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ISCAD - 48V Traction Drive
-
Advantages and Challenges
Dieter Gerling
Universität der Bundeswehr München
ISCAD - 48V Traction Drive
development of costs for battery packs
2
●
estimated for Chevy Bolt
estimated for Tesla Model S
● ●
estimated for Tesla Model 3 (Gigafactory)
ISCAD - 48V Traction Drive
standard system up to now for high power traction
3
= 3 ̴ M
ca. 375V ca. 150V
ISCAD - 48V Traction Drive
possible system architecture with low voltage DC circuit
4
electrical machine
power electronics DC electrical system
M
48V
⁞ ⁞
battery
ISCAD - 48V Traction Drive
stator „winding“ evolution
5 Quelle: derkonstrukteur.de
distributed winding
concentrated winding
stator cage winding
ISCAD - 48V Traction Drive
building the entire electrical drive
no more coils, massive stator cage instead
perfect utilization of available space: • perfect slot filling factor • no end-windings
great thermal behavior • low thermal resistance bar – iron • water cooled end-ring possible
minimum production cost • aluminum instead of copper • simple production, e.g. die-casting, low invest
extremely smooth rotating field • individual bar currents • very high efficiency
6
ISCAD - 48V Traction Drive
ISCAD (Intelligent Stator Cage Drive) e.g. as induction motor with changing number of poles during operation
7
ISCAD - 48V Traction Drive
changing the number of pole pairs during operation (exemplary calculation)
8
p=3
p=2
p=1
ISCAD - 48V Traction Drive
best-in-class overload capability
9
This overload area can be used by ISCAD (machine and power electronics) because the voltage limit is not reached
ISCAD - 48V Traction Drive
ISCAD: power electronics generations
10
Gen 1
Gen 2
Gen 3
ISCAD - 48V Traction Drive
power electronics: losses at partial load
advantages of MOSFETs in relevant driving cycles
lower forward voltage at partial load (𝑅𝐷𝐷,(𝑜𝑜)𝐼1 instead 𝑉𝐹)
further optimization potential for MOSFET inverter
11
𝑃𝐿 ↓ ↓ 𝐿𝐿𝐿𝐿𝐿𝐿
ISCAD - 48V Traction Drive
DC wiring
larger cross-sections for higher currents short distances for light-weight, aluminum instead of copper
300 hp example (5 kA)
• distance: 1 meter • material cost: < 5 € • conductor mass: < 5 kg
large contact surface
flexible coax conductors using metal braid
• compact design • perfect shielding of electromagnetic fields
12
ISCAD - 48V Traction Drive
top class efficiency
13
Evaluation of Machine and Inverter Losses ISCAD Improves Efficiency by 20% to 25%
𝑃𝐿 ↓
Time (s)
0 200 400 600 800 1000 1200V
eloc
ity (k
m/h
)0
30
60
90
120
Time (s)
0 200 400 600 800 1000 1200 1400 1600 1800
Velo
city
(km
/h)
0
35
70
105
140
NEDC
WLTC
ISCAD - 48V Traction Drive
top class efficiency
14
numerous additional advantages
MOTOR
extremely cost-efficient
no copper, no magnets
extremely robust
ISCAD - 48V Traction Drive
15
BATTERY
drop out of single battery cells does not result in large capacity reduction
simplified BMS
simplified CID
increased available capacity and lifetime (against higher voltages)
POWER ELECTRONICS
drop out of single half-bridges does not result in large power reduction
power electronics and electrical machine are perfectly integrable
high switching frequency
improved EMI characteristics
common cooling with electrical motor
SYSTEM
electrically intrinsic safe system
effort for high-voltage training of employees (R&D, production, maintenance, etc.) is avoided
12V-supply is simple and very cost-efficient (low voltage DC/DC-converter)
scalability of the system is very simple (same power electronics modules for all different power levels)
best-in-class availability
very low system costs
ISCAD - 48V Traction Drive
Conventional BEVs ISCAD – 48V Drive
16
NO DANGER LOW
VOLTAGE
SUITABLE FOR ANYBODY
ISCAD - 48V Traction Drive
main challenges
contacts with low ohmic resistance
conductive high power charging
main advantages
electrically intrinsic safe system
extremely cost-efficient
no material supply issues (e.g. copper, rare-earth magnets)
best-in-class system availability
perfect scalability
extremely high partial-load efficiency -> reduction of battery capacity (same range)
unsurpassed acceleration power
no high-voltage training of employees 17