The major objective of this project is to build up a device for wireless power transfer. The concept of wireless power transfer was realized by Nikolas Tesla. Wireless power transfer can make an extraordinary change in the field of the electrical engineering which eliminates the use of conventional copper cables and current carrying wires. Based on a concept, the project is developed to transfer power within a small range. The power is transferred without any connection. This project can be used for charging batteries those are practically not possible to be connected electrically such as pace makers implanted in the human body which runs on a battery or mobile phones. The patient is required to be operated every year to substitute the battery. This project is intended to charge a rechargeable battery wirelessly for the purpose. Since charging of the battery is not possible to be established, we are providing a DC fan that runs through wireless power.
This project is built by means of an electronic circuit which converts AC voltage to High frequency AC voltage. The high frequency AC voltage is given to a coil forming as primary of an air core transformer. The secondary coil develops a voltage of high frequency. Thus the transfer of power is done by the primary (transmitter) to the secondary that is separated with a considerable distance. Therefore the transfer could be seen as the primary transmits and the secondary receives the power to run load.
Electronic transformer mechanism is based on half wave bridge rectifier and double the line frequency operation. The AC power from the device is given as an input to the bridge rectifier where it is converted into DC through resistor capacitor network. In one half cycle transistor (collector to emitter) starts conducting, the transformer primary feedback windings provide biasing for the transistor. Current flows from one end to other of primary coil and then it passes through a capacitor and reaches ground. In another half cycle other transistor (collector to emitter) starts conducting and then the current flows in the other capacitor. So in one half cycle the flow of current is from two ends of the primary windings, in another half cycle flow of current is from secondary windings. Biasing of both the transmitter are done automatically i.e. we can’t say that when which coil gets bias. So current flowing in the primary coil in both half cycles generates A.C in secondary coil. As the transistors are fast switching devices frequency of A.C becomes high.
Voltage induced in secondary winding coil is fed to a bridge rectifier that delivers pulsating dc which is then filtered by an electrolytic capacitor. The filtered dc being unregulated a regulator is used to get a constant voltage irrespective of changing input dc.
The regulated dc voltage is further filtered by a small electrolytic capacitor of high frequency for any noise which is generated by the circuit which can be used for battery charging. The DC voltage is used for other applications as on when required. The output of bridge rectifier is taken to drive the DC Fan.
COMPONENTS USED IN THE CIRCUIT:
Input power supply: AC source of 230V 50Hz
High frequency transformer
+12V DC fan
A set of diodes for the bridge rectifier arrangement
DC rectification and filter
A capacitor for the filter circuit
A set capacitor for the filter circuit
The above block diagram
represents as to how the wireless power transfer takes place. There are power
supply section, rectification and regulation sections.
Power supply of AC 230V,
50Hz is fed to the transformer block. The transformer block is consisting
of AC to DC rectifier and a filter circuit which filters out the ripples from
the rectified DC to safer low DC supply. The output of this is fed to an
inverter which performs very fast switching action and the resultant is the
high frequency AC voltage which is fed to the primary coil . This AC voltage
induced in the secondary coil is rectified and filtered to get the output DC
voltage which is given to power a small fan. The regulated voltage of 5V is
also available after regulating the DC voltage using a regulator.
HF-Transformer, HF-diodes, rectifier, Transistors, Two air filled inductor coils, Voltage regulator, BLDC fan.