Power Electronics Research at the University of Nottingham Professor Pat Wheeler Email: [email protected]Power Electronics, Machines and Control (PEMC) Research Group UNIVERSITY OF NOTTINGHAM, UK The University of Nottingham Professor Pat Wheeler Email: [email protected]
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Power Electronics Research at the University of Nottingham
• Machine-drive topologies working at high frequency – High poles/high speed
• Manufacturing – automation, additive– New structures
• Advanced thermal management
Electrical and mechanical integration
High frequency
machines
20kW/L,
SiC converter
Thermal material
integration
Performance Limits
Hybrid Propulsion Systems
Modern Trends in Aircraft Electric Power Systems and in Onboard Electric Power Generation
Engine Propulsion
Fuel Energy Storage
EMEMEMEM EMEM EMEMEMEM EMEMEMEM
TurbineTurbine
Electric Propulsion Electric Propulsion
Electric Starter/Generators
Power Electronic Converters
Battery Electrical Energy Storage
Fuel Cell Electrical Energy Storage
Fast-Responce Electrical Energy
Storage (SuperCap)
Electric Loads (WIPS, EPS, EMA, etc)
EPS control and energy
management
TurbineTurbine
“Single-bus” approach is employed!
Potential TeDP EPS architecture:- gas turbines drive generators, and optionally may act as direct propulsion devices- distributed electrical machines drive propulsion devices- energy storage devices can be used to buffer energy- overall EPS control/energy management
Modern Trends in Aircraft Electric Power Systems and in Onboard Electric Power Generation
High-power machine design for hybrid platforms
- MW-class equipment
- Efficiency/losses become a critical design factor
- High speed gen-sets- Close Integration with GT- Very high power density requirement- Thermally/Mechanically challenged
- Low-speed propulsion motors- Very high torque density- Electromagnetically/Thermally
challenged
Generator
Gas Turbine
Propulsors
EM
EM
Converter
Case 1: Starter/Generator System
Aircraft Starter/Generator
Overall drive system – machine choice
Selected Solution• Slot-Pole Combination – 36-6
• 6 pole to limit switching
frequency loses
• distributed winding
• low rotor losses
• Solid rotor with a CF sleeve retention
• Stiff rotor
• Quasi Hallbach array
• Large airgap = low rotor loses & adoption
of a stator sleeve
8k rpm
19k rpm
32k rpm
motoring
generating
Aircraft Starter/Generator
Power Converter Selection
• Up to 1.6kHz electrical frequency at maximum speed
• Maximum current: 260Arms peak, 270V DC
• Low harmonic content to minimize rotor losses
• Air cooled – significant impact on heat sink weight
Design ConceptSwashplate attachment and EMA arrangement
Jam-tolerant design required due to the jamming risk in ball screw
Redundant EMAs
Requirement to replicate hydraulic system space envelope
Arrangement of 2 EMAs side by side
Hydraulic swashplate actuator arrangement 6 EMAs, each pair
connected to output rods
• Models needed for all the parts of the system
– Reliability– Functional– scalable
Optimisation System Optimisation - models and tools
Parameter Lower Boundary Upper Boundary Unit
Airgap Diameter d 24 35 mm
Split Ratio SR = d/D 0.4 0.6 -
Tooth-width factor 0.5 0.7 -
Fin extension 1 8 mm
Fin thickness 1 3 mm
Fin pitch/thickness 2 8 -
Optimisation with Particle Swarm Optimisation algorithm:
• Simulates behaviour of bird flocks to find optimum of non-linear
functions
• Number of particles with random initial position and velocity
• At each iteration step velocity is
updated with attraction to personal
best particle position
• Efficient optimisation method for
electromechanical problems
• Optimisation with 6 parameters
applied for this design:
dD
L
Particle Projection Evolution of Drive Weight
Optimisation Detailed Design Optimisation
Hardware ConstructionActuator, Motor and Power Converter
Stator
Phase A1
Phase C1
Phase B1
Phase B2
Phase C2
Phase A2
Rotor
Completed Motor
PowerConverter
Short Circuit Motor Current and Drag Torque
Actuatorwith two motors, each motor has two independent stators
Electromagnetic Aircraft Launch Systems for Civil Aircraft
• Electromagnetic Launch (EML) system used
to replace steam catapults on the deck of
aircraft carrier.
