Design and Analysis of Wireless Power Transfer Charger for Electric Vehicles

Majdi EL Fahem   .   July 28, 2022

What is Behind the Wireless Power Transfer (WPT)?

In simple terms, wireless power transfer is the transmission of electric power without any direct physical wire or cable connections. The power transfer is usually based on the technology that utilizes electric, magnetic, or electromagnetic fields. WPT happens by creating an alternating magnetic field on the transmitter coil. This magnetic flux is then converted into an electrical current in the receiver coil.  The generated electrical current depends on the amount of flux generated by the transmitter coil, and how much of a percentage the receiver coil can capture. The distance, size, and position of the receiver coil relative to the transmitter coil decide the “coupling factor or coupling coefficient” of the two coils.

Ever since the concept of WPT became popular, scientists and engineers begins to develop various techniques to realize this concept. These techniques are mainly classified based on the transmission distance, maximum power, and method used to achieve power transmission. Therefore, WPT can be categorized into the inductive coupling, capacitive coupling, magnetic coupling, and electromagnetic radiation. Moreover, based on the energy encryption and WPT technique, broadly we can divide it into three sections such as near field, medium field, and far field. The comparison among these techniques, their advantages - disadvantages, and applications are tabulated below.


 

 
Comparison between Near, Medium, and Far Fields of WPT [1]
AspectThe Near FieldThe Medium FieldThe Far Field
  The Energy EfficiencyHighHighLow
  The Performance of power transferHighHighLow
 The characteristics of distance, frequency, and number of turnsEasier to transfer powerEasier to transfer powerMore complex to transfer power


 

Advantages and Disadvantages of WPT Techniques [1]
WPT techniqueAdvantagesDisadvantagesApplications
  Inductive Coupling Simple safe, high efficiency in short range  Short transmission distance, needs accurate alignment  Electric toothbrush and razor battery charging, induction stovetops, and industrial heaters
  Capacitive Coupling  Simple structure of couplings, lightweight, low cost, position flexibility, and high frequency  Small power density of the small coupling capacitance  Charging portable devices, power routing in large-scale integrated circuits, Smartcards
  Magnetic Resonant Coupling  Long transmission distance, no radiation  Difficult to adjust resonance frequency for multiple devices  Cars charging
  Electromagnetic Radiation  Very high transmission percent over long distance  Radiation needs line of sight  Implement in biomedical
 

 

 
 

Why WPT is in High Demand?

  • Fewer wires and connectors
  • Lower risk of sparks
  • Ability to charge cars while they are inroads
  • Convenient, safe, and effective way to transfer power
  • Environmentally friendly - Does not harm or injure a human or any living being.
  • Enhancing the quality of life and reducing the risk of infection and other complications caused by maintenance or replacement of implantable medical devices
 

What are their Drawbacks?

  • Low efficiency and higher losses
  • Expensive
  • Higher maintenance costs
  • Not suitable for high power delivery.
  • Power drastically decreases with misalignment and higher air gap distance. 
 

How Can FEA Simulation Help in Designing an Efficient WPT of an Electric Car?

The graph below shows the main design issues that an engineer needs to tackle while designing and developing a wireless power charging system for electric vehicles. The same graph demonstrates how EMWorks solution can be used to solve these problems. The main key parameter of a WPT system is the coupling coefficient which is affected mainly by the distance and the alignment of transmitter and receiver. It is also impacted by the geometry of these coils. Different scenarios and designs can be investigated to come up with an efficient design iteration that provides higher transmitter energy. Resonant wireless power transfer is a considerably great solution to improve further the efficiency of the charging system. 
Through their different magnetic modules, with parametric and multi-configuration features, EMWorks software help to test and solve different iterations and design scenarios. In addition to this, the circuit simulator of EMWorks tools is used to model the power system including different resonant circuit topologies and loads to provide better efficiency and performance of the WPT charger. 

 
 

 
Wireless Charger of an Electric Vehicle
 
 

 
Smartphone Wireless Charger