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 CHEMICAL ENGINEERING TRANSACTIONS  
 

VOL. 59, 2017 

A publication of 

 

The Italian Association 
of Chemical Engineering 
Online at www.aidic.it/cet 

Guest Editors: Zhuo Yang, Junjie Ba, Jing Pan 
Copyright © 2017, AIDIC Servizi S.r.l. 
ISBN 978-88-95608- 49-5; ISSN 2283-9216 

Magnetic Coupling Performance Analysis and Simulation of 

ICPT Landing-type Pickup Mechanism 

Baodi Hong, Lijun Gao., Yong Zhang, Zheying Zong* 

Department of Mechanical and Electrical Engineering, Inner Mongolia Agriculture Universit, Huhhot 010018, China 

ZheyingZong@126.com 

Magnetic energy conversion mechanism simulation model of contactless energy transmission system has 

been set up based on Maxwell 3D simulation environment. According to the model, the influence of primary 

and secondary- side coil position of loosely coupled transformer on contactless power transmission system 

and the influence of primary and secondary- sided coil position on the system apparent power, transmission 

power and system transmission efficiency have been analyzed with utilization of experimental and ANSYS 

finite element simulation software. Feasibility of the above simulation calculation has been verified through 

experiments. Simulation and experimental results show that mutual inductance coupling is affected by the 

above factors, providing a theoretical basis and guidance for design of landing- type scaffolding pickup coils. 

1. Introduction 

Inductively Coupled Power Transfer ICPT (Inductively Coupled Power Transfer) is defined as power transfer in 

the form of wireless by space magnetic field from the primary side coil to vice side coil also called pick-up 

mechanism. The existence of air magnetic circuit of the magnetic coupling mechanism result in larger leakage 

inductance of the system. Bigger air gap between pick-up coil and transmitting terminal leads to lower 

coupling coefficient, larger size of the coupling mechanism and higher costs. In order to improve power 

transmission efficiency, The following measures can be taken: 1) High frequency alternating current is injected 

into launching terminal; 2) The resonance compensation is taken between launching terminal and pick-up 

terminal; 3) Shorten the distance between pick-up mechanism and the transmitting coil, to improve the 

coupling coefficient (Wang, 2014; Qin, 2010; Su, 2013). Traditionally, the larger distance between fixed pick-

up coil used in electric car and the transmitting rail (20 ~ 30 cm) leads to the lower coupling coefficient, the 

larger size of the coupling mechanism and the higher cost. For this, through the use of landing-type 

scaffolding coil, as shown in figure 1, minimize air gap of coupling mechanism is to improve mutual inductance 

and magnetic coupling transmission efficiency (Dong, 2016). 

 

Figure 1: Wireless charging schematic diagram of landing- type scaffolding pick-up coil 

2. System Main Circuit 

The system main circuit of Wireless power-supply electric vehicle consists of the following three parts: electric 

energy conversion device in transmitting terminal, electromagnetic coupling mechanism, electric energy 

                               
 
 

 

 
   

                                                  
DOI: 10.3303/CET1759136

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Please cite this article as: Baodi Hong, Lijun Gao, Yong Zhang, Zheying Zong, 2017, Magnetic coupling performance analysis and simulation 
of icpt landing-type pickup mechanism, Chemical Engineering Transactions, 59, 811-816  DOI:10.3303/CET1759136   

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conversion device of vehicle side. The transmitting terminal by rectification, filtering, voltage stabilization, high- 

frequency inverter converts Power-frequency AC into high-frequency AC send it into electromagnetic coupling 

mechanism, the circuit structure is shown in figure 2. In the circuit model, capacitors work as compensation of 

the original coil and deputy coil. 

 

Figure 2: Power transmission system main circuit structure diagram 

Because the original side compensation capacitor is neither affected by the coils coupling coefficient, nor by 

vice edge quality factor Q, and reflection impedance of vice side of series compensation topology structure on 

the former side appears pure resistance, and the influence of the load variation on the former is relatively 

small and make it work in resonant state, finally this improve power transmission capacity of the system, 

reduce the input volt-ampere rating. Therefore, the original edge series compensation topology structure as 

shown in figure 3 is employed to realize the high-power electric power transmission. 

 

Figure 3: SS topology structure diagram 

3. The relation between mutual inductance coefficient and the relative position of the 
original coil and vice coil 

Design experiment circuit as shown in figure 4 to simulate magnetic coupling mechanism of ICPT system, the 

system working frequency and the input voltage is set to a fixed value, actually they can be controlled by 

feedback. The formula estimating Exciting current is 𝑉𝑎𝑐 ∙ 𝐼𝑝 ≈ √(𝑃𝐿
2 + (𝑄𝑃𝐿)

2), value of Q is 3 to 6 (He, 2007). 