• Steam catapult have a number of disadvantages
• Operate without feedback control
• Bulky and heavy
• Highly maintained
• Inefficient (4-6%)
• Adoption of EML in military application was slow
• Recently technical advances have been good for the technology:
• Pulsed power
• Power conditioning
• Energy storage
devices
• Advanced
controls
Electromagnetic Launch Systems
Requirements Data
Aircraft mass 73500 kg
Take-off speed 85.73 m/s
Acceleration 0.60 g
Peak Thrust 502.9 kN
Runway length 624 m
Take-off time 14.57 s
Minimum cycle time 90 s
Electromagnetic Launch Benefits 1
1) Runway length reduction
An acceleration of 0.6G was chosen - compliance with the maximum axial acceleration that a human body can comfortably withstand.
The runway length computed assuming a uniformly accelerated motion to the rotation speed VR plus a safety distance equal to the 25% of the acceleration path.
𝑽𝑹 = Τ𝟏. 𝟎𝟓 𝑽𝟐 𝟏. 𝟏𝟏
Electromagnetic Launch Benefits 2
2) Fuel consumption and exhaust emission reduction
Assume all the energy required to accelerate the aircraft can be saved.
Consider a CFM56-5B4 on the Airbus A320-200, the total fuel burnt during take-off can be computed as
𝐹𝑢𝑒𝑙 𝑏𝑢𝑟𝑛𝑡 = 2 𝑒𝑛𝑔𝑖𝑛𝑒𝑠 ∙ 1.166𝑘𝑔
𝑠∙ 42 𝑠 = 𝟗𝟕. 𝟗𝟒 𝑘𝑔
Considering an airport like Heathrow with 650 flights per day yields
𝐹𝑢𝑒𝑙 𝐵𝑢𝑟𝑛𝑡 𝐷𝑎𝑖𝑙𝑦 = 97.94𝑘𝑔
𝑡𝑎𝑘𝑒 𝑜𝑓𝑓∙ 650
𝑡𝑎𝑘𝑒 𝑜𝑓𝑓
𝑑𝑎𝑦= 𝟔𝟑𝟔𝟔𝟏
𝑘𝑔
𝑑𝑎𝑦
The NOx emission is equivalent of that of 80180 diesel car son daily base
HC CO NOx
Emission indices (g/kg) 0.1 0.5 28.7
Daily emission reduction (kg) 6.37 31.83 1827.07
Electromagnetic Launch Benefits 3
3) Noise Emission reduction
Aircraft engines usually take 4-5 seconds to accelerate from idle to maximum powercondition. The overall noise emission reduction at ground level is expected to be
𝑁𝑜𝑖𝑠𝑒 𝑟𝑒𝑑𝑢𝑐𝑡𝑖𝑜𝑛 =42 − 5 𝑠
42 𝑠∙ 100 = 𝟖𝟖. 𝟏 %
4) Engine size reduction
In the hypothesis of an EML system installation on a large number of airports, the enginerated thrust could be updated to that required during climbing or during emergencyprocedure (approximately 85% of the thrust required at take-off).
This would lead to reduced aircraft drag and weight
EML System Requirements
Requirements F-35C A320-200 Comments
Take-off speed [m/s] 78 70Data taken from references
Aircraft mass [kg] 37000 73500
Acceleration [G] 3.3 0.6F-35C launcher length is set by the dimensions of the aircraft
carrier and the launch acceleration is function of it. The
launcher acceleration for civil application is a requirement and
its length is later determined.Runway length [m] 94 535
Peak thrust [MN] 1.198 0.548 (0.455)Peak Thrust and Launch Energy of military launcher are
calculated considering only aircraft inertia, while those for the
civil application consider the contributions of aerodynamic
drag and ground friction. Inertia contribution is reported
between brackets.Launch energy [MJ] 113 210 (182)
Comparison of launcher requirements for F-35C and for an A320-200 .
Motor Technologies
Superconducting Permanent Magnet Induction
Complex design, costly and significant additional equipment
Linear Permanent Magnet has higher efficiency and
simpler and cheaper. The mover is more robust and lighter.
Expensive, efficiency savingsnot significant in this application
Lacks robustness, may incur magnets demagnetization
Lower efficiency, but this is a system with a low duty cycle
Superconducting linear motor
design
Permanent magnet linear motor performance
Permanent magnet and
induction motors
IntroductionEML?
• Electric Ground Aircraft Launch Systems
• Reduce engine requirements
• Extend maximum flight distances
• Save aviation fuel
• Increase payload
• A different way of thinking…
Landing
• More Electric Aircraft: – Still challenges to address– Flying aircraft a good way to test technology
• All Electric Aircraft – Technology requirements are demanding and
not possible today– Hybrid will be followed by true electric if we can
address all issues
• Electromagnetically assisted aircraft take-off– An out-of-the-box approach– Advantages are many– Infrastructure requirements are daunting!