IEEE Power Electronics Magazine - September 2016 - 27

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Table 1. An overview of state-of-the-art conductive and contactless EV chargers.
source

Conductive

Contactless

1

P (kw)

V (dm3)

m (kg)

h (%)

t (kw/dm3)

c (kw/kg)

m-pec [www.mpec.at]

6.6

1.38

2.53

96.0

4.8

2.6

Whitaker2 et al. [3]

6.1

1.22

1.6

95.0

5.0

3.8

J. Everts [46]

3.7

1.85

2.68

95.6

2.0

1.38

Gautam et al. [47]

3.3

5.46

6.2

93.6

0.60

0.53

GM Chevrolet Volt [12]

3.3

6.71

10.1

89.6

0.49

0.33

Nissan Leaf 2013 [48]

3.3

10.9

16.3

85

0.3

0.2

Toyota Prius 2010 [3]

2.9

6.4

6.6

n/a

0.45

0.44

Primove 2003, 4 [25]

200

198

340

90.0

1.0

0.59

Bosshard5 et al. [37], [38]

50

18.5

25

95.8

2.7

2.0

Goeldi5 et al. [23]

22

22.4

n/a

97.0

0.98

n/a

Chinthavali et al. [12]

6.6

7.2

12.3

85.0

0.92

0.54

Brusa ICS1153 [21]

3.7

2.3

4.0

90.0

1.60

0.93

WiTricity WiT33003 [10]

3.3

1.8

4.0

89.0

1.83

0.83

Diekhans5, 6 et al. [24]

3.0

8.5

3.2

95.8

0.35

0.93

The State of the Art for Conductive
and Contactless EV Chargers
The presented analysis indicates that the required component volume, weight, and material costs for the IPT onboard components are higher than for a conventional
solution. This is confirmed by the data of existing onboard conductive EV chargers collected in Table 1. The
listed numbers for the conductive chargers include the
complete power-conversion chain from the mains to the
EV high-voltage battery. For the contactless chargers, only
the receiver coil is included for the volumetric and gravimetric power density. Data for industry prototype IPT
chargers [10], [21], [25] are compared in Figure 5. For completeness, the results for the 50-kW/85-kHz IPT system in
[37] are also included. It must be pointed out that the
listed commercial systems include structural elements for
mounting the coil on the vehicle and comply with automotive standards. For the work in [37], further modifications
are required to fulfill all automotive requirements. As a
comparison, the best-in-class 6.1-kW conductive EV charger described in [3] is also shown.

5

Efficiency
Volumetric Power Density
Gravimetric Power Density

6
5

4

4

3

3

2

2

1

1

0

0

Gravimetric Power
Density (kW/kg)

6
Volumetric Power
Density (kW/dm3)

100
98
96
94
92
90
88
86

C
6. ond
1 uc
kW ti
v
[3 e
]
3.
7
of kW
[2 IP
3. 1] T
3
of kW
30 [10 IPT
0 ]
of kW
[2 IP
5 T
50 ]
of kW
[3 IP
7] T

IPT power electronics is closer to that of a conductive onboard charger, given the similarity of the power-conversion
chains; see Figure 3(a) and [3].
For passenger EVs, a contactless system could be considered as an optional premium feature in addition to a
conventional conductive charger. In this case, integration
of the two on-board power converters reduces the required
constructive volume and the total cost for the charging
equipment. However, the major volume, weight, and cost
increase due to the receiver coil remains, despite the combination of the power electronics.

Mains-to-Battery Efficiency (%)

Remarks: For all contactless chargers, only the dimensions and weight of the receiver coil are included. 1Designed with Si CoolMOS devices. 2Designed with SiC
MOSFET devices. 3Data obtained from manufacturer upon request. 4The receiver is lowered to the street during charging. 5DC-to-dc efficiency. 6No coil housing
included.

FIG 5 A comparison of the main performance factors for a
conductive on-board EV charger, for industrially available IPT
chargers, and for the system presented in this work. The
power density for the IPT systems includes only the receiver
coil, whereas for [3] the complete system is included.

The listed data highlight that the efficiency of the
contactless EV chargers is reduced by approximately 5%
compared to the latest conductive EV chargers. This is
mainly due to the limited construction volume for the
receiver coil on the vehicle. Small receiver coils lead to
a low magnetic coupling even if, as in [21], a significantly
larger transmitter coil is used. As a result, a comparably
low transmission efficiency must be accepted for a contactless EV charger.
The outstanding performance of the conductive charger in [3] is achieved by the optimum utilization of silicon
carbide (SiC) power-semiconductor technology and a high
switching frequency for the miniaturization of the passive
September 2016

z	IEEE PowEr ElEctronIcs MagazInE

27
http://www.mpec.at
Table of Contents for the Digital Edition of IEEE Power Electronics Magazine - September 2016
