At present, more than 500 types of devices are using wireless charging and somehow it became a trend. If you had purchased a smartphone recently, you can be able to use this piece of technology. If you are using a sonic toothbrush, it is fed with wireless power when placed on the charging pad. Also, the Apple AirPods are fed power when it is placed in its charging case. Have you ever wondered, how does current flow through the air! Is that a kind of electrical magic? Well, Yes. You will get to know each and every detail and standards used in wireless charging through this article.

Charging Resources
Standards of Wireless Transmission
Inductive Power Transmissions
Coils used in Inductive Power Transmission Systems

So, before going further into this article, we shall see some basic physics laws related to electric current.

Faraday’s Law: When a permanent magnet is passing through an area bounded by the coils, magnetic flux is generated. The electromagnetic field is proportional to the rate of change of the magnetic flux. The wireless charging technology follows similar to this kind of law.

History of Wireless Charging

The concept of wireless power transfer was done by radio waves. But it was just an attempt by James C.Maxwell in 1864. Then in a later period, the famous “Tesla Tower” was built by Nikola Tesla as he believed that he can attempt power transfer. The tower was a giant 200 feet coil with a ball of 3 feet in diameter. However, that experiment failed due to the power dissipation in all the directions. Most scientists were using microwaves and radio waves as a medium for the wireless power transfer. Later comes the inductive charging in which so many research were there on powering Electric cars and buses. The inductive charging method became so famous and used for commercial purposes.

Charging Resources

Energy Harvesting Sources- Light, Magnetic, Vibration. Thermoelectric and Radiofrequency
Renewable Energy Sources – Water, Wind, solar
Power Grid Sources – Inductive Charging, Grid, Capacitive Charging, High Power Grid

Types of Wireless Charging:

Inductive-The coils are used here as transmitter and receiver which are distanced by 0.7 cm. It is the most widely used product in the market.
Magnetic Resonance – it is same as Inductive charging, but the transmitter can charge at the distance of 4.5 cm
Radio Frequency – it is used for charging the devices which require less power.

Standards of Wireless Charging

Wireless Power Consortium- (Qi) – It is an inductive technology which has a frequency of 200 KHz with 5W transmitting power and 5mm maximum range. The Qi is becoming more popular and recently Apple used this standard for its new iPhone8 and iPhone X.

Inductive Power Transmissions

There are two coils of wire L1 and L2, the power is transferred between them by magnetic field. L1 is the transceiver coil and L2 is the receiver coil, both together act as transformers. The AC current is given to the coil L1, creates a magnetic field by Ampere’s Law. Then the magnetic field is passed through the coil L2, it induces an alternating EMF by Faraday’s Law of induction which creates AC in the coil L2. The Alternating Current may drive the load directly or may be converted to Direct Current by the Rectifier.

IPT System Losses

In Coil- Copper loss, Ferrite Core coil loss, Coil Geometry and Radiation loss.
User- Misaignment of the coil
Electronic Circuit- Component loss, Resonance

Coils Used in Inductive Power Transfer (IPT)

1. Ferrite Core Coils :

The Ferrite-Core coil consists of coil cores and 1-2 layers of transmitter core and receiver core. The Absorption takes place at the transmitter coil and the Reflection takes place at the Sending coil. Copper, Stainless steel or Aluminium is used as Ferrite core coils. The magnetic field is concentrated near the core coil, can increase the circuit temperature, high permeability.

2. Air core Coils

The Air-Core coil has uniform flux density propagation with a simple structure. It has low permeability, no core losses and low efficient in the low frequency applications. No core loss, since it has no core present.

Advantages of Wireless Charge Transfer

• Security
• Design
• Free Positioning
• Easy
• Portable Pad
• Sometimes parallel charging for multiple devices
• Can reduces electric shock

Disadvantages of Wireless Charge Transfer

• The time taken for charging the device is more
• Can’t predict the battery life
• High cost
• Energy losses and Heat effect
• System complexity

Future of Wireless Charging

At present, lot of money spent on prototypes and ongoing research on this topic. Many companies have upgraded their mobile phones and devices to wireless charging and also in many public places like Coffee Shops and airports have this wireless charging facility. From a small Electric toothbrush to a modern Electric Car, the wireless charging plays a vital role in the industries and manufacturing sectors. Not even from IPT, but also from Radio, Laser, Microwaves, the wireless power transmission can be done.