Wireless Charging Technology
Wireless electric vehicle charging stations (WEVCS) technology is charging an electric car without involving cables that are directly related to the vehicles system. Wireless charging is done without a connector. The location of wireless charging is called a wireless electric vehicle charging station. There is no plug on WEVCS like charging in standard EVCS. Wireless electric charger technology for electric cars is a recent development for charging batteries. The basic principle of an electric car charging or wireless charger system is the same as the working principle of the transformer. One of the advantages of wireless charger is that charging an electric car (vehicle) becomes safer and more convenient for users.
Short Working Principle
If the transformer has a primary and secondary side, then charging without WEVCS cable has a transmitter side and a receiver side. If the transformer has a primary (coil) winding and secondary winding, the wireless charging of an electric car also consists of a transmitter winding and receiver winding.
However, wireless charging of electric cars changes the parameters of alternating current (AC) from low frequency 50Hz to high frequency, where it does not occur in the transformer. High-frequency AC power is supplied to the transmitter coil, then the alternating magnetic field is formed. This field then induces the receiver winding so that a voltage appears on the receiver winding. This voltage is used to charge the vehicle battery.
The most important thing in wireless charging or wireless charging to remain efficient is to maintain the frequency of resonance between the transmitter and receiver. In order for the resonance frequency to be maintained, compensation networks are added on both sides.
Early History of Wireless Charging
Wireless charging technology was initiated by Nikola Tesla’s research around 1891. At that time he made the Tesla coil. The aim of his research is to develop a wireless power transmission system (wireless). Tesla then built the Wardenclyffe Tower as a high-capacity, high-capacity wireless energy transmission station. Unfortunately, the tower was dynamited and destroyed on July 4, 1917.
Static and Dynamic Wireless Charging
Based on the application, wireless electric vehicle charging stations cars can be divided into two categories,
- Static Wireless Charging
- Dynamic Wireless Charging
Static Wireless Charging
This wireless charging is also called a static wireless charging station (SWCS). As the name suggests, the car battery is charged when stationary (stops). We can park the vehicle in a parking lot or in a garage that is combined with a wireless charging station. The transmitter is installed underground while the receiver is mounted under the vehicle. Charging is done by aligning the transmitter with the receiver and then silenced so that the charging or charging process takes place. The duration of wireless charging depends on:
- Large AC power supply
- Distance between transmitter and receiver
- The size of the cushion.
Wireless charging of this SWCS electric car is best built in an area where the car is parked for a certain time interval.
Dynamic Wireless Charging System
Wireless charging is also called dynamic wireless charging station (DWCS). As the name suggests, wireless charging or wireless charging can be done while the car is running. Power is transferred through the air from the stationary transmitter to the receiver winding of the moving vehicle. Wireless charging technology allows car mileage to be further away. Because, the battery is charged continuously during the trip. This reduces the need for a large car battery capacity so as to reduce the weight of the car. Reducing the load will further distance the mileage.
Types of Wireless Charging Electric Cars
Based on its operations, wireless electric vehicle charging stations (WEVCS) can be classified into four types
- Wireless Charging Capacitive (CWCS)
- Wireless Charging Permanent Magnetic Gear (PMWC)
- Inductive Wireless Charging (IWC)
Capacitive Wireless Charging
Charging wireless or wireless charging electric car type CWCS is done by using a displacement current due to variations in the electric field. Instead of magnets or winding as transmitters and receivers, coupling capacitors are used here as wireless power transmissions. The AC voltage is first supplied to the power factor correction circuit aimed at increasing efficiency, maintaining voltage levels and reducing transmission losses. Then it is supplied to the H-bridge for the generation of high frequency AC voltage. This high frequency AC applied to the transmission plate causes the development of an oscillating electric field then causes a displacement current on the receiving plate through electrostatic induction.
The receiver’s AC voltage is converted to DC then charges the battery via BMS by a rectifier circuit and filter. The frequency, voltage, size of the clutch capacitor and the air gap between the transmitter and receiver affect the amount of energy transfer. The operating frequency is between 100 to 600 kHz.
Wireless Charging Permanent Magnet Gear
In this wireless charging technology for electric cars, each transmitter and receiver also consists of armature windings and permanent magnets synchronized inside the winding. The principle of operation of the transmitter side is similar to motor operation. When we apply AC current to the transmitter, it will cause mechanical torque on the transmitter magnet to cause its rotation. Due to changes in the transmitter’s magnetic interaction, the PM field causes torque at the PM receiver which results in rotation in sync with the transmitter magnet.
Now the change in the receiver’s permanent magnetic field causes the production of AC current in the winding, that is, the receiver acts as a generator as an input of mechanical power to the receiver’s PM which is converted to electrical output at the receiver’s winding. Rotating permanent magnetic clutch is called magnetic gear. AC power generated at the receiver side is fed to the battery after repairing and filtering through the power converter.
Inductive Wireless Charging
The basic principle of wireless charging or wireless charging of electric cars is Faraday’s induction law. Here, wireless transmission is achieved by inducing a magnetic field between the transmitter coil and the receiver. When the main AC supply is applied to the transmitter coil, it creates an AC magnetic field that passes through the transmitter coil and this magnetic field moves electrons in the receiver winding causing AC power output. The AC output is repaired and filtered and then fills the car’s energy storage system. The amount of transfer on the electric car charger depends on frequency, mutual inductance and the distance between the transmitter and the receiver coil. The operating frequency of wireless charging IWC electric cars is between 19 to 50 kHz.
Resonant Inductive Wireless Charging
This wireless electric vehicle or car charger station is basically a resonator with a high quality factor transmitting energy at a much higher rate. Because it operates at resonance, even with weaker magnetic fields, we can transmit as much energy as transfer capacity as at IWC. Power can be transferred remotely wireless. Maximum power transfer through the air occurs when the winding of the transmitter and receiver is adjusted so that the frequencies of the two resonant coils must match. So in order to get a good resonance frequency, an additional series-parallel combination compensation network is added to the transmitter and receiver coils. The additional compensation network on this electric car charger must adjust the increase in resonant frequency while also reducing additional losses. RIWC operating frequency is between 10 to 150 kHz.
- Types of Electric Cars and Working Principles
- Electric Car Components and Functions
- Electric Car Batteries and Characteristics
- Electric Vehicle Charging Station (EVCS)