Electromagnetic Induction Wireless Power Transmission Efficiency

Research

NingNing Chen

College of Mechanical and Electrical and Information Engineering,

Jiangsu Vocational and Technical College of Finance and Economics, Huaian, China

Cnn_110@126.com

Keywords: Wireless Charging, Transmission Efficiency, Simulation.

Abstract: Using the theory of mutual inductance coupling theory and establish mathematical model for the coupling

coil wireless charging, is obtained by analyzing the key factors influencing the electromagnetic induction

wireless power transmission efficiency: two coil radius relative position and relative size, coil, coil number

of turns, working frequency and load, etc. Then by using Maxwell's software control variable method is

used to simulation analysis was carried out on the key factors. According to the simulation results, summed

up the method of improve the efficiency of the wireless charging equipment transmission.

1 INTRODUCTION

In recent years, along with the advance of science

and technology, the traditional way of charging

already can't satisfy people's needs, under the

background of the wireless charging technology.

The existing wireless charging technology there are

four main ways: electromagnetic induction method,

magnetic resonance (NMR) method, to electric field

coupling mode and radio reception mode.

Electromagnetic induction technology products on

the production cost is lower than other techniques.

Due to the wireless charging technology based on

electromagnetic induction transmission efficiency is

influenced by many factors, so the wireless charging

technology based on electromagnetic induction

study transmission efficiency is particularly

important.

Maxwell is a powerful, accurate and easy to use

2D / 3D electromagnetic field finite element analysis

software, Maxwell has a wizard style user interface,

high accuracy of the adaptive split technology and

powerful postprocessing features, 3D Maxwell for

high performance 3D electromagnetic design

software, Maxwell can analyze the eddy current,

displacement current, set skin effect and proximity

effect, the motor, bus, transformer, coil and other

components of the overall characteristics, power

loss, coil loss, a certain frequency of impedance,

torque, inductance, energy storage and other

parameters can be automatically calculated. At the

same time can be given the whole phase lines, B/H

distribution, energy density, temperature distribution

and other graphic results. The software allows

engineers to simulate complex electromagnetic

fields.

2 ELECTROMAGNETIC

INDUCTION PRINCIPLE OF

WIRELESS CHARGING

Electromagnetic induction wireless charging through

energy to realize the energy transfer coupling coil,

the basic principle is in the sender and the receiver

have a coil, send the coil connected high-frequency

alternating power supply cable, and generate

electromagnetic signal, the receiver coil receives the

change of the electromagnetic signal, namely the

induced electromotive force, through the rectifier

filter circuit as dc voltage regulator, supply wireless

charging equipment batteries, the charging process is

completed.

Wireless charging system equivalent diagram is

shown in figure 1 (Junyong et al., 2012). Assuming

that AC power supply voltage for Us, circuit

resonance frequency for ω; The transmitter coil

current i

, the impedance of the transmitter coil for

, transmitter coil equivalent resistance of R

, the

transmitter coil inductance for L

, transmitter coil on

the capacitor C

, accept coil current i

, accept the

500

504

Jiang T. and Cheng J.

Speech De-noising based on Wavelet Transform and Genetic Algorithm.

DOI: 10.5220/0006029505040509

In Proceedings of the Information Science and Management Engineering III (ISME 2015), pages 504-509

ISBN: 978-989-758-163-2

impedance of the coil as the z

, accept coil

equivalent resistance R

, accept coil inductance of

, accept the capacitance on the coil for C

, launch

mutual inductance between coils and receive coil for

M; The impedance of the load for R

Figure 1: Schematic diagram of electromagnetic induction

of WPT.

According to the circuit system diagram can get

circuit impedance equation:











22L22

1111

C1/jLjRRZ

C1/jLjRZ



(1)

By using kirchhoff's voltage law is available:







































MjZ

Z



(2)

By (1) (2) available for current equation:































Mj-

MZZ



(3)

Assumes that the transmitter coil and accept coil at

the same resonance frequency, so

ωL

=ωL

=1/ωC

So the impedance of the

circuit equation:











L22

RRZ

(4)

So the output power of the load of PL and power

supply output power for Ps equation:









MZZ

RiP







(5)



1SS

MZZ







(6)

Charging efficiency can be represented as (Ying et

al., 2003):









212

MZZZ









(7)





 



L21L2

MRRRRR







As you can see, the transmission efficiency and M,

ω, R

, R

, including mutual inductance L, M and

coil axial spacing coil radial dislocation S, receiving

coil diameter D, transmitter coil diameter D, closely

related to the coil number of turns N (Huiping and

Xueguan, 2007).

3 MAXWELL MODEL

ESTABLISHMENT

The simulation steps of the 3D Maxwell model

include: select the type of solver, establish the 3D

model, set up the material properties, set the

boundary conditions, set the excitation, the grid

partition, the finite element calculation and the result

processing.

Firstly analyzed the influence of the ferrite of

coil, ferrite in wireless charging coil design has two

main functions: 1) enhance the magnetic field

intensity, reduce the magnetic flux leakage, for flux

1 the low impedance path; Isolation of metal

material to the absorption of the magnetic field; 2)

increase the induction distance, improve the coil

inductance and quality factor (Na et al., 2012).