By Open circuit voltage method (Liu et al., 2012) mutual inductance is measured, M =
𝑈𝑜

𝜔𝐼1
, (𝑈𝑜- open circuit 

voltage and 𝐼1-no-load current) two coil parameters are shown in table 1.The loose coupling transformer 
employs EI-type, the vertical motion of E type iron core coil imitates drop of stents, level motion simulates 

mobile location. By ANSYS the inductance value is calculated of the former and vice  

 

Figure 4: Schematic diagram of pickup coil and transmitter 

Assume that loop L1 and loop L2 carry steady current I1 and I2 respectively, model of different thickness of air 

gap of loosely coupled transformer are set up. Calculate mutual inductance values of 4 set of magnetic 

coupling mechanism, the longitudinal distances of which are 4 cm, 9 cm, 12 cm, 15 cm, 18 cm respectively, 

and then horizontally move 2 cm, 6 cm, 8 cm, 10 cm with longitudinal distances fixed. 

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Table 1: Parameters of transmitter coil and pickup coil for experiment 

 

     

Figure 5: Variation curves of mutual inductance M changing along with primary and secondary side distance X 

and lateral motion Y 

 

Figure 6: Maxwell magnetic coupling simulation 

The figure 5 shows that with the increase of air gap distance X the mutual inductance parameter and coupling 

degree decay quickly, significantly reduce, so the inductance parameters are greatly influenced by gap 

thickness.  

The mutual inductance between two adjacent circuit is determined by the circuit size, shape and relative 

position (Liu et al., 2012) in magnetic simulation environment of Maxwell's 3D (Hoang et al., 2012) mutual 

inductance simulation of contactless power transmission system, magnetic energy conversion mechanism, is 

done as shown in figure 6, model sizes are shown in table 2. 

Table 2: Parameters of transmitting coil and receiving coil for simulation 

Coil size Coil material self-inductance Exciting current height 

Transmitting coil 

Receiving coil 

copper40mH 100A 80mm 

copper 20mH 20A 10mm 

 

The loose-coupled transformer model a transmitting coil and pick-up coil is set up as follows: 

Figure 8 shows that when the air gap is not very big, with the increase of air gap, the coupling coefficient 

reduced greatly; when the air gap increases to a certain degree, the extent of coupling coefficient decreases 

slowly; when the I type iron leave away coupling coefficient decreased to minimum value 0.55. The results of 

simulation and experimental results are consistent. 

 

Coil Size (cm) Iron core Number of turns Self- Inductance (μH) Nominal voltage 

Transmitting coil 

pick-up coils 

100×200 

120×90×20 

be 

be 

5 

10 

80 

65 

220V 

220V 

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Figure 7: Steps and process to build a simulation model                 Figure 8: Simulation results  

4. The relation between inductance parameters and the transmission efficiency of the 
system 

Non-contact transformer coupling tightness can be described by the mutual inductance value and the coupling 

coefficient, the model is shown in figure 3, Rp and Rs stand for behalf transmitting coil and receiving coil 

resistance, M is the mutual inductance between the two coils, UAC is the equivalent ac power on the 

transmitting coil, and RL is the equivalent load impedance. 

AC p p p p s

p

1
U =I R +I j(ωL - )-I jωM

ωC

  (1) 

𝐼�̇�𝑗𝜔𝑀 = 𝐼�̇�𝑅𝑠 + 𝐼�̇�𝑗(𝜔𝐿𝑠 −
1

𝜔𝐶𝑠
) + 𝐼�̇�𝑅𝐿 Transformer is in a resonant state, the resonant frequency is: 

0

1 1

p p s s
L C L C

   
 

2 2

( )

( )

s L AC
P

s L P

R R U
I

R R R M




 

 
2 2

( )

AC
s

s L P

j MU
I

R R R M






 

 (2) 

The resonant reflecting impedance and the transmission efficiency of the system are: 

2

0
( )

r

s L

M
R

R R






 
2 2

02

2 2 2

1 0
( ) ( )

L

p L s L S

M RP

P R R R M R R





 

  

 (3) 

System of transmission efficiency ƞ and system parameters 𝜔0,𝑅𝐿,𝑅𝑃,𝑅𝑆 and the mutual inductance M, M is 
proportional to the working frequency and the load resistance and inversely proportional to the transmitting coil 

resistance and receiving coil resistance. 

Entering the following parameters: the working frequency 𝑓0 = 40𝑘𝐻𝑧, load resistance 𝑅𝐿 = 3𝛺, the original 

side coil resistance 𝑅𝑃 = 0.25𝛺, vice side of coil resistance 𝑅𝑆 = 1𝛺, mutual inductance M = 20μH into formula 

(3), the results are shown in figure 7. 

5. The relationship between inductance parameters and apparent power 

Because of existence of air gap in ICPT system, larger primary power capacity is needed for power 

transmission, primary apparent power become important parameters. 

