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: lowcarbon@warwick.ac.uk