in-wheel electric · pdf file · 2017-04-06in-wheel electric motors ... • it...

10th International CTI Symposium, December 2011, Berlin

- Alexander.Fraser, Protean Electric Ltd.-

In-Wheel Electric Motors The Packaging and Integration Challenges

Alexander Fraser, Protean Electric Ltd

10th International CTI Syposium, December 2011, Berlin



Summary

•Introduction to Protean Electric & the Protean Drive

•Requirements & Protean Design Philosophy

•Target Markets and Performance Requirements

•Safety Requirements

•Cable Routing

•The Diameter Advantage

•The Direct Drive Advantage

•The Protean Drive Package

•The Brabus EV based on the Mercedes-Benz E-Class



Company Introduction

Protean Electric:

• A clean technology company

• 90 employees, mainly engineers

Protean Holdings Corp

(US)

Protean

Electric GmbH

(Germany)

Protean

Electric

Inc (US)

Protean

Electric Ltd

(UK)

Company structure:

• Venture Capital backed (Oak investments) with main technical

operations in the UK

• Corporate operations in the UK, US and Germany

Company focus:

• Developing a dedicated automotive in-wheel motor system

• Developing & protecting IP in the core technology

• Enabling customers traditional supply chain through licensing

• Focus on reducing risk and maximising shareholder value



Protean Drive Overview

Brushless

Permanent magnet

Outer rotor

Direct drive

Water cooled

High pole count

Large diameter (toroidal form)

4 Sub-motors per motor

Integrated inverters



Summary





•Cable Routing







Battery electric & series hybrid vehicles

• Motors are the only source of tractive effort

• 2WD and 4WD Passenger vehicles <3500kg GVW

Parallel hybrid vehicles

• In-wheel motors work in parallel with ICE powertrain

• Two in-wheel motors to give significant fuel savings

• Passenger cars and light commercial <3500kg GVW

Retro-fit ability paramount!

• Motors must integrate with minimal platform tear-up

• Releases platform space with minimal risk

• Must occupy common spaces, and not prevent driveshafts

for parallel hybrids

Target Markets – the Starting Point



Torque Requirements for Gradeability

• 1000Nm peak torque & 700Nm continuous torque gives

excellent 2WD & 4WD coverage

• It is not necessary to match 1st gear ICE wheel torque to

provide credible vehicle performance



Safety Requirements

Protean’s safety concept

• Through application of ISO 26262 & ECE R13H

• No single fault shall cause the driver to lose control

• No unintended braking (or acceleration!)

• Individually driven wheels give a unique problem –

unsafe vehicle yaw moment if wheel fault torques not

limited.

• Protean’s research gives typical torque disturbance

limits of ~250-300Nm (C-segment vehicle.)

• Clearly require more performance than the torque

limit, so the failure modes and mitigation strategies

must be understood.



1x 1000Nm Actuator

• Potential large

fault torques for

all failure modes

• Vehicle-level

mitigation

required for

many failures

• Phase fusing

required for

phase shorts

4x 250Nm actuators

• Most failures only

affect ¼ motor

giving lower fault

torques

• ¾ of motor can

compensate

• Much less vehicle-

level mitigation

• No phase fusing

required

Motor Sub-division



On-Vehicle Inverters

• ++ Easy electronics

environment

• - High AC resistance

and inductance

• -- Practically impossible

routing proposition

Integrated Inverters

• ++ Manageable routing

• + Lower AC losses

• + More space on body

• - Harsh environment

• - Tight space

Cable Routing for

a Subdivided

Motor



Direct Drive Advantages Transient Performance

• Best control fidelity, excellent slip control opportunities.

Reliability & Safety

• Direct drive gives minimum relative moving parts - simplicity

• Gearboxes are single points of failure – yaw moments again!

• Require high reliability, or clutches, adding cost and/or size.

Wheel bearing deflection

• A brushless motor can be deflection tolerant relatively simply

• A gearbox must transmit forces across deflecting surfaces,

adding cost and size

Retro-fit and package size

• Brake torque through a gearbox impractical – will require

rotor duplication in many motor package shapes

• Although gearing will allow the motor to be located off-axis,

this can result in heavily restricted motor diameter in order

to allow retro-fit capability.



Diameter Advantages Direct drive:

• Torque is key to vehicle performance

Increasing diameter gives:

More cross-sectional area for electronics

Better Nm/kg

Better Nm/litre

Must be able to package wheelbearing or

suspension through the centre of the motor



The Packaging Choices Following all requirements derived by Protean, 3 locations

to package motor remain

A. Small diameter, long length

B. Large diameter, around both brake & suspension

C. Occupy brake space, design new brake



The Protean Packaging Choice

Package volume set from “collage” of many suspensions

Results in a toroidal motor form

Can package wheelbearings in the motor centre



The Protean Packaging Choice

Fits within 18” or larger wheel – C-Segment and above

Outer rotor – max air-gap diameter, cooling, brake mounting

Configurable around many bearing types

High pole count – package size, low cogging, low noise



Summary





•Cable Routing







The Brabus EV based on the MB E-Class

Retro-fit battery electric vehicle based on the W212 E-Class

3200Nm/320kW peak torque/power at the wheels

56kWh Lithium ion battery (up to 350km range)

3-String pack

Water/glycol cooling

On board fast chargers

100% passenger and cargo space retained



The Brabus EV based on the MB E-Class

Centralised electric drivetrain would not have been

possible to package without serious compromises to the

on-body passenger and cargo space

http://www.cardotcom.com/photos/news01/2011-brabus-full-electric/brabus-electric-10.jpg



The Brabus EV Motor/Brake Package

Prototype brakes designed and manufactured by Alcon

Inside-out discs with sliding hydraulic calipers

Floating mounting between motor rotor and brake disc

Allows unrestrained thermal expansion of disc

Thermally isolates heat-sensitive motor rotor from hot

brake

http://www.alcon.co.uk/index.php



The Brabus EV Thermal Performance

Excellent thermal isolation of

motor rotor from brake disc

Disc tested to >600 degrees C

during cracking tests

Rotor did not exceed 80 degrees

C during the same tests



Thank you for your attention Any questions?

in-wheel electric · pdf file · 2017-04-06in-wheel electric motors ... • it...

Documents