2. UWAFT Vehicle Powertrain
2.4 L LE9
E85
GKN9.59:1
Battery
Charger
Fuel
Tank
TM4 105 kW
Motor (Front)
A123 18.9 kWh
ESS
TM4 105 kW
Motor (Rear)
GKN7.47:1
TM4 105 kW
Generator
2:1BeltDrive
Electric Hybrid
Mechanical
Connection
Electrical
Connection
Single-Speed
Gear Reduction
Fuel
Connection
Legend
Component Specification
Engine: GM
2.4L LE9 Flex
Fuel
Peak
Efficiency
37%
Peak Power
131 kW @
5800 rpm
Peak Torque
230 Nm @
5000 rpm
ESS: A123
Systems Inc.
7 Module,
15s3p
Voltage 340 V
Energy 18.9 KWh
Peak Power 177 kW
Motor/
Generator:
TM4 MOTIVE
Peak/Cont.
Power
105 – 54 kW
Peak/ Cont.
Torque
180 – 70 Nm
Voltage
Range
320 – 450 V
Final Drives:
GKN Driveline
Front Ratio 7.47:1
Rear Ratio 9.59:1
Charger:
Brusa NL513
Peak Power 3.3 kW
Typical
Efficiency
93%
3. UWAFT VTS
Metric Design Target Requirement Actual
0-60mph (s) 9.5 11.5 6.8
50-70mph (s) 8.0 10 3.1
Top Speed (km/h) NA 120 151
60-0mph (m) 43.7 54.8 50
Vehicle Mass (kg) <2250 2250 2078
Vehicle Range (km) 322 322 400
EV Range (km) NA NA 42
Fuel Consumption (L/100km) 7.12 NA 4.34
WTW GTG Emissions (g GHG/km) 204 NA 169.3
Criteria Emissions T2 B5 T2 B5 T2 B5
4. General Fuse/Wire Selection
Fuse Selection Considerations:
• Nominal Operating Current
• Ambient Temperature
• Overload Conditions and Opening
Times
• Available Short Circuit Current
• Melting Integral
• Pulse and Inrush Characteristics
• Characteristics of Protected Equipment
• Physical Size
• Standard Requirements
Wire Selection Considerations:
• Ensure wires are compatible with SAE
J1127 and J1128 standard
• Peak Current Draw
• Wire Length
• Ambient Temperature
Wire Margins:
In General: Fuse is selected based on component characteristics
Wire is selected based on fuse characteristics
• For LV systems:
• For HV system cables selected
based on manufacturer
recommendations
5. Fuse De-Rating Example (Generator)
Fuse De-Rating Calculations
• Typical under hood temperature can reach 100OC
• Inside distribution box can reach 60OC
• for motor is 169A
Derating Factor Symbol Value
Max Permissible Current 𝐼 𝑏 180
Rated Current for Given Fuse 𝐼 𝑛 225
Ambient Temperature 𝑘 𝑇 0.8
Thermal Correction Factor 𝑘 𝑒 ~1
Cooling Air Correction Factor 𝑘 𝑣 1
Frequency Correction Factor 𝑘 𝑓 ~1
Correction for High Altitude 𝑘 𝑎 1
6. I2T Analysis Front Cooling Loop
• Includes pump and fan
• Fuse Rating = 20 A
• Lightning pulse characteristic
• Melting I2T = 520 A2S
• Pulse I2T = 227.40768
• Based on these calculations fuse was replaced
with 25 A fuse to limit nuisance fuse blows
8. Load Accommodation and Efficiency
Load Type Peak (UWAFT added) Load (A)
Nominal LV Load 52
Nominal LV Load with PHCC 152
Peak LV Load 113
Peak LV Load with PHCC 233
• GM APM connects 18.9 kWh HV battery to
480 Wh LV battery
• Additional loads are only activated when
required
• Pre-heated catalytic converter runs
less than 5 minutes
9. LV Parasitic Current
• Stock GM system has low parasitic draw, but must crank engine
• UWAFT has higher current draw, but no LV engine crank
• Why so high? Still running rapid prototyping tools
• For production remove controllers and development tools
System Stock UWAFT
Parasitic Current Draw (mA) 50 200
2 week Energy Drain (Ah) 16.8 67.2
12V Battery Capacity (Ah) 40 40
Vehicle No-Start Battery
Voltage (V)
10.5 9.5
Time to No Start (weeks) 4.75 1.2
10. HV Bus Voltage/Current Ripple
• Portion of drive cycle, stop and go traffic with CAN data
• Max speed = 60 km/h
• Max battery current = 115 A
• Max battery power = 38 kW
11. HV Bus Voltage/Current Ripple: 40s window
Measured
Parameter
Sampling
Rate
Peak-to-
peak
ripple
Voltage 100 kHz 1
Current 10 kHz 8
Battery Current Draw
Battery Voltage
• Voltage measurements
taken with ETAS HV
sensors connected to HV
Test port in rear
distribution box
• Current measurements
taken with hall effect
sensor connected to ETAS
LV sensors
12. HV Bus Voltage/Current Ripple: 400 ms window
• 200 Hz low pass filter
shows ripple low
frequency ripple of
~60 Hz on DC bus
• This ripple can be
attributed to long
and short term
transients from
battery
Battery Voltage
Battery Current
13. HV Bus Voltage/Current Ripple: 4ms window
• 1 kHz low pass filter shows 1.5 kHz ripple, likely a result of electric
motor frequency
• Unfiltered component shows pulses at 38 kHz which agrees with 2
inverters switching between 16 and 20 kHz each
Battery Voltage
14. HV Bus Voltage/Current Ripple
Summary
No apparent resonance issues
• TM4 input filters with X & Y capacitors limit resonance &
EMI/EMC issues
No resonance found in simulations
• Year 2 simulations show gain = 1.3 around 4-5 kHz
Based on these findings, UWAFT decided no design changes
were necessary
15. HV Bus Charge and Discharge Times
HV Bus Charge
HV Bus Discharge
• No engine start: motors are
readily available, key-on to
start time < 2 seconds
• At key off contactors opens
and TM4 inverters discharge
HV bus
• Bus capacitance = 1.875 mF
16. HV Safety and Serviceability
E-Stops LED Indicators
HV Warning Labels
Safe Vehicle Servicing
19. Challenge: Relay Control/Wiring
Front Relay Board Rear Relay Board
Generator Rear Traction Motor
Front Traction Motor BMS
Front Cooling Loop Rear Cooling Loop
Clutch DCDC Fan
HVAC Park Lock
HVIL1 HVIL Power
HVIL2 HVIL3
• Each relay requires a digital output pin
• To reduce wiring and free up pins on controller, CAN controlled
relay boards were implemented
• Based on Freescale S08D microcontroller
UWAFT Added Relay Components
20. Knowledge Transfer
Access to Tools
Partnership with Altium. Provides on-demand licenses for UWAFT team
members
Central Repository
New students can access all EcoCAR and EcoCAR2 documents
Mentorship Program
Pairs new students with senior members
Safety Training
All students get basic high-voltage training before working on the car
