lower speed