IEEE Electrification Magazine - September 2013 - 62

stationary wireless charging has its merits. First,
-stationary wireless charging systems can be completely
autonomous, requiring minimal action from the driver.
This feature can maximize opportunity charging since
the user often forgets or chooses not to charge when the
vehicle is parked for short periods of time. In addition to
convenience, wireless charging improves the safety of
the charging process. By removing cords and cables, the
trip hazard associated with wired chargers is nonexistent. The chargers are vandal proof and have no risk of
electric sparks. Low maintenance requirements increase
the reliability of the charger. On the other hand, the electromagnetic emissions of the charger must be considered
in the system design. The magnetic field can present a hazard when an object is placed in the magnetic link. Therefore, the system must have a robust foreign-object iden-

Table 1. Driving Range Without IPT (in Miles).

Insight (8 kWh)
Explorer (15 kWh)

UDDS

HWFET

HW-MTN

38.17
36.09

37.14
33.00

22.99
18.83

Table 2. IPT Coverage Required for 300-mi

Range (30 kW Delivered to Vehicle).
Insight

Impala

Explorer

UDDS
Coverage (%)

0.46

0.91

tification system that turns the system off when there is an
obstruction in the magnetic link.
In addition to one-for-one replacements of conductive
chargers, wireless charging technology is ideally suited for
opportunity charging scenarios, where the vehicle is parked
at a predetermined location for a short period of time. The
concept is particularly well suited for mass transit applications, where the wireless charger can be installed at bus
stops, allowing the vehicle to charge while the passengers
are embarking and disembarking from the bus. This concept is being used successfully for two lanes of public transportation in Turin, Italy, and many other cities.
The design of a stationary charger consists of a primary
pad buried in the ground and a pickup pad mounted on the
underside of the vehicle. The primary pad is typically sealed
in rubber or covered with plastic to prevent the coil from
flooding and/or other hazardous situations. It frequently
contains ferromagnetic materials to shape the magnetic
field, and metal rings or plates that reduce the leakage
of the magnetic field. An implementation of the system
is shown in Figure 4, with a representation of the system in
Figure 5. A similar pad structure to the one shown in
Figure 4 is attached on the underside of the vehicle. The primary pad might sometimes be elevated by several centimeters to reduce the vertical distance between the coils. An
automatic guidance system can be installed in the vehicle
to help the driver align the vehicle directly above the primary pad. The charging station and the vehicle exchange data
by using the inductive link or other short-range communication methods. This feature allows the charging station to
adjust the charging procedure according to the condition of
the battery or the driver's preferences.

Dynamic Charging of EVs

HWFET

First, we look at the infrastructure requirements for
dynamic wireless charging. These results were first reportHW-MTN
ed in a previous publication [1]. We considered three vehicle
types (compact car: Honda Insight; large car: Chevrolet
Coverage (%)
17.2
35.4
64.3
Impala; and SUV: Ford Explorer) fitted with small battery
packs (8, 11, and 15 kWh, respectively)
operating on three types of driving
cycles [low-demanding urban driving
Vehicle Components
Station Components
cycle (UDDS), highway driving cycle
A) Vehicle Adapter
D) Indicator Panel
B) Vehicle Electronics Module
E) Power Control Module Connected to 240-V Power
(HWFET), and highway driving in a
C) Battery Charger Connection
F) Parking Pad
mountainous region (HW-MTN)]. Our
simulations show that the vehicles
have a very short driving range, never
D
exceeding 50 mi (see Table 1). We then
determined the section of the roadway
C
that needs to be IPT-enabled to extend
E
the vehicle range to 300 mi. The
B
results, when the optimization algoA
rithm tries to minimize the length of
F
the roadway that needs to be powered,
are summarized in Table 2. Figure 6
Figure 5. An illustration showing the setup of stationary wireless chargers. (Image courtesy
of Evatran Inc.)
shows a graphical representation of
Coverage (%)

27.3

I E E E E l e c t r i f i c atio n Magaz ine / september 2013

43.8

Table of Contents for the Digital Edition of IEEE Electrification Magazine - September 2013