For the purposes of improving the restraint ability linked to electromagnetic energy in the space as well as the coupling efficiency, it is proposed that a magnetic coupler with a composite magnetic field would be required. This comes in the light of the wireless power devices, or the wireless power transfer which is a system said to make use of the high frequency electromagnetic field for the purposes of transmitting energy across the space. Researchers and designers have cited the convenience and safety of the system which may not need the use of bolts and cables. This may not be enough as developers look for better means of enhancing the coupling coefficient of the known WPT systems. One of such means is to consider the ferrite cores, which can be added to the magnetic coupler while making an attempt of optimizing the changing shape of the ferrite cores, a consideration that could benefit from engineering dissertation help. Based on this, the discussion will focus on how high Q factors can be achieved before focusing on the light weight shielding solutions. The others parts of this assignment will also focus on the light weight shielding solutions and simulation and design.
Quality factor is regarded as a significant property of the nano and micro electromechanical resonators, which are known for underlying the frequency sources, the timing references, the mass sensors, gyroscopes and the atomic force microscopes. A number of methods have been improvised for the purposes of tuning the effective quality factor of the said NEM and MEM resonators. Some of the approaches that would be highlighted in this context include the parametric pumping, mechanical pumping, the proportional feedback control and the thermal piezoresistive pumping. The mechanical Q factor is regarded as the most significant factor and it is largely regarded as a measure of the significant energy decay rate for every cycle of the vibrations (Miller et al. 2018). When the Q factor of the resonator is higher, then it implies that the coherent energy will essentially remain in the prior mode for a longer time before leaking to the environment. It is also worth noting that the Q factor is associated to thermo mechanical displacement of noise.
While focusing on engineering the significant underlying dissipation in the NEM and MEM resonator, it is also relevant to feed energy either in or out of the considerable mode for the purposes of either decreasing or increasing the decay rates. This means that it is important to modify the dynamics of the resonators without tampering with the fluctuations that tap into the actual dissipation. In the first approach of the proportional feedback, the resonator motion is initially transduced into what is referred to as an electrical signal before it can be filtered and thereafter phase shifted, and finally applied back to the force linked to the device (Hamidkhani et al. 2019). The thermo mechanical fluctuations attached to the flexural mode would essentially create an almost tiny current that emanate from sense electrode. This can subsequently be amplified into voltage and further filtered for the purposes of suppressing noise at significant frequencies that are away from the relevant resonance. The phase shifter as well as the tunable gain would be of use in amplifying the filtered signal (Miller et al. 2018). The significant component of the controller design covers the resonator stability in which the Laplace domain can be used in modelling the dynamics.
Same attention is given to the external velocity feedback control which triggers the enhancement mechanism applied across the commercial MEM oscillators, the NEM oscillators, the piezoelectric oscillators and the quartz crystal oscillators. Apart from the feedback control, attention is also given to optical pumping which attains the effective Q factor by simply coupling what is referred to as the mechanical resonator to the significant microwave or optical cavity. The coupling which happens between the mechanical and the optical degrees of freedom has a tendency of rising from the electron-hole generation, radiation pressure and the bolometric forcing (Miller et al. 2018). Essentially, coupling can be attained through engineering the resonator as well as the cavity for the purposes of allowing the displacement of the significant mechanical mode chances. This is possible in the course of modulating resonant frequency.
The air core wireless power devices are characterized majorly by the electromagnetic waves, which are generated by the electric field at the time when it interacts with the magnetic field. The produced oscillations of the magnetic field and the electric field are always perpendicular to one another, as well as perpendicular to the significant direction of the electromagnetic wave propagation. The waves would travel at a constant speed of approximately 3.0 x 108 m/s when it is vacuum. This is different from the mechanical waves which would need a medium for propagation. However, the air core wireless power devices are likely to suffer from electromagnetic interference, which is regarded as a disturbance that is commonly generated from the external radiation or conduction that would end up affecting the electrical circuit under consideration. These interferences are imminently encountered on a daily basis following the increased use of the wireless devices such as near-field communication, Wi-Fi, Bluetooth and even GPS among others (Zhang et al. 2018). Due to this, there is increased attention towards the EMI shielding materials which can be used in preventing the EM waves from making their way in an electric system either through absorption or reflection as part of the incident radiation power. Further attention is directed to the light weight shielding solutions. Some of the solutions provided include the use of foams, polymer based composite and aerogels, which are significant for the EMI shielding.
