IEEE TEC DL 2017 - Inductive Power Transfer

Inductive Power Transfer
TEC IEEE Distinguished Lecturer Series 2016
Professor Grant Covic
Friday, 11 August 2017
Professor’s G. A. Covic and J.T. Boys
Inductive Power Research Group
Dept. of Electrical and Computer Engineering

Overview
• Future Vision
• Wireless Power Transfer: A Brief History
• Fundamentals of resonant WPT/IPT
• Early Developments at U.o.A.
• Industrial Track Systems
• Charging Applications
• Future Road Systems

IPT street Conductive charge street
Safe and Durable
Aesthetically pleasing
Easy to use
Vision of Future City
Autonomous, Connected, Electric and Wireless

WPT/IPT HISTORY
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Copyright: Uniservices Ltd. 2017
Email: ga.covic@auckland.ac.nz

• 1894: Hutin & Le Blanc (proposed power to rail conductors)
• 1890s-1920s: Tesla (CPT and WPT tuned resonant coils)
• 1960s-70s Biomedical Applications with resonant coupling
• 1974 -75: Otto (NZ), Bolger (US) propose roadway power
• 1980s: Bio-implants, Guided Roadway projects (Santa Barbara project),
aircraft entertainment
– uncontrolled or detuning controllers
• 1990s: Industrial applications in materials handling, Robotics and
People mover systems (including buses)
– fully independent decoupling controllers
• 2000s: Planar electronics, Cellular phone applications, heart pumps,
Commercial bus systems
• 2010s: Stationary EV charging trials, Light rail and buses
Powering on the move
Brief Historical Overview IPT

“Transformer System for Electric Railways”
• Proposed inductive moving railway vehicles on rail conductors
• 1-2kHz track frequency
• Capacitive compensation of pick-up
• Multiple pick-ups used for various power ratings
• Could only transmit signals
1894 - Hutin and LeBlanc US patent 527857
Brief Historical Overview IPT

Wireless Power Transfer History
• Nikola Tesla
A "world system" for "the transmission of electrical energy
without wires"
Teslas Capacitive Power Transfer (CPT) demo in 1891 [1]

A Sceptical Background:
• “Inductive Power Transfer cannot be done”:
– Signals: Yes
– Tooth-brushes: Yes
– Real Power: No!
• “Even if power could be transferred control could be
impossible”
• Background & timing
– power electronics, resonant circuits, electromagnetics
– Invented new controllers allowing multiple independent
vehicles on one supply

US Patent 3914562 “Supplying Power to Vehicles”
• Pickup mechanically raised and lowered
• First system technically feasible
1975 - Bolger
Wireless Power Transfer History

Santa Barbra Project
• Roadway Powered Electric Bus (1980~1996)
– Low efficiency, gaps 5-7cm
– Secondary 1mx4.3m, 7500kg, variable tuning
– High construction cost : 0.74 ~ 1.22 M$/km

WPT FUNDAMENTALS
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Wireless Power Transfer
• Reliable & convenient
• Tolerant of water, chemicals, and dirt.
• Regarded as impossible for 200 years
V
I
H
Ampère’s Law
Faraday’s Law
su oc sc
P V I
 

• The two observables in the coupled coil cannot be
observed at the same time
– The Open Circuit voltage:
– The Short Circuit Current:
• Un-tuned VA Coupled into the secondary coil L2:
1
MI
j
VOC 

2
1 L
M
I
ISC 
Fundamentals of WPT
2
2
1
2
su oc sc
M
P V I I
L

 
V
I
H
Ampère’s Law
Faraday’s Law
su oc sc
P V I
 
M is the mutual inductance between the track and the
secondary coil

jωMI1
RL
V2
C
L2
I2
jωMI1
RL
V2
L2
I2
C
 To increase the power
 Tune at the track frequency
Parallel Tuned
Acts like a current source
Series Tuned
Acts like a voltage source

 
 C
L2
0 1
Why Secondary Tuning?

