Student Conference zyxwvutsr on Research and Development zyxwvut (SCOReD) 2003 Proceedings, Putrajaya, Malaysia CableIess Battery Charger Using Induction Technique for Electric Vehicles Nasrul Humaimi Mahmood, Mohamed Amin Alias, Mohd Wazir Mustapha, Mazlina Esa and Faridah Taha Cordless Charger Research Group Faculty of Electrical Engineering, Universiti Teknotogi Malaysia 81300 UTM Skudai, Johor, Malaysia e-mail: nasriil~)suria.nie.ulm.my Abstract- Electromagnetic induction is the production of an electromotive force in zyxwvutsr a conductor as a result of a changing magnetic field about the conductor. The induced emfalways such that it opposes the change that gives rise to it, according to Lenz’s law. In our work, we are considering in controlling the magnetic flux distribution through zyxwvuts an air-gap during the energy transfer from the source to load. This research has put a core situation in investigating the possible ways of charging the batteries via mutual induction as in transformers. This enables the charging process to he cableless. It involves two coils transferring energy from one to the other through air in the most cffrcient way. Our work is presented in this paper. Simulation and hardware implementation has been carried out successfully. We have measured the magnetic flux density for ac input voltage of 100 Volt with different frequency values. The optimum frequency in our design is 25 Hz. We found that it is possible to control the magnetic flux distribution during energy transmission by optimizing the frequency and shielding the flux path. Keywords Cordless charger, induction, magnetic flux control. I. INTRODUCTION The work described in this report is an altemative charging of the battery for electric vehicles. In our work, we introduce the charging method to be cableless since without connector, we can safe our time of plugging the connector and this will be more efficient. We can build a parking lot with the primary coil embedded in a parking lot, which provide magnetic field as a medium of energy transfer to charge the electric vehicle’s battery. The secondary coil is mounted on electric vehicles and received the energy from primary coil via mutual inductance. This charging method is suitable for shopping complex’s car park and other places which require a big space of parking tots. The investigatian of charging the battery via mutual induction as in transformer is divided into software simulation and hardware implementation. We used Finite EIement Method Magnetic software (FEMM ver 3.1) for the simulation work while the experiments have been done in R&D Electronics laboratory at Faculty of Electrical Engineering, UTM. 0-7803-8 zyxwvutsr 173-4/03/$17.00 02003 IEEE, 207 11. SOFTWARE IMPLEMENTATION FEMM 3.1 software is very useful in modeling the magnetic flux distribution for different shape of core. We developed five optimum samples of the design with contour and density plots. One of the most useful ways to understand the magnetic finite element solution is by piottihg’ the “flux lines”. These are streamlines along which flux flows in the finite element geometry. When tlux lines are close together, the flux density is high. From the design, the primary and secondary cores are integrated to visualise the magnetic field energy for bath cores. The small difference in values indicates that the design is possible to transfer the energy with low losses. Figure 1 (a) to (e) explain the pattern of magnetic flux distributions for different designs of core shapes. From all the patterns, it can be seen that the shape of the core plays an important role in determining the magnetic flux lines distributions. For example, compare pattern 1 and pattern 2. If we make the ends of bath the primary arid secondary cores as concave surfaces, the magnetic flux lines converge from the end part of primary and secondary. As the magnetic flux lines decrease, this will give better results since we can reduce the losses. However, there are still a lot of joint flux lines between the end part of primary which can reduce the output voltage at secondary coils. To solve this, we need to increase the distance between the end parts of each core as shown in Figure l(c). As a result, we can see that the joint magnetic flux lines decreases and this will make sure that more magnetic flux from primary is induced into the secondary part. Figure l(d) and (e) are the effects of magnetic flux fines distribution as we decrease the size of the end part of the primary compared to the secondary end part. From the density plot (Tesla), we can see that more magnetic flux lines from the primary part enter the secondary part of the core and this shows us that by decreasing the primary shape, we can get better results compared to others. To make clear which is the best pattern that we are going to use later, we integrate the primary and secondary pait for each patterns and find the minimum losses during the , energy transnussion. The lowest percentage of losses will give better results of possible