Different ferrite materials because of the different

permeability, frequency characteristics, has a great

influence on the coil inductor, ferrite loss. Using

Maxwell software model, transmitter coil with TDK

PE22 ferrite materials, the receiver coil choose Fair

Rite Material 44 ferrite materials of the company.

The coil with ferrite shielding and coil without

ferrite shielding are compared, and the simulation

can be seen from the simulation results in table 1

compare, with ferrite shielding winding capacitance

value increased significantly, coupling coefficient

between coil was improved, too.

Table 1: Results comparision μH.

Project Inductance simulation

Accept the coil D1 No ferrite 19

Accept the coil D1 Have a ferrite 29.3

Receiving coil D2 No ferrite 10.2

Receiving coil D2 Have ferrite 21.10

Electromagnetic Induction Wireless Power Transmission Efficiency Research

501

Speech De-noising based on Wavelet Transform and Genetic Algorithm

505

Using software Maxwell model, give a

transmitter coil plus the sine voltage of 12 V, set the

transmitter coil pure impedance is 0.03 Ω,

transmitter coil inductance for 30μH, pure

impedance of receiver coil is 0.3 Ω receiving coil

inductance for 20μH.To analyze the impact of

various factors on the transmission efficiency,

software simulation using the control variable

method. Constant when the choice, according to the

actual application situation, first determine the

receiving coil diameter D is 60 mm, after many

experiments, the other parameters constant finally

selected as shown in table 2.

Table 2: Model parameters.

project Constant value range

Accept coil D1 60 mm -

Transmitter coil

60 mm 30mm-90 mm

Coil radial

dislocation S

0 -10 mm -10 mm

Coil axial spacing

0 0-15 mm

The coil number of

turns N

30T 25T-35T

The input voltage

frequency f

150kHz 50 kHz -300 kHz

Load RL 10Ω 1Ω-70Ω

4 THE EXPERIMENTAL

RESULTS

The experimental results are shown in figure 2 ~ 7

Figure 2: Efficiency - coil spacing L.

Coil can be seen from the figure 2 power

transmission efficiency increases with coil distance

L fell quickly, when the spacing of 5 mm, only coil

joint efficiency of 30%.

Figure 3: Efficiency - coil spacing L.

As you can see from figure 3, when fi is less than

100 KHZ, efficiency as the fi and improve, when fi

is greater than 150 KHZ, basic as fi lower and lower

efficiency.

Figure 4: Efficiency - coil spacing L.

You can see from figure 4 efficiency as the coil

number of turns N increases.

Figure 5: Efficiency - coil spacing L.

Can see from figure 5, when the offset r coil

diameter of 0, the receiver and the transmitter coil

equal size, maximum efficiency.

ISME 2015 - Information Science and Management Engineering III

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ISME 2015 - International Conference on Information System and Management Engineering

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Figure 6: Efficiency - coil spacing L.

Can see from figure 6, when the load RL is 10 Ω

reach maximum efficiency.

Figure 7: Efficiency - coil spacing L

From figure 7, you can see that the transfer

efficiency is very sensitive to the radial dislocation,

the efficiency of the radial dislocation is 5 mm is no

radial position only mistake efficiency 47%.

5 CONCLUSIONS

According to above the results of simulation

analysis, to improve the efficiency of wireless

charging device, should try to shorten the transmitter

coil and the receiving coil axial spacing, the coil as

close to as possible, to control the equipment at the

same time, the working frequency of frequency

range between 100 KHZ to 150 KHZ. In the

conditions allow, as far as possible increase the coil

number of turns; Receiving coil and the transmitter

coil diameter should be equal or close, under the

condition of the simulation, the applicable load for 6

Ω~15Ω, can only meet the demand of small wireless

charging devices; Because the efficiency is sensitive

to the radial dislocation, all must be fixing the

transmitter coil and the location of the receiver coil.

Since the establishment of wireless charging

Union (WPC), wireless charging technology has

been paid more and more attention, how to improve

the efficiency of wireless charging, especially to

improve the efficiency of large power wireless

charging is still a very difficult task (Zhang Bao

Qun, Li Xiang Long, 2015). In this paper, some

suggestions are put forward to improve the

transmission efficiency from the angle of the

electromagnetic induction coil coupling. The

research on the large power promotion will be the

next research direction.

ACKNOWLEDGEMENTS

The authors acknowledge the financial Supported by

a project grant from Huaian technology bureau

(Grand No.HAG2014007).

REFERENCES

Wu Junyong, Wu Jiaxun, Zhang Ning, et al. [J]. 2012.

Experimental study of wireless energy transmission

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Wu Ying,Yan Luguang,Xu Shangang. [J] 2003.A New

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Guo Huiping, Liu Xueguan. [M].2007 Electromagnetic

field and electromagnetic wave, Xi'an Electronic and

Science University press, Xi'an. In chinese

Shen Na,Li Chang Sheng,Zhang He. [J].2012.Modeling

and analysis of wireless power transmission system

based on magnetic coupling resonance.Chinese

Journal of Scientific In.strnment．In chinese

Zhang Bao Qun ， Li Xiang Long. [J].2012.Current

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