 Tuning boosts power by circuit Q2:
 But secondary VA also increases:
 And circuit bandwidth decreases:
 Reflected impedance onto the primary is:
 Load dependant
 Tuning dependant
2
o su
P P Q

0 2
BW Q


2
2 2
su
VA PQ P Q
 
Tuning Summary

The Tuned Output Power
Dependent on:
– Frequency
– Track current
– Magnetic Coupling
– Primary & Secondary Operating under Resonance
2
2 2
2 1 2 1 1 2
2
oc sc
M
P V I Q I Q V I k Q
L

       

EARLY DEVELOPMENTS AT UOA
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What to do with a HF Load resonant Inverter?
Motivation & Vision
Controlling power to many secondary's independently
Managing bifurcation in variable frequency systems

Early Load Resonant Supply
• Current sourced push-pull
• Supply frequency varies with changes in:
– Tuning capacitor C1
– Track inductance L1

Motivation
Wires are messy & insecure

3
Input
Primary
I
Switched
Mode
Controller
DC
Secondary
Compensation
Secondary
Power
Power Supply
+ Output
Compensation
Litz Wire
Power Electronic Switches and Capacitors
Modern Microprocessor Controllers
Modern Ferrites
Reliant on Latest Technologies

Our Vision for WPT
Controllable, safe and efficient
– Field shaping methods operable over a wide frequency
range and applications
– Systems with low leakage
– Highly efficient
• High quality factor components
• Operating quality factors that ensure they are less sensitive
to the environment
– Controlled operation under highly resonant conditions

Moving platforms – a first step
• History of trailing wires, brushed or mechanical chain
and pulley
• Connections were a major problem
• Environments were very dirty or ultra clean.
Wireless offered:
• Galvanic isolation
• Unaffected by dirt, water, chemicals
• Particularly clean – producing no residues
• No trailing wires
• No sliding brushes
• Maintenance free

1990: A First System at the UoA.
2mm Operating air-gap
 Alignment non critical
 No power regulation
 Maximum 1 trolley/track
 Large pick-up coil
 Resonance to overcome low k
 Low efficiency
But it worked!!!
100 pair telephone cables
Brushless DC Driving Motor

Daifuku Requirements
 Power rating/secondary > 200 Watts each, all independent
 System Efficiency > 75%
 Delivery < 4 Months
 Special terms Payment on completion
Assistance with components

We had:
 15 month old toy system
 No appreciation of the inherent difficulties
 No idea how to achieve independent secondary controllers
 4 months to produce a working 3-trolley system!

Pick-up & Controller on Monorail
 Required New Secondary Magnetic Design
 New Approach to Control - Decoupling

Pick-up development:
Wood and ferrite rods Cut Toroid's
ETD-49 development

Final magnetic development
• Custom Ferrite system assembled

Frequency Stability Problem
• At heavy load there are two stable operating points.
• To avoid bifurcation total secondary VA < the track VA.
Light Load Heavy Load

The first decoupling load controller
• Enabled
– Each Load could be removed (decoupled)
– independent load control using switch duty cycle (0D1)
– Controlled resonance and secondary VA

Other Decoupling Controllers
• Series tuned
• Unity Power Factor (LCL)

Prototype Comparison
Original System Daifuku Prototype
Power rating 1W 400 W
Efficiency <10% 85%
# of Carriers 1 3
Load 75 kg 250 kg
Speed 0.1 m/s 1 m/s
Track current 80A 80A
Track length 3 m 25 m
Air-gap 2 mm 4 mm

Aluminum Monorail
Pick-up Coil
Ferrite E
Core
Track Wires
 Allowed movement
 Tolerant of misalignment.
 Unaffected by the environment
Prototype Operation

Fixed Frequency Supplies
• Single Phase LCL Topologies
– Low energy bus
– UPF input stage
VLF
Inverter
Bridge
Isolation
Transformer
Primary Track Inductor
(L1)
ZL
C1
Effective Inductor with isolation
(Lp=L1)
load coupled to
track
Ø
N
E
Mains Line Filter
Fuse
220V,
50Hz,
2 KW
Input
Cdc C1
L1
Zload
A Ip
B
Lb
Cb
LP=L1
UPF

INDUSTRIAL TRACK SYSTEMS
Stationary and moving systems
Guided mechanically on monorails
Guided electronically above buried tracks (AGVs)
The quest for greater freedom
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Constant primary current, as multiple secondary's
Each individual secondary k very low < 0.05
Primary recessed in floor: flat pick-ups Rail mounted systems: E-core
New IPT Systems 1990’s
Loosely coupled & highly resonant:

Metrics for Multiple Secondary's
M
L1
L2
Load
Secondary
Compen-
sation
Secondary
Power
Control
VLF
Power
Supply
Utility
Supply
Primary
Compen-
sation
leakage
Elongated Track
leakage
2
1L
L
M
k 
 k is a system co-efficient
 Doesn’t fairly represent how good the magnetics are
 Kappa looks at the coupling without leakage

