Possibilities in Inductive Energy Transfer

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:


•4 x 1.5 kW Power (75 or

48Vdc)•Track Length

~ 210 - 280 m

Paris (Carrefour), Turin, London

People Moving:People Moving:


• 3 kW power transfer• for cabin lights, doors, ventilation window heating, communications• Track length ~ 65 m

EXPO 2000, Hanover, Germany Hermes Tower Outdoor Elevator



• 15 vehicles• 6.6 kW each• Track length ~75 m

BMW, GermanyFloor Conveying System



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



BMW, Germany: Floor Conveying System Engine Assembly Line

• 35 vehicles each requiring 1.5 kW • Track length ~ 150 m


Wampfler: Charging- discontinuous power transfer


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


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 ?

Possibilities in Inductive Energy Transfer

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