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.
|Aspect||The Near Field||The Medium Field||The Far Field|
|The Energy Efficiency||High||High||Low|
|The Performance of power transfer||High||High||Low|
|The characteristics of distance, frequency, and number of turns||Easier to transfer power||Easier to transfer power||More complex to transfer power|
|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
- Higher maintenance costs
- Not suitable for high power delivery.
- Power drastically decreases with misalignment and higher air gap distance.