19-10-2016, 04:11 PM
1459933701-AdvancedWPT.docx (Size: 532.25 KB / Downloads: 8)
ABSTRACT
The project is a device to transfer power wirelessly instead of using conventional copper cables and current carrying wires. The concept of wireless power transfer was introduced by Nikolas Tesla. This power is made to be transferred within a small range only for example charging rechargeable batteries etc.
For demonstration purposes we have used a fan instead of battery that operates by using wireless power. This requires an electronic circuit for conversion of AC 230V 50Hz to AC 12V, high frequency and this is then fed to a primary coil of an air core transformer.
OBJECTIVE
To develop the wireless power transfer concept into the realisation of practical application through operation of a 12V fan by a power coil.
INTRODUCTION TO WIRELESS POWER TRANSFER
Wireless power transfer (WPT) or wireless energy transmission is the transmission of electrical power from a power source to a consuming device without using discrete manmade conductors. It is a generic term that refers to a number of different power transmission technologies that use time-varying electromagnetic fields. Wireless transmission is useful to power electrical devices in cases where interconnecting wires are inconvenient, hazardous, or are not possible. In wireless power transfer, a transmitter device connected to a power source, such as the mains power line, transmits power by electromagnetic fields across an intervening space to one or more receiver devices, where it is converted back to electric power and utilized.
Wireless power techniques fall into two categories, non-radiative and radiative. near-field or non-radiative techniques, power is transferred over short distances by magnetic fields using inductive coupling between coils of wire or in a few devices by electric fields using capacitive coupling between electrodes. Applications of this type are electric toothbrush chargers, RFID tags, smartcards, and chargers for implantable medical devices like artificial cardiac pacemakers, and inductive powering or charging of electric vehicles like trains or buses.
OVERVIEW
"Wireless power transmission" is a collective term that refers to a number of different technologies for transmitting power by means of time-varying electromagnetic fields. The technologies, listed in the table below, differ in the distance over which they can transmit power efficiently, whether the transmitter must be aimed (directed) at the receiver, and in the type of electromagnetic energy they use: time varying electric fields, magnetic fields, radio waves, microwaves, or infrared or visible light waves.
In general a wireless power system consists of a "transmitter" device connected to a source of power such as mains power lines, which converts the power to a time-varying electromagnetic field, and one or more "receiver" devices which receive the power and convert it back to DC or AC electric power which is consumed by an electrical load. In the transmitter the input power is converted to an oscillating electromagnetic field by some type of "antenna" device. The word "antenna" is used loosely here; it may be a coil of wire which generates a magnetic field, a metal plate which generates an electric field, an antenna which radiates radio waves, or a laser which generates light. A similar antenna or coupling device in the receiver converts the oscillating fields to an electric current. An important parameter which determines the type of waves is the frequency f in hertz of the oscillations. The frequency determines the wavelength λ = c/f of the waves which carry the energy across the gap, where c is the velocity of light.
Wireless power uses the same fields and waves as wireless communication devices like radio, another familiar technology which involves power transmitted without wires by electromagnetic fields, used in cell phones, radio and television broadcasting, and Wi-Fi. In radio communication the goal is the transmission of information, so the amount of power reaching the receiver is unimportant as long as it is enough that the signal to noise ratio is high enough that the information can be received intelligibly. In wireless communication technologies, generally, only tiny amounts of power reach the receiver. By contrast, in wireless power, the amount of power received is the important thing, so the efficiency (fraction of transmitted power that is received) is the more significant parameter. For this reason, wireless power technologies are more limited by distance than wireless communication technologies.
HISTORY
In 1826 André-Marie Ampère developed Ampère's circuital law showing that electric current produces a magnetic field. Michael Faraday developed induction in 1831, describing the electromagnetic force induced in a conductor by a time-varying magnetic flux
Tesla demonstrating wireless power transmission in a lecture at Columbia College, New York, in 1891. The two metal sheets are connected to his Tesla coil oscillator, which applies a high radio frequency oscillating voltage. The oscillating electric field between the sheets ionizes the low pressure gas in the two long Geissler tubes he is holding, causing them to glow by fluorescence, similar to neon.
Hardware Specifications
• HF-Transformer
• Two air filled inductor coils
• Rectifier
• Transistors
• HF-diodes
• BLDC fan
• Voltage regulator
APPLICATIONS OF WIRELESS POWER TRANSFER
Several applications of wireless power transfer are apparent and obvious. Firstly, WPT could eliminate traditional charging systems in place today. Instead of plugging in a mobile phone or laptop via power cord to charge the battery, wireless power can be harnessed and implemented in a home such that a laptop and phone charge continuously and wirelessly without the need for plugging anything in. Higher level applications include charging of electric vehicles(EVs). As EVs become more and more prevalent on the roads, the feasibility of driving such a vehicle can be
maximized via stationary, and even mobile, WPT systems. Applications of WPT are described in this section.
3.1 Electronic portable devices
Cell phones, laptops, tablets, even smart watches are found all over the globe and are owned and used by billions of people. What these devices all have in common is the need to recharge their internal battery so that the device can be used while mobile. Such is the paradox of portable devices: they provide convenience by running off internal power so they can be used anywhere, but always must return to be tethered to a power cord in order to charge.
3.2 Electric Vehicles
As concern over global warming and greenhouse gas emissions grows across the globe, the prevalence of electric vehicles has also increased. One of the drawbacks of electric vehicles is their battery. Electric vehicles currently need to be plugged in to recharge their internal batteries, and take many hours to do so. However, many envision that in the near future, one need only park her car in a pre-determined spot in her driveway and the car will charge wirelessly and automatically.
3.3 Railways
The application of wireless power transfer technology to future transport system expands to railways by removing overhead power lines and pantograph of train system, we can reduce construction and maintenance cost and can increase the train speed. The biggest difference from the electric vehicle is the required power for the operation of the train. Fortunately, the train is always positioned just on the rail with minimal movement vertically and horizontally. Therefore, the air gap can be reduced to 8 cm, and the induced voltage is increased to 186% the WPT system with 20 cm.
3.4 Theoretical applications: Aerial Vehicles and Solar Power Satellites
While portable device and vehicle charging are applications that could be implemented in the near future, some other theoretical applications have been posited for further research and development. One such application is the Stationary High Altitude Relay Platform. The SHARP system consists of an unmanned airplane that flies at an altitude of approximately 13 miles above the earth, constantly circling the earth in a 2 kilometre diameter. The SHARP airplane would then be used as a communications relay. Here, the SHARP airplane has a large rectenna behind the wings, allowing for power to be transmitted to it from the earth, and thus is able to stay in the air for long periods of time, potentially months.
CONCLUSION
The goal of this project was to design and implement a wireless power transfer system via magnetic resonant
coupling. After analysing the whole system systematically for optimization, a system was designed and implemented.
Experimental results showed that significant improvements in terms of power-transfer efficiency have been achieved.
Measured results are in good agreement with the theoretical models. We have described and demonstrated that magnetic resonant coupling can be used to deliver power wirelessly from a source coil to a with a load coil with an intermediate coil placed between the source and load coil and with capacitors at the coil terminals providing a sample means to match resonant frequencies for the coils. This mechanism is a potentially robust means for delivering wireless power to a receiver from a source coil.