Problem: Flux Cancellation in E-Pick-up
ФB-A
Track
Conductor A
(excited)
Track
Conductor B
(not excited)
ФL2-A
ФlA
Track
Conductor A
(excited)
Track
Conductor B
(excited)
ФL2-A
ФlA
ФL2-B
ФlB
Improving the Magnetic Design
}
{
}
{
2
}
{ lA
c
A
B
c
A
L
A
c 





 

}
{
}
{
A
c
A
B
c
ICCF





Magnetic redesign: E to S Core
Solution: remove the flux cancellation path

Pickup design: S Core
no cancelation path but more difficult to use
S-pickup on ICPT track

S Core E Core
Voc (rms) 35.7 V 20.1 V
Isc (rms) 4.4 A 4.0 A
Su 158.5 VA 80.8 VA
FEM Analysis:
 Uncompensated power comparison
 Identical material usage
 Complex assembly

Factory Automation
Daifuku: Materials Handling

Electronic Factory Automation
Daifuku: Clean Room Systems

Conductix-Wampfler (IPT Technology)
Automotive Materials Handling

ACHIEVING GREATER FREEDOM
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AGV Systems
Multiphase Tracks
Multi-coil pickups
Combinations

AGV Systems Early 2000s
• Redesigns to enable freedom of movement
(Tolerance)
• Multiphase track options
• Multiphase Secondary options in a single
secondary

AGV’s and Robots
Precision alignment required for power transfer
0
1
2
3
4
5
6
-150 -100 -50 0 50 100 150
Distance fromTrack Centre (mm)
Uncompensated
Power
[Su]

MULTIPHASE TRACKS
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Multiphase tracks: 3
Vl - l C
L
L
Vl - l
C' L/2
L/2
2C
2C
1:2
a
b c
Vd
c
C1
C1
C1
C2
C2
C2
Track A+
Track A-
Track B+
Track B-
Track C+
Track C-
1:2
3 supply with 3 LCL track configuration
Creation of the LCL Circuit
Single phase track One phase of a three phase track
Vl - l C
L
L
C' L/2
1:2

The Three Phase Inverter
Track Compensation
Controller 3  Delta
Transformer
DC Blocking
Capacitors

Three Phase Control
3-phase
inverter
3-phase Isolating
Transformer & LCL
Network
Control
Circuit
Open-
Circuit
Protection
DC Input Track
3-phase
inverter LCL Network
DC Input
Control
Circuit
LCL Network
LCL Network
A+
C-
B+
A-
C+
B-

Causes of Inter-Track Coupling?
• Physical layout of the track loops
• M varies with the amount of overlap
• Can be calculated
-1
-0.5
0
0.5
1
1.5
2
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Overlap
Mutual
Inductnace
per
Unit
Length
(uH/m)

Effect of Track Coupling
• Unwanted voltages are induced in nearby conductors
because of currents in other phases
• Each phase acts as a pickup, powered by the other phases

Effect of Track Coupling
For LCL track topology with constant (regulated) I1
• The voltage induced in each track
– Varies based on M between tracks (given by V2 = jMI1)
– This drives a constant current back into the inverter
(Magnitude given by V/XL)
– Unwanted current is out of phase, and adds loss
• May charge the DC bus capacitance
I1
V2

Avoid the Inter-track Coupling
• Move the track loops to a point where M = 0
• Overlap = 0.29
• Good for supply
• Bad for power transfer
• Only suitable for 2-phase tracks
0
10
20
30
40
50
-200 -100 0 100 200
Offset from Track Center (mm)
Uncompensated
Power
(VA)
0.29
0.667
-1
-0.5
0
0.5
1
1.5
2
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Overlap
Mutual
Inductnace
per
Unit
Length
(uH/m)

Cancel The Mutual at Terminals
• Add a lumped element to the track
• Equal in magnitude but opposite phase
• Inter-coupling still exists, but zero at the inverter terminals
• Perfect power transfer
• Tricky to get exactly right
• Doesn’t scale well to higher powers

Balanced Overlaps
• Can balance each mutual with crossover points
• Increases track length
• Use a shared DC bus to prevent charging as some small
power transfer still occurs

Measured Track Waveforms
Three phase track currents
with some imbalance
Improved track currents
Using mutual cancelation

Three phase tracks
Multiphase tracks

Multiphase tracks
0
2
4
6
8
10
12
-150 -100 -50 0 50 100 150
Distance from Track Centre
Uncompensated
Power
[Su]
Three Phase Open Delta
Single Phase
• New 3-phase design provides:
– Excellent lateral tolerance
– Higher power

