IEEE Electrification Magazine - June 2020 - 57

E (V/m)
3.00e+004
2.80e+004
2.60e+004
2.30e+004
2.00e+004
1.70e+004
1.40e+004
1.10e+004
8.00e+003
4.00e+003
2.00e+003

The Electric Field in Other Areas
Is Weak for Safe Operation
Vehicle Chassis
Receiver Plate

The Electric Field Only Concentrates
Between the Transmitter and Receiver
for Power Transfer

Electric Field

Long-Transmitter Track

Ground

Figure 9. A simulated electric field distribution in a dynamic CPT system, demonstrating its safe operation.

With a good insulation layer on
the plate surface, the corrosion
and aging of the plate can also
be limited.
xx
High efficiency and safety performance: In a dynamic CPT system, long-transmitting coils are
eliminated. To achieve high
power, the voltage is increased
and the current is reduced to
limit the conduction loss and
improve efficiency. Moreover,
because the electric field does
not generate any eddy-current
loss in metals, there is no concern for overheating.

Electric Field Emission
in a Dynamic CPT System

E (V/m)
3.00e+004
2.80e+004
2.60e+004
2.30e+004
2.00e+004
1.70e+004
1.40e+004
1.10e+004
8.00e+003
4.00e+003
2.00e+003

Vehicle Chassis

Metal Foreign Object
5-mm Thickness

Electric Field Is Not Significantly Affected
Ground

Long-Transmitter Track
Coupling Capacitance Variation Is Within 2%
(a)

E (V/m)
3.00e+004
2.80e+004
2.60e+004
2.30e+004
2.00e+004
1.70e+004
1.40e+004
1.10e+004
8.00e+003
4.00e+003
2.00e+003

Vehicle Chassis

Water Foreign Object
10-mm Thickness

Electric Field Is Not Significantly Affected

Applying a voltage excitation up to a
Ground
Long-Transmitter Track
few kilovolts on the capacitive couCoupling Capacitance Variation Is Within 5%
pler, a finite element method (FEM)
analysis provides the simulated elec(b)
tric field distribution depicted in Figure 9. A long metal track is used at Figure 10. The impact of conductive and dielectric foreign objects on electric fields in a dynamic
the primary side as the transmitter, CPT system. (a) A metal foreign object and (b) a water foreign object.
and a relatively small plate is used at
the secondary side as the receiver.
The ground plate and vehicle chassis are both included in
It is also common to have foreign objects existing
the simulation model to emulate the practical scenario. The
between the transmitter and receiver that could affect the
simulation model demonstrates that most of electric fields
power-transfer process. In different weather conditions,
concentrate between the transmitter and receiver, and the
such as wind, rain, and snow, there could be leaves, water,
electric-field strength in other areas along the transmitter
and ice on the roadway surface. These foreign objects can
track is relatively weak, which is good for safety.
be divided into two categories: metal and dielectric mateBecause the voltage on the vehicle chassis is limited to
rials. The FEM analysis is used to study the impact, and
a low value (<8.35 V), it acts as the shielding to the electric
simulation results are presented in Figure 10.
field emission. Figure 9 also shows that the field strength
For the conductive material, a piece of aluminum is anaabove the chassis is significantly reduced. In a practical
lyzed, and the electric field can pass through it. For the
vehicle, this means that the electric field inside the vehicle
dielectric material, water is adopted to represent the severe
is reduced, and the dynamic CPT system would be safe for
weather condition. When the water thickness is 10 mm,
the driver and passengers in the vehicle.
the simulation indicates that the power-transfer process is

IEEE Elec trific ation Magazine / J UNE 2 0 2 0

IEEE Electrification Magazine - June 2020

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