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Presenter: Dr John Reeve, Ricardo
WS2 partners: JLR, MIRA, Ricardo, TMETC, WMG, Zytek
(lead)
LCVTP WS2: Electric Traction Motors, and guidance to their practical application
WS2 Electric Traction Motors
Presentation topics
• The different Traction Motor topologies, and their
relative merits
• The different Hybrid-Vehicle architectures, and
their bearing on the choice of Traction Motor
• The Pitfalls of comparing Traction Motor
datasheets
• Deriving the requirements for a Traction Motor –
the LCVTP WS2 Motor Selection Tool
WS2 Electric Traction Motors
Traction Motor topologies
The three main Traction-Motor topologies
• Permanent Magnet
• AC Induction
• Switched Reluctance
Comparison of EM
topologies
WS2 Electric Traction Motors
Traction Motor topologies
Permanent Magnet
> Internal v. External rotor,
> Radial v Axial Flux.
> Highest specific torque and power
> Cost, RE materials
> Careful system design required for safety and smooth torque
delivery
> Adopted by Toyota and Honda
WS2 Electric Traction Motors
Traction Motor topologies
AC Induction
> Slightly lower efficiency, specific torque & power than PM,
= Usually larger and heavier per unit torque than PM
> Simpler design, cheaper materials = Generally lower cost
than PM
> Fewer safety considerations than PM
> Inherently smooth torque delivery
WS2 Electric Traction Motors
Traction Motor topologies
Switched Reluctance
> Similar efficiency, specific torque and power, to ACI
> Lower cost
> Careful design required to minimise operational noise
> Inherently robust with smooth torque delivery
WS2 Electric Traction Motors
HEV Architectures
HEV architectures, and their impact on EM choice
• Series, i.e. RE-EV
> Effectively an EV with a gen-set, so EM has to be capable of delivering
the full tractive torque and power
> Design considerations:
• System limitation likely to be thermal (EM, Inv, or battery)
• May benefit from 2 or 3-speed gearbox to reduce peak torque
demands on EM.
• Duration of high-power phases usually dictated by battery
• Duration and power of “constant” phases dictated by APU output
WS2 Electric Traction Motors
HEV Architectures
• Parallel (mild)
> Generally low torque & power and short duration of operation
> Key design considerations:
• Vibration (if affixed to engine), and physical sizing (to fit in
driveline)
• Parallel (full)
> Broader scope for EM positioning & mounting options
> Generally medium-high power and short-medium duration
> Key design considerations:
• Physical sizing for location
• Quantification of duty-cycle critical
WS2 Electric Traction Motors
HEV Architectures
• Battery EV (not a hybrid, but included for comparison)
> EM has to be capable of delivering full tractive torque
> Key design considerations:
• System limitation likely to be electrical power and/or energy
from battery
• Duration of high-power (peak) and “constant” phases
dictated by battery
• Low energy dissipation so may be air-cooled.
WS2 Electric Traction Motors
Pitfalls of comparing EM datasheets
When comparing torque & power
• Over what duration is “peak” and
“constant” being quoted?
• With what coolant conditions
(flow-rate, input temp, etc)?
• At what supply voltage, and rpm?
• As a complete system?
Some of these can be normalised
When comparing efficiencies
• Measured across a complete
system? !!! Important !!!
• If one figure is quoted, at what
speed/torque?
• And how does efficiency look
over rest of speed/torque map?
… and many more …
WS2 Electric Traction Motors
LCVTP Motor Selection Tool
Vehicle-level req’s:
• Category
• Vehicle spec
• Performance
• Additional req’s
• Sensitivities
• …
Motors’
Database
HL
MST
EM
Comp
Tool
List of matching or
“close-fit” solutions
LL
MST Drive Motor
Datasheet
- Sizing
Drivetrain-level req’s:
• LL Sensitivities
• Vbatt
• Main areas of operation
• …
WS2 Electric Traction Motors
Want to learn more? 13th July WS1-4, Digital Lab LCVTP WS1-4: High-Voltage System
Integration For more details,
see info on WMG website at http://tinyurl.com/6cbx4cd
or email: [email protected]