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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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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.
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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.
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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
10th International CTI Symposium, December 2011, Berlin
- Alexander.Fraser, Protean Electric Ltd.-
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