Multiphase Tracks with Ferrite
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
2850 3350 3850 4350
P
su
(kVA)
Offset along track (mm)
0mm 100mm 200mm 300mm 400mm
240A/phase, 20kHz, 20cm height

MULTI-COIL PICK-UPS
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Single Coil Arrangements
HORIZONTAL FLUX CAPTURE VERTICAL FLUX
VERTICAL FLUX CAPTURE
Uncompensated Power for Horizontal Coil
0
20
40
60
80
100
120
140
-150 -120 -90 -60 -30 0 30 60 90 120 150
Pickup Displacement (mm)
Power
(W)
Uncompensated Power for Vertical Coil
0
20
40
60
80
100
120
140
-150 -130 -110 -90 -70 -50 -30 -10 10 30 50 70 90 110 130 150
Power
(W)

Combination adds significant lateral tolerance
Maximises usage of the flux already captured
0
100
200
300
400
500
600
700
800
900
-150 -120 -90 -60 -30 0 30 60 90 120 150
Power
(W)
Vertical Coil
Horizontal
Coil
Vertical +
Horizontal
Specified Power
Specified Range
Independent Multi-coil Pick-ups
PICKUP
CONTROLLER

Ferrite removed to accommodate the horizontal coil
Improved Multi-coil Pick-ups:
Change Magnetic Shape

Inproved Multi-coil Pick-ups
L2V C2V
L2H C2PH
LDC
S CDC
RL
C2SH

COMBINED SYSTEMS
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Two Phase Tracks with Multicoil
Power profiles using multicoil pickups
125A/phase, 20kHz
Single coil on 2 phase track
Multi-coil on 2 phase track

3-phase tracks vs. Meander
Identical number track wires and current
• 80mm (3 phase) vs. 100mm separation meander
• Both have 40A/phase
• Three phase more than 3-4 times better (at centre)
• Similar lateral tolerance

Multiphase Tracks & Multi-coil Pads
Single coil Multi-coil
• Combined multi-coil
– Flatter power profile
– 25-50% more power

CHARGING APPLICATIONS
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Example Developments
Design Metrics
Operating Methodologies
Effect of Coupling
Magnetic topologies
- Non polarised vs polarised
- Multi-coil Topologies

People Moving (Mid-late 1990s)
Whakarewarewa
Rotorua Charging Bay
IPT Technology (Conductix-Wampfler)
• 5 buses with trailer
• 3 x 10 batteries of 12 V
• Charging: 7min /15-20 min
• Charging power: 20 kW

People moving (early 2000s)
IPT Technology (Conductix-Wampfler)
Genoa, Porto Antico
• 3 buses each with 56 x 6V Batteries
• Charging 60kW for 10 minutes/hour

50W Robotic Charging
Gripper Arm
Camera
Laser
Sonar
Bumpers
ID
Marker
IPT
Power
Supply
IPT
Power
Pad
Pressure
Pad
Wireless Charging as required
ID marker identifies
charger position

200W Shopping Basket Chargers
Charging Mat in Walmart USA
IPT powered shopping baskets
Power pad sited under trolley
Charging Station

Wider Applications
• Telemetry (now Millar research)
– Heart pumps
– Biomedical sensors
• Power by Proxi
– Home applications
– Inductive Slip-rings
Battery
Converter
Primary Coil
Pick-up Coil
Power Buffer
LVAD

• Secondary: robust, thin and light
• Primary: Robust is critical
• Cost effective & efficient
• Excellent coupling with low leakage
– meets ICNIRP
• Scalable for cars, trucks or buses
– Ground clearance is vehicle dependent and varies with
suspension, loading …
– Horizontal tolerance aids unassisted parking
Design Metrics

Design Metrics
• Good pad quality factors
– 20kHz QL  300-400
– 85kHz QL  500-700
• Typical coupling factor: 0.1< k < 0.25
• Magnetic Efficiencies (primary – secondary: 96-98%)

2
1 1 2
out
P V I k Q

Operating Methodologies
 Power output:
V1 regulated for safety
I1 increases power (but also losses)
 Operating Q of the primary (ground) pad
 Operating Q of the secondary (vehicle pad)
 Losses in any pad as function of Pad quality
 Control Options
 Primary side control only: Only Q1 varied
 Secondary side control only: Only Q2 varied
 Primary & secondary side control: Both Q1 and Q2varied.
Achieves lowest loss

