Possibilities in Possibilities in Inductive Energy Transfer Inductive Energy Transfer Power Electronics Research Department of Electrical & Computer Engineering The University of Auckland Grant Covic, John Boys
Possibilities inPossibilities inInductive Energy TransferInductive Energy Transfer
Power Electronics ResearchDepartment of Electrical & Computer
EngineeringThe University of Auckland
Grant Covic, John Boys
Overview:Overview:
MotivationIPT ConceptsState of the ArtIPT ResearchChallenges
Motivation:Motivation:
Wireless Power
Motivation:Motivation:
Added Value:Wireless Data
IPT ConceptsIPT Concepts
IPT Systems:IPT Systems:Supply Current sourced
• Independent secondaries• Efficiency high under load (0 at no load)
Secondary can move
3∅Input
Power Supply
track conductor inductance = L1
I1
Switched-Mode
Controller
L2
DCpower
TunedPickup
PickupInductance
IPT Concepts:IPT Concepts:
Closely coupled– Transformer– Induction Motork typically > 0.98
21LLMk =
Loosely coupledIndividual k very low < 0.05
Primary recessed in floor: flat pick-ups
Rail mounted: E-core
Tuning:Tuning:
Primary: Reduce Supply VA Rating– Long Track: Series– Concentrated Coil: Parallel
Secondary: Improve Power Transfer– Current Source: Parallel– Voltage Source: Series
Voc
Isc
none
Series (QIsc)
Parallel (QVoc)QIVP scocout =
3∅Input
Power Supply
track conductor inductance = L1
I1
Switched-Mode
Controller
L2
DCpower
TunedPickup
PickupInductance
Parts of an IPT System:Parts of an IPT System:
UOA: Materials Handling using E pick-up
Non-permeable TrackGuide
(Aluminium or Plastic)
Plastic Supports
Ferrite
TrackConductors
Pick-up Coil
The Quest for More Power:The Quest for More Power:
Increase the track frequencyIncrease the track currentIncrease M or reduce L2
Increase Q
QLMIQIVP scoc
2
22
1ω==
Electronic Decoupling Controller:Electronic Decoupling Controller:
R
S
MI
DCL
DCC
)1(22 2
1 DVLMIP o −⋅⋅=
π
L21
State of the ArtState of the ArtSystemsSystems
The Present State of the Art:The Present State of the Art:
Automotive applicationsClean Factory AutomationPeople movingBattery ChargingTraffic ControlPower transfer Applications
Automotive: Monorails & AGV’sAutomotive: Monorails & AGV’s
Daifuku & Wampfler
•100m Sections•10 trolleys @ 750W
• AGV 3kW • Batteries• V 30mm• L +/- 30mm
Automotive: SkilletAutomotive: Skillet
Daifuku
Automotive: Hoists & AGVsAutomotive: Hoists & AGVs
Daifuku
Clean Factory Automation:Clean Factory Automation:
Daifuku: Clean Room Systems
Automotive:Automotive:
Wampfler: Rail Applications
Japan Public Works Research InstituteTest Track for new road pavements
• 1 vehicle• 90 kW power• 165 m track length• Vehicle weight 22 tonne• Speed 30 km/h
10kW Pickup
Sorting:Sorting:
Wampfler: Rail Applications
•4 x 1.5 kW Power (75 or
48Vdc)•Track Length
~ 210 - 280 m
Paris (Carrefour), Turin, London
People Moving:People Moving:
Wampfler: Rail Applications
• 3 kW power transfer• for cabin lights, doors, ventilation window heating, communications• Track length ~ 65 m
EXPO 2000, Hanover, Germany Hermes Tower Outdoor Elevator
Automotive:Automotive:
Wampfler: Rail Applications
• 15 vehicles• 6.6 kW each• Track length ~75 m
BMW, GermanyFloor Conveying System
Automotive:Automotive:
Wampfler: Rail Applications
AUDI, Germany: Floor Conveying System Engine Assembly Line
• 58 vehicles• 1.5 kW per vehicle for drive, lift and swivel motors• Track length ~ 2 x 180m
Automotive:Automotive:
Wampfler: Rail Applications
BMW, Germany: Floor Conveying System Engine Assembly Line
• 35 vehicles each requiring 1.5 kW • Track length ~ 150 m
People Moving:People Moving:
Wampfler: Charging- discontinuous power transfer
People Moving:People Moving:
Wampfler: Charging flat pick-ups
• 5 buses with trailer• 3 x 10 batteries of 12 V • Charging: 7min /15-20 min• Charging power: 20 kW
Whakarewarewa People Mover, Rotorua, New Zealand
People Moving:People Moving:Power supply– Modified AC inverter
Charging bays– Rapid charging– Computer controlled
WhakarewarewaRotorua
Wampfler: 20kW charging stations
People Moving:People Moving:
Wampfler: Charging flat pick-ups
Genoa, Porto Antico
• 3 buses each with 56 x 6V Batteries• Charging 60kW for 10 minutes/hour