Without considering winding resistance and core loss, and load power output is constant, 𝐼𝑆 = √
𝑃𝐿

𝑅𝐿
 according 

to the formula (1), the original voltage and current are: 

2 2
( ) ( )P SL P L

AC

L

L LP L R
U M

R M M
  

 2 2 2
L SL

P

L

R LP
I

R M






 

 (4) 

Get the original winding apparent power: 

2 4
2 2 2 2 2 2 2 2 2 2

2 2
( ) ( )

P AC P

L P L
S P S P S L P S L

L

S U I

P L R
L L L M L L M R L L R

M R






     
  (5) 

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In the case of resonance frequency operation, system input power is minimum: 

2 2

min 2 2 2

(2 ) (2 ) 2
( 1)L P s L

P L

P L L M P k
S P

M k k

 
   

 (6)  

The apparent power of original coil is only related to coupling coefficient k and the output power PL. If the 

coupling coefficient and the output power are constant, the minimum input apparent input power is determined. 

When the coupling coefficient increases, the system input apparent power decreases (Kacprzak et al., 2005; 

Mecke and Rathge, 2004). 

Apparent power increasing rate   is deduced by formula (5): 

P Pmin

Pmin

2 2 2 2 2 2 2 2 2

2

S S
Δ

S

(1 k) / ( 1 ) (1 k ) 1 (1 k )( 1 ) /
1

2 k

L S S L
R L k L k R 




       
 



 

Table 3: The influence of coupling coefficient on apparent power 

Apparent power increasing rate   1 2 2.5 3 3.5 
coupling coefficient 0.25 0.5 0.6 0.7 0.8 

 

Table 3 indicates that under the condition of the same voltage input, with the increase of the coupling 

coefficient apparent power decreases. 

6. The relationship between inductance parameters and transmission power 

Position change of original and vice coils leads to change of mutual inductance, according to the formula (4), 

the change of mutual inductance causes reflecting impedance changes vice side, and influences ICPT system 

resonant frequency and the excitation current, and affects the transmission power of the system (Chen, 2014). 

 As shown in figure 3, vice side current is as shown in formula (8): 

OC
S 2 2

S S S L P P P S L

j MU
I

[j L 1/jωC R R ][j L 1/jωC R ω M /(R R )]



 


      

 (7) 

When the ICPT system works in the natural frequency of resonance system, vice side are in resonant state 

completely, the vice current amplitude is simplified, transmission power is equal to: 

2 2 2

L 0 OC
O 2 2 2

S L P 0

R ω M U
P

[(R R )R ω M ]


 

 0 OC
S 2 2

S L P 0

ω MU
I

(R R )R ω M


 

 

Let 𝑓0 = 40𝑘𝐻𝑧 , load resistance 𝑅𝐿 = 3𝛺  the original side coil resistance 𝑅𝑃 = 0.25𝛺 , vice side of coil 

resistance 𝑅𝑆 = 1𝛺 , mutual inductance M=5,10,15,20,25,30,35,40,45 μH, contactless power transmission 

system is shown in the curve of the relationship between transmission power ƞ% and the mutual inductance. 

7. Conclusion 

1) In SS topology, the presence of air gap of primary coil and secondary coil leads to small mutual inductance 

coefficient, through the design of the movable scaffold, the electromagnetic coupling mechanism to a certain 

extent solves the problem about the worse performance of small mutual inductance.  

When the car passes through the transmission rail coil, pick-up coil downs to below 9 cm off the ground, the 

purpose is to achieve of reducing coupling mechanism air gap and optimizing coupling performance and 

increase mutual inductance, system apparent power will be reduced so as to improve the system transmission 

power and the transmission efficiency and the stability of the output power. 

2) Through analysis of the simulation results compared with the actual values, it is known that by the key 

parameters simulation results of ANSYS software to non-contact electromagnetic coupling transformer 

conform better with the actually measured values. By ANSYS software it is easy to realize the change of the 

transformer model geometry size and parameters, and find out the effect of key parameters of the non-contact 

electromagnetic coupling transformer on its transmission efficiency: Air gap applies the greatest influence on 

the transmission efficiency, which is also the most comprehensive (affecting the transformer magnetic flux 

leakage and coupling coefficient). For ICPT system of wireless-charging electric vehicles, the high frequency 

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resonance and other measures can increase the output power and transmission efficiency of system, and can 

also the use of landing-type scaffold to adjust the distance between the original and deputy coil enhance 

practicability and economy of contactless power transmission system.  

Acknowledgments  

This work is partially supported by Inner Mongolia Department of Education under grant (No. NJZC16058) and 

National Natural Science Foundation of China under grant (No. 11262015). This is gratefully acknowledged. 

References  

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