Effect of Coupling
• Power impacted by k2
– If k2 = 0.1 the VA in the primary or secondary (or a
combination) must be 10x greater than Po
– If k2 = 0.01 the VA in the primary or secondary (or a
combination) must be 100x greater than Po
2
1 1 2
out
P V I k Q


Effect of Coupling
Magnetic loss concepts (assume pads with similar QL ~500)
Pout
3.3kW 0.316 0.10 33kVA 10 1 ~3.3kVA
3.3kW 0.316 0.10 10KVA 3.16 3.16 ~10kVA
3.3kW 0.316 0.10 3.3kVA 1 10 ~33kVA
3.3kW 0.10 0.01 330KVA 100 1 ~3.3KVA
3.3kW 0.10 0.01 100KVA 31.6 3.16 ~10kVA
3.3kW 0.10 0.01 33KVA 10 10 ~33kVA
~ Loss in
primary pad
~ Loss in
Secondary pad
Total Pad Losses
500 0.10 10 2% 1 0.2% 2.2%
500 0.10 3.16 0.63% 3.16 0.80% 1.4%
500 0.10 1 0.2% 10 2.5% 2.5%
500 0.01 100 20% 1 0.2% 20%
500 0.01 31.6 6.3% 3.16 0.63% 6.9%
500 0.01 10 2% 10 2 % 4%
( )
loss operating L pad
P Q Q


NON-POLARISED COUPLERS
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Plastic Cover
Coil
(Litz Wire)
Coil Former
Aluminium
Ring
Aluminium
Backing Plate
Ferrites
Circular Pad

Circular Coupler Shielding
Installation - EV chassis modification

Charger: 2kW single phase supply
Pick-up: 2-5kW Power Pad
220mm airgap
Vehicle
controller
2kW IPT Charger at EVS24
A Demonstration System

0 5 mT
160mm
Tx. Pad
Ferrite
Rx. Pad
Coil
Al
Coil
Circular Coupler Limitation
• Power null in all directions (around 80% pad radius)
• Suitable for stationary applications, challenging for movement
0
100
200
300
400
500
600
700
800
0 50 100 150 200 250
P
su
(VA)
HorizontalOffset(mm)
Simulated Measured

POLARISED COUPLERS
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Intra-pad flux
Pole face
Ferrite
Flux Pipe
Leakage
Flux pipe:
• encourages pole separation
• flux path has greater height
Issues:
• Fields on both sides & ends
• Hard to control leakage
Polarized Designs: Solenoid
Front
Back
Flux
out of
end

0
100
200
300
400
500
600
700
-400 -200 0 200 400
Flux
density
(uT)
Position along contour above pad (mm)
0
100
200
300
400
500
600
700
-400 -200 0 200 400
Flux
density
(uT)
Position along contour above pad (mm)
Position along contour (mm) Position along contour (mm)
200mm
z
x
Pd Pl
Flux path height, f(Pd/4) Flux path height, f(Pl/2)
(c) (d)
(b)
(a)
Circular vs. Solenoid Coupler
0 A/m2
106
Solenoid aluminium shield creates large losses
I1 = 23A/coil
• QL without shielding is 260 (20kHz)
• QL with shielding is 86 (20kHz)
Circular QL (~ 300 at 20kHz)

Ferrite strips:
• Reduce material and inductance
Coil winding:
• Creates a flux pipe (minimised winding length)
• Single sided flux paths with height ~ pole seperation /2
QL ~400 (20kHz)
Polarized DD & Single Sided Fields
Winding
direction
Flux path
height hz
0 mT
3.5
Φ1a
Φlt
Φlb
ΦM
Coils
Ferrite
Shield
Flux linkage
around return
portions
x
z
Fl

Polarised DD
0
500
1000
1500
2000
2500
0 50 100 150 200 250 300
P
su
(VA)
Offset in either x or y axes(mm)
DD (x) DD (y)
z
y x
Performance with lateral offset

Performance Comparisons
• Similar Areas and Inductances of Pads
• Similar Driving VA and Frequency
• Similar Secondary VA
• 7kW output at 125mm

Non-polarized vs. Polarized
Polarized on Polarized
Circular on Circular
7kW zone
7kW zone
Charging Area
Circular < 2x Polarised
Transfer height d/2
Transfer height d/4
Winding
direction
Flux path
height hz

MULTICOIL COUPLERS
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Multi-coil DDQ Secondary
A second coil added to DD
• Spatial quadrature coil
• Improves lateral tolerance
DD Coils Q Coil
Ferrite

Multi-coil on Various Primaries
Charging area 3 x greater
Polarised Primary
Non-Polarized Primary

