High-Frequency Wireless Power Transmission by Resonant Inductive Coupling

Introduction:

Wireless Power transmission is the transfer of electrical power from a power source to an electrical load without using discrete man-made conductors. The reason for going to wireless power transfer system is to provide reliable power transmission at low cost and to make life more comfortable. This wireless power transmission system is completely Eco-friendly and efficient. Just imagine the future with wireless power where in there will be no need of power cables and no need to plug in the electrical devices to the electric sockets for charging which brings a profound change in the society. The core technology used in the wireless power transmission system is Inductive coupling through magnetic fields. An Impedance compensating circuit is also used to achieve maximum power transfer. The core technology is similar to those found in transformers, except primary and secondary winding are physically separated and tuned to resonate for increasing their magnetic coupling. These magnetic field generated by the primary coil is arranged to interact vigorously with matched secondary winding where the load is connected.

In recent days, global scenario has been changed a lot and there is tremendous development in every field particularly in electrical field. If we don’t converge our innovative ideas for the development of new power technologies we may face a decreasing trend in the development of power sector. The transmission of power without wires may be one excellent alternative for electricity transmission. This remarkable discovery of wireless power and its core technologies even in present day system are based on Dr.Nikola Tesla’s contribution in the field of all wireless systems. This shows us that he is indeed the “Father of Wireless systems”. The most famous Wardenclyffe tower in Colorado Springs (Tesla tower) also called as “Magnifying wireless transmitter” was designed and constructed by Dr.Nikola Tesla which used Ionosphere to transmit the electrical power all over the earth. The Colorado Springs was commonly known for its Geo-Magnetic activates where Dr.Nikola Tesla built his laboratory, in the center of the lab he built a massive transformer with primary of the transformer was grounded and other end was raised at a great height. This transformer produced a voltage of several million volts at a frequency of 150 thousand hertz which created a man-made lightning which was 40m long. The tower frame was 57m long with a steel shaft that dipped into the ground and a huge copper hemisphere which worked as a powerful amplification transmitter was installed at the top of the huge tower. With this Dr.Nikola Tesla was able to lit 200 electric bulbs in a radius of 25 miles from the tower. The core technology he used was “The currents transmitted by high frequency standing wave energy”. With this technology, the power would be transmitted across large distances with negligible losses. But this was an unfortunate incidence that people of the century was not in a position to recognize his splendid work. He is well known as “scientist ahead of time”. Otherwise we may have transmitted electricity wirelessly and would have converted our mother earth a wonderful adobe full of Electricity.The figure 1 shows tesla tower and figure 2 shows the image of Nikola Tesla.

Statement of the Problem:

Today, the average individual has a different charging cord for every device he or she owns. This can be unwieldy, create space constraints and not be quite aesthetically pleasing. Imagine a future where wireless power is feasible, whereby devices can be charged without the need for cords thus freeing us from those ubiquitous wires.

Block Diagram of Wireless Power Transmission:

The Wireless Power Transmission system consists of a power source which is a high-speed switching circuit for generating high frequency signals, primary impedance compensating network and primary magnetically coupled coil; all these components put together to form transmitter circuit. And receiver circuit comprises of secondary magnetically coupled coil, a secondary impedance compensating network, a high frequent rectifier, a voltage regulator and a DC load.

The high-speed switching circuit is a high frequency resonant inverter that comprises of power MOSFETs and gate triggering circuits. A power MOSFET is a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) designed to handle significant power levels and can operate at high frequencies in the range of hundreds of kilo Hertz. With the advancement in the field of power electronics a new power MOSFET (SiC MOSFET) that can operate at frequencies up to Mega Hertz which is used for high frequency switching applications. The impedance matching network has a significant role in Wireless Power Transmission system. The impedance matching network reduces the VA (volt-ampere) rating of the power source by minimizing the reactance of input impedance and increase the power transmission efficiency by utilizing the magnetic field resonance. The time varying magnetic field is generated from the primary coil and is transmitted to the secondary coil. A high frequency rectifier is used to convert high frequency AC power into a DC power. There are two losses associated with the diodes in a high frequency rectifier; losses due to the forward conduction of the diodes and the high frequency loss according to the switching time of the diodes. These losses act as the reverse recovery time for the diodes. To eliminate these losses, Schottky diodes or ultrafast diodes are used in the rectifier circuit instead of normal 1N4007 diodes. The voltage regulator is used to stabilize and control the DC voltage level according to the required load voltage. 

Applications of wireless Power technologies:

Wireless power transmission is used to power electrical devices in case where the interconnecting wires are inconvenient or hazardous. Wireless electricity can eliminate frequent plugging in of devices to the electrical sockets and provide an efficient way to transmit the power to the moving parts where electricity can’t be reached through wires. Wireless Electricity finds its application where ever we use electrical loads like mobile phones, laptops, electric vehicles and all other domestic electrical utilities. It can also bring more and more electrical Vehicles on road by putting them under wireless electricity. This Technology can provide a convenient safe and flexible means to charge electric appliances.

Wireless power transfer in electric vehicles may bring a profound change in the charging system. Plug in Electric vehicles need cables & Plug charges but physical plug charges and Cables may become hassle and messy. With the system where we have to physically plug in chargers, there are number of occasions where the owners can often forget to charge the vehicles. For stationary applications like charging of plug in electric vehicles at home, Wireless transmission technology adds a convenient factor compared to actual plugging in. which means the vehicle will have full charge every morning. By re-configuring the transformer and altering the resonant frequency energy is transferred to the battery with lower energy losses. Sufficient power for the battery can be transferred from the primary to secondary circuit without significant energy losses. The electrical power is then transmitted to the battery which is electrically coupled to the secondary circuit through the air core transformer.

Dynamic charging in simple words mean charging of the electrical vehicles even under the movement in electrically equipped roads. In larger cities dynamic charging offers an even greater impact utilizing existing infrastructures as vehicles travel along the busy freeways wireless charging can also occur while the vehicle is in motion. The transmitting plate kept under the road will be ON only when the vehicle passes over the plate (the vehicles having receiving plate comes into area of transmitting plate it turns on) this is known as segment control technology. The power lines are managed by Segment Control Technology, which supply power to the vehicle only when it is passing over the power line. This technology prevents a magnetic field from being generated while pedestrians walk or other vehicles run on the road as well as wasting of energy. Dynamic charging allows electricity to supply a very large fraction of the energy for the transportation sector and reduce considerable petroleum consumption. Previously traffic delays now provide of charge while passing over in motion charges. Rain does not affect the charging capability and the transmitting circuit.