State of the Art:State of the Art: Weil-am-Rhein
Primary Coils
Pickups
Energy Supply (Current) Cooling System (Water)
Wampfler: 60kw Charging station
M
State of the Art:State of the Art: Genoa, Porto Antico
Supporting Frame for Pickup
Lowering Mechanism for Pickup
30 mm (max)
M
Wampfler: Charging
Traffic Control: Traffic Control:
Hardings: Road studs with flat pick-ups
Roadway lighting• 2km/ 2kW • 1 Stud/10m @ 2W• 38.4kHz at 16A
Wellington TunnelIllinois, USA
Pedestrian Crossings• 200W• 20 Studs• Slow Comms (1kb/s) (FM Modulation)
IPT Research IPT Research ProgramsPrograms
IPT Research: Wish ListIPT Research: Wish List
Low System CostPrimary Supply– Minimum VA rating– Stable power transfer – Drive long track lengths– Load shedding for peak power
Movable Pickups– Low Size & Weight– Excellent Magnetic Coupling– Self tuning
Communications– Low Cost/High Bandwidth
IPT Research: Major ProgramsIPT Research: Major Programs
Electromagnetic designRoadway systems Power regulatorsCommunicationsPower suppliesPower schedulingHarmonics and standardsTransient behaviour
Electromagnetic Electromagnetic DesignDesign
Pick-up Design: Pick-up Design: ExperimentalExperimental
Litz Cable
52mm
doff-centre
la
lg
0.00
5.00
10.00
15.00
20.00
25.00
30.00
0 20 40 60 80 100 120 140 160
Distance off centre (mm)
MAO
P at
h=5
2mm
(VA)
MAOP la=86
MAOP la=120
MAOP la=155
MAOP la=190
MAOP la=230
• Power 1/80th Scale• 72% of final frequency• Estimation required for final system
QLMIP
2
22
1ω=
Pick-up Design: Pick-up Design: FEM AnalysisFEM Analysis21mm49.5mm 49.5mm
3mm
18mm
FEM Analysis:FEM Analysis: Gaps & Multiple Pick-upsGaps & Multiple Pick-ups
Air gap size (mm)
Impacts of Air Gaps
Leakage flux
Track
Track
Constructive Mutual Coupling
Destructive Mutual Coupling
FEM Analysis: FEM Analysis: Ferrite PositioningFerrite Positioning
Roadway SystemsRoadway Systems
Roadway Systems: Roadway Systems: Single PhaseSingle Phase
• Traditional Single phase Flat Pick-ups
•Flat-E •Simple Flatscocu IVS =
0
2
4
6
8
10
-150 -100 -50 0 50 100 150Distance from Track Centre (mm)
Unc
ompe
nsat
ed P
ower
[Su]
0
2
4
6
8
10
-150 -100 -50 0 50 100 150Distance fromTrack Centre (mm)
Unc
ompe
nsat
ed P
ower
[Su]
Roadway Systems: Roadway Systems: MultiphaseMultiphase
• 3Φ LCL Resonant Converter & Open-Delta Track
A+C-
B+
A-
C+
B-
A+ C- B+ A- C+ B-
Ferrite
3-phaseinverter LCL NetworkDC Input
LCL Network
LCL Network A+C-B+A-C+B-
Roadway Systems: Roadway Systems: ComparisonsComparisons
Three Phase vs. Single Phase
•Simple Flat 40A/phase at 38.4kHz•3 Φ wire spacing 40mm•1 Φ wire spacing 100mmscocu IVS =
0
2
4
6
8
10
12
-150 -100 -50 0 50 100 150Distance from Track Centre
Unc
ompe
nsat
ed P
ower
[Su]
Three Phase Open DeltaSingle Phase
Power RegulatorsPower Regulators
Power Regulators:Power Regulators:
R
L2
C2 S
D
C3
+
M
1I
Voc
L3
V0
Resonant poles
Control pole
Output pole
"""""" OUTCONTROLRESONANT fff >>>>
3∅Input
Power Supply track conductor inductance = L1
I1
Switched-Mode
Controller
L2
DCpower
TunedPickup
PickupInductance
Active Tuning:Active Tuning:Variable VAR Device
Pick-up Controllers– Maintaining resonance with high Q– Re-tuning for magnetically enhanced tracks
Power Supply & Track Tuning
QLMIP
2
22
1ω=
IPT CommunicationsIPT Communications
An Ideal IPT Comms System:An Ideal IPT Comms System:
Low-cost Non-contacting Maintenance free High data rate > 8.7 MB/s Bolt-on system Long rangeIsolation between IPT systems
300 Ohm ribbon & Antenna Mounting:300 Ohm ribbon & Antenna Mounting:
300MHz: Pin 0dBm
y = -0.222x - 24.692
-35
-30
-25
-20
-15
-10
-5
00 2 4 6 8 10 12 14
Distance along track (m)
Sign
al re
ceiv
ed (d
Bm
)
Conclusions and ChallengesConclusions and Challenges
Specific Systems engineered for – Monorail, CFA and Road studs
Floor Mounted AGV’s & Battery Charging – Crude
Transient Analysis– Electrical & Magnetic needs to be done
Magnetic materials – unacceptably brittle (Ferrite)– Expensive (Amorphous) and not isotropic
Power Electronics:– Capacitors, Switches are limiting– New technology required for larger power sizes (trucks & trains)
Integration of power, data and controlImproved performanceLower Cost
Questions ?