Analysis of Various Inductor Core Materials for Wireless Power Transfer

Transcription

1 Middle-East Journal of Scientific Research 24 (4): , 2016 ISSN IDOSI Publications, 2016 DOI: /idosi.mejsr Analysis of Various Inductor Core Materials for Wireless Power Transfer T. Rampradesh, R. Vignesh and A. Nivedha Department of Electrical & Electronics Engineering, IFET College of Engineering, Tamil Nadu, India Abstract: Wireless power transfer can make an extraordinary change in the field of electrical engineering, which eliminates the use of conventional copper cables and current carrying wires. Here we introduce the basic concepts of wireless power transfer using electromagnetic induction and compare the performance in terms of temperature and electric field intensity of inductors with three different types of core materials such as air core, ferrite core and iron core. The model was simulated using Ansys and Pro-e environment and a comparative analysis is made using bar charts. Its future applications includecharging of mobiles, electrical vehicles, sensing smoke, detecting gas, etc. It can also be used for certain remote applications. Key words: Electrical energy Energy transfer Receiving stations Electric load Magnetic resonance INTRODUCTION upon the number of turns and the material used for the core and the coil [1]. These parameters decide the The transfer of electrical energy from a power source temperature and the electric field intensity of the inductor to an electric load without a direct physical connection which has a direct impact on the efficiency of the between them, usually via an electromagnetic field, is inductor. defined as Wireless Power Transfer Technology (WPTT). Nowadays electronic devices such as cell phones and Concept of WPT Technology: The general concept of laptops need WPTT for wireless charging with the WPT (Wireless power) [2, 3] is based upon the advantage of protection from any faults at external power principle of electromagnetic induction. The model source. consists of a transmitter coil and a receiver coil. In the 1890 s, a Wireless Power Transfer (WPT) The coils are inductors that are placed a suitable system was demonstrated by Nikola Tesla using resonant distance. The transmitter coil is powered by a transformers called Tesla coils. In July 2007, a group of generator or any power source as shown in Fig. 1. The researchers at MIT presented a method of transmitting power in the transmitter coil is electromagnetically power wirelessly. The researchers used an coupled with the receiver coil which is placed at a electromagnetically coupled resonance system to power suitable distance [4]. Thus the receiver coil is energized a 60W bulb wirelessly from a distance over two meters and wireless power transmission is achieved. ater the away. The magnetic resonance coupling technology has power is rectified and regulated according to the load been found to be viable for midrange energy transfer. It is conditions. used for charging the electric vehicles with energy efficiency up to 90% in a relatively short time. It is also Transmitter and Receiver Side: Transmitter and receiver used for low power wireless charging of mobile phones coils are inductor coils which are used to transfer the with a power up to five watts and energy efficiency up to power over a specified distance. The power transfer is 70%. done by the means of mutual induction [5, 6]. The The main research theme of all WPT technology is magnetic coupling is specified for some fixed distance. looking for improving the transmission efficiency and the This distance depends upon magnetic field of the coil distance between the transmitter and the receiving received by an air core receiver coil. Greater the magnetic stations. The inductor is usually a coil wrapped around a field, greater the distance over which the power is core material. The efficiency of the inductor depends transferred. Corresponding Author: T. Rampradesh, Department of Electrical & Electronics Engineering, IFET College of Engineering, Tamil Nadu, India. 1283

2 Fig. 1: Concept of WPT Core Material Properties: Air core inductor is the type where no solid core exists inside the coils. In addition, the coils that wound on nonmagnetic materials such as ceramic and plastic are also considered as air cored. Calculation of the inductance to design air core inductor: 2 2 = (d * n )/ (18d+40 l) (1) where, is inductance in micro Henrys, d is coil diameter in inches, l is coil length in inches and n is number of turns. Fig. 2: Transmitter side Iron Core Inductor: The inductance value on the air core inductor depends on the number of spires (turns), length, diameter, thickness of the spiral, etc. The air core inductance range values are limited. In order to increase the inductance value of an inductor, an iron core is placed inside of it. This iron core has very special magnetic characteristics. What they do is to reinforce the magnetic field. The magnetism of the core material depends on the bias of the molecular magnetic domains, when the magnetic field that affects the inductor changes in a continuous way. These domains should be able to change its position so that the core meets its goal. The magnetic domains may or may not follow the magnetic field variations depending Fig. 3: Receiver side on the material the core is made of. If the magnetic field variation cannot be followed, the core is useless and the The high frequency alternating current, which is molecular domains get disordered, leaving the core linked with the wireless power transmitting coil (Fig. 2), magnetically unbiased. would create an alternating magnetic field in the coil due to induction, to transmit energy. In the wireless power Calculation of inductance to design iron core receiver section, the receiver coils (Fig. 3) receives that inductor: energy as an induced alternating voltage (due to induction) in its coil [7, 8]. 2 = A *N (2) 1284

3 where, N is a number of turns A is inductance factor Ferrite Core Inductor: Ferrites are one of the main core materials used in inductors and transformers. Ferrite inductor is used to provide an increase in the permeability of the medium around the coil to increase the inductance of the inductor. Ferrites are widely used within inductor technology to improve the performance of the inductor. Ferrites are basically iron based magnetic material in the form of a ceramic. Ferrites are made from a powder and can therefore be manufactured in a variety of shapes according to the requirements. The inductor was designed with three different types of core materials viz., air core, iron core and ferrite core. All three inductors had a copper coil of 12 turns per coil. The three inductors with different core materials were simulated separately and the values of electric field intensity and temperature for the three cases were compared. The output results are shown in Fig. 4 to 9. 2 (nh) = A *N, (3) where, is the inductance in nano henries, N is the number of turns of wire in the coil wound around the ferrite rod (centered on the rod), A is the inductance factor which describes the rods ability to provide inductance. The A values are in units of (nh/turn squared) which are the same as A values in units of (mh/1000 turns). The inductance factor (A ) is not a constant; it depends on the length of the coil. As the coil length decreases, the value of A increases. Fig. 4: Air core Electric Field Intensity A values Number of turns = Or desiredinductance (mh) (1000) (mh/1000turns) A value (4) Numberof turns = desiredinductance(uh) (100)A (uhy/100turns) A value (5) A value = (in uh) No.of.turns (uh/100turns) (6) 1000 A (uh/1000 turns) = (in uh) (7) Noof turns Simulation Result: The performance characteristics of inductors, in terms of temperature and electric field intensity are analyzed in Ansys and Pro-e environment. ANSYS is a general purpose software, used to simulate interactions of all disciplines of physics, structural, vibration, fluid dynamics, heat transfer and electromagnetic for engineers.pro-eknown as Pro/ENGINEER is a parametric, integrated 3D CAD/CAM/CAE solution created by Parametric Technology Corporation (PTC). 2 Fig. 5: Ferrite core Electric Field Intensity Table 1: Simulation result of different type of core material Core Material Magnetic Field Intensity (V/m) Temperature (w/m ) Air Core Ferrite Core Iron Core From Table 1 and Fig. 10 and 11 ferrite core has high magnetic field intensity and less temperature rise. To improve the efficiency and distance between the coils in wireless power transfer, ferrite is the best core material to design an inductor based on the above simulation results. 1285

4 Fig. 6: Iron core Electric Field Intensity Fig. 7: Air core Joule Heat Fig. 8: Ferrite core Joule Heat 1286

5 Fig. 9: Iron core Joule Heat Fig. 10: Magnetic field intensity for different core materials Fig. 11: Temperature for different core materials 1287

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