Bipolar Option
• Independent coils (bipolar uses 25-30% less copper)
• Power transfer similar (Bipolar < 10% different to DDQ)
• All high QL Coils
• Can shut either coil down when not needed to maximise 
Quadrature
DD
BIPOLAR COILS
L2Q
L2DD
CsQ (Opt)
C2Q
Cdc
S
Diode
Ldc
C2DD
R

Bipolar primary & secondary
• Coupling factors for mismatched primary and secondary pads
– Bipolar, circular and solenoid options of identical area

Tri-polar Pads
• Rotationally tolerant to all including polarised and circular
• Has capability to boost VA in added coil for high power
• Compatible will all other technologies
• Can be used to reduce flux leakage at offset by as much as
50% for identical power transfer

Affixed vehicle pad &
Transmitter pad
3.5kW & 7.5kW Chargers >90%
HaloIPT Evaluations
Rolls Royce Phantom 102Ex with HaloIPT wireless charger

FUTURE ROAD SYSTEMS
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MAINTAIN 25MPH
Green Light Timer: .08sec
Dynamic EV Charging
Stationary & Dynamic
Around town: little & often
Semi-Dynamic EV Charging
Static EV Charging
AVAILABLE PARKING
0.0 miles ahead.
WARNING SIGN
Construction zone in 2 mi.
!
Wireless
charging

Roadway Vision
Semi-dynamic options, Smart Cities (rail, bus…)
High Capacity Highways
 Sequentially Energised Pads
 Independently controlled, tracking at > 100km/h
 Automated vehicle recognition, billing …
Vision Challenges:
 Compatibility
 Robustness
 Longevity

Stationary & Dynamic
www.primove.bombardier.com
http://olev.kaist.ac.kr/en/index.php
Buses (KAIST)
 Extended to Light rail & Buses
 Buried cables replace catenaries
 Semi-dynamic powering
 Signal lights, Taxi ranks, Hill climbing
 Reduces battery size & EV cost
 Long Distance & Off route
 Dynamic Powering on High Capacity Highways
 Plugin Slow for off route charging
 Fast charging on longer distance routes

WAVE Confidential & Proprietary – Do Not Distribute
Current
Wave Wireless Power Transfer
www.waveipt.com

Light Rail: Continuous 270kW power, buried cables replaces catenaries
Bombardier Dynamic IPT
Bus: Dynamic trials lowered pads at controlled height, Stationary lowered for 100-200kW
www.primove.bombardier.com

Charging 20-100kW
17 cm gap
Inductive strips sized for Bus
Is
Pick-up
Power supply rail
moving direction (x)
lateral displacement
ferrite core
KAIST OLEV Dynamic IPT
http://olev.kaist.ac.kr/en/index.php

Power
Supply
cabinet
Vehicle lane
IPT Track
Power
Supply
cabinet
Vehicle lane
Power
Supply
cabinet
Power
Supply
cabinet
IPT Track
IPT Track
IPT Track
Pad
Pad
Pad
Pad Pad Pad
Pad Pad
Pad
Pad
Pad Pad
Pad Pad Pad
Pad
200m
100m
Roadway Vision
 Sequentially Energised Pads under the Vehicle
 Coupled power to each independently controlled pad
 No DC or mains under roadway

Laboratory Scale Dynamic Highway
Detection and synchronization for power
Reference [26]

Semi-Dynamic Taxi Rank System
60 kW
PFC
60 kW
3 phase parallel
21.25 kHz
power
supply
Intermediate
pickup 1
10 kW 85
kHz inverter
LCL or G1
10 kW
biploar
pickup
Grid
3 φ
400V
Intermediate
pickup n
...
Boost/
buck
converter
10 kW 85 kHz G1
inverter with
integrated
converter
Energy
storage
Aluminium litz
backbone
∞ pickup
Vehicle
magnetics
Electric
vehicle
10 kW 85
kHz inverter
LCL or G1
Road
magnetics

Conclusions
• IPT Development
– Imagined 1890s
– Rediscovered in 1970-80s
– Commercially practical mid-late 90s in niche markets
– Impacting our home market today
• Opportunities & Challenges
– Broad set of applications
– Reducing costs & meet expectations
– Developing standards & meeting emission restrictions
• A future without being tethered to wires
– Home applications (appliances and cars by 2020)
– Robotics, Space, Automated warehousing – next 10 years
– Roadway powered EVs (evaluations 2020, in place > 2030??)

IEEE TEC DL 2017 - Inductive Power Transfer

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