**4. WPT-systems for charging EVs**

**Figure 7** depicts the base components of a WPT system for EV charging. It consists of two prime sub-systems, one of which is existing underneath the road surface and the second is found into the vehicle underbody [14]. The first subsystem includes the source of energy, rectifier and high frequency inverter, primary compensation network and the primary/transmitter coil (Tx). The built subsystem in EVs, has the secondary/receiving coil (Rx) and secondary compensation network composes a resonance circuit that supplies into a high frequency rectifier, filter and the battery. The sub-systems are separated by an air gap. The distance between the two systems depends on the type of vehicle, ground clearance and road conditions such as pavement thickness. Usually the air gap is smaller than 0.4 m. Additionally, both sub-systems share information via a communication link.

The system given in **Figure 7** includes:


*Wireless Power Charging in Electrical Vehicles DOI: http://dx.doi.org/10.5772/intechopen.96115*

**Figure 7.** *(a) The base components of a WPT system for (b) EV charging system.*


**Table 2.** *SS, SP, PS, PP compensation topologies.*

Moreover, different types of coil design are used in WPT, such that Circular, Flux pipe/flat solenoid, Bipolar, Tripolar, Zigzag, DD and DDQ [20–26].

Efficiency of resonant WPT with SS and SP topology, and of an inductive WPT vs. QR for different values of QT is reported in **Figure 9a**, while the efficiency of

> *QT*,*<sup>R</sup>* <sup>¼</sup> *<sup>ω</sup>L*1,2 *R*1,2

*<sup>k</sup>* <sup>¼</sup> *<sup>M</sup>*ffiffiffiffiffiffiffiffiffiffi *L*1*L*<sup>2</sup>

*QT,R*: Transmitting and the receiving quality factor, respectively. *k*: Coupling coefficient. L1 and L2 are the s self-inductances of the transmitting and the receiving coils, M is their mutual inductance, and R1 and R2 are the coil resistances. To charge or transfer energy into the vehicle electric storage device, many electrical charging methods are established and standardized. This methods are

p (4)

(3)

resonant WPTS with PS and PP topology is given in **Figure 9b**.

*Efficiency of resonant WPTSs with SS, SP, PS and PP topology [12].*

*Wireless Power Charging in Electrical Vehicles DOI: http://dx.doi.org/10.5772/intechopen.96115*

given if **Figure 10**.

**37**

**Figure 9.**

**Figure 10.**

*Classification of charging method for EVs.*

#### **Figure 8.**

*Power transfer efficiency characteristics under varying mutual inductance [26].*

• The core components of the WPT system are two coupled coils that allow power transfer via magnetic field [19]. Electric current flows through the primary coil and produces a time-varying magnetic field around it. In the nearness of the primary coil, the secondary coil intercepts the magnetic field, which induces a voltage. The value of induced voltage depends on the air gap length between these coils, the number of turns and the value of dφ/dt; φ is the magnetic flux.

*Wireless Power Charging in Electrical Vehicles DOI: http://dx.doi.org/10.5772/intechopen.96115*

**Figure 9.**

*Efficiency of resonant WPTSs with SS, SP, PS and PP topology [12].*

**Figure 10.** *Classification of charging method for EVs.*

Moreover, different types of coil design are used in WPT, such that Circular, Flux pipe/flat solenoid, Bipolar, Tripolar, Zigzag, DD and DDQ [20–26].

Efficiency of resonant WPT with SS and SP topology, and of an inductive WPT vs. QR for different values of QT is reported in **Figure 9a**, while the efficiency of resonant WPTS with PS and PP topology is given in **Figure 9b**.

$$Q\_{T,R} = \frac{aL\_{1,2}}{R\_{1,2}}\tag{3}$$

$$k = \frac{M}{\sqrt{L\_1 L\_2}}\tag{4}$$

*QT,R*: Transmitting and the receiving quality factor, respectively. *k*: Coupling coefficient. L1 and L2 are the s self-inductances of the transmitting and the receiving coils, M is their mutual inductance, and R1 and R2 are the coil resistances.

To charge or transfer energy into the vehicle electric storage device, many electrical charging methods are established and standardized. This methods are given if **Figure 10**.

Furthermore, there are many other many electrical charging methods uses different converters among different renewable sources [27, 28].