The first solution lies with the polymer-based composites, which preserves the advantageous lightness, design flexibility, low cost and the ease of processing. The polymer-based composites can contain the metallic fillers in which metals are regarded as typical wave reflection materials applied for the EMI shielding reasons given the abundance of the mobile charge carriers which can easily interact with the instantaneous EM radiations. The filters that take the physical forms like nano particles and fibres could be dispersed across the polymer matrix for the purposes of enhancing the interaction with radiations. However, challenges of attaining a better dispersion of the metallic fillers as well as the weight increase are likely to make the metallic fillers composites less convenient and less popular (Zhang et al. 2018). This has subsequently compelled an almost instantaneous switch to the intrinsically conducive polymers such as polypyrrole, polyaniline and polyacetylene.
Apart from the metallic fillers, another version of the composites includes the intrinsically conductive polymers, which constitute interplay of the desirable mechanical properties needed for support as well as electrically conducting component. The conducting polymers would constantly be referred to as the conjugated polymers in which there as an aspect of doping. Further alteration of the parameters like the dopant type, the chain size and even the synthesis route would subsequently have an impact on the molecular structure as well as the EMI shielding properties. Across the conducting polymers, the common types include the polyaniline (PANI) and the polypyrrole (PPY). The latter is known for a better stability, easy synthesis, less toxicological problem as well as high conductivity (Zhang et al. 2018). The electrochemical and the chemical polymerization of polypyrrole on the significant polyethylene terephthalate fabric have been cited as an example for the conducting polymer. PANI has been studied along the chemical and physical properties and the doping mechanisms. Other solutions provided along the composites include the carbon-based fillers in which the carbon pigments can be formed during the thermal decomposition of the hydrocarbons (Haerinia and Afjei 2016). Carbon fillers known for having high aspect ratio can be more effective in terms of imparting the electrical conductivities across the polymer matrix.
Apart from the composites, attention is shifted to the use of aerogels and foams for EMI shielding. The first type of foams include the polymer based composite foams, which are known for providing weight reductions as the pores give room for a decrease in terms of permittivity as reflected in the material surface. The electrically conducive filters such as the graphene sheets, the CNTs and CNFs can be applied as part of the desirable conducting network noted in the polymer foam matrix. Typical foam includes the syntactic foams, which enhances the commonly known EMI SE and the functionalization of HCMs as established in the epoxy syntactic foam (Haerinia et al. 2016). It is worth noting that the PDA coating would substantially support dispersion while playing the role of a reducing agent before making a deposit of the silver particles.
Other types of foams include the carbon foams which is regarded as a class of 3D architecture, which constitutes the interconnected network of carbon which is porous as well as sponge-like. The application of carbon foams in the EMI shielding constitute the excellent properties attached to them such as high resistance to temperatures, low density, electrical and thermal conductivity and resistance to chemical corrosions (Zhang et al. 2018). The graphene foams are also part of the wide range of foams that can be prepared with the help of stringent processing conditions.
The graphene aerogels come last and they appear in form of a synthetic porous material that is ultralight. The liquid component is substantially replaced by air. The application of the aerogels has recently been confirmed by researchers as far as EMI shielding is put into consideration. The significant conductive network has the capacity of retaining the advantageous light carbon textile.
The Finite Element, denote as FE simulation, is essentially a method that has been improvised in various physical problems in which governing differential equations can be attained. The guiding principle of FE lies behind the mathematical model. The FE simulation essentially studies the electromagnetic results associated to the aligned as well as the misaligned transceivers. The 2D COMSOL software is largely deployed in simulating a number of possible configurations. On the other hand, the CST studio suite gives developers an access to a range of the EM simulation solvers with such methods like the finite integration technique, the transmission line matrix and the finite element method. Most of these solvers are largely dedicated to both the static as well as low frequency application like sensors, transformers and other electromechanical devices.
The context focuses on attaining the coupling efficiency in the wireless power transfer (WPT). The consideration of FEM software solvers focuses on how the lightweight materials or the ferromagnetic materials are likely to affect the design the WPT system.
The power transfer efficiency would be evaluated against frequency for the coils while drawing comparisons with the ferrite or air cores following an operating frequency of 13.56MHz. The system is fabricated in the 0.35µm CMOS process, received power is 102mW and the receiver efficiency is 92.6%. The compensation capacitors can remain in place as the resonant frequency can be changed. However, the WPT system remains more susceptible to most of the ferromagnetic materials, which calls for readjustment of the capacitors (Tan et al. 2019). An increase in terms of ferrite cores is largely meant to boost the performance of the system as depicted in the graph below.
Apparently, the leakage magnetic flux is likely to reduce following an increase in terms of the magnetic coupling. However, the cheapest means of reducing the leakages is through the significant use of the metallic places with the Rx and Tx coils. This means that eddy currents emanating from the plates yields a magnetic field that can oppose the flux from the WPT coils. However, the metallic shielding plates have a tendency of altering the system parameters and even performance at the same time. According to FE simulation, the following performance is evident.
The simulation results indicate that given a system. Then it would be observed that when two shielding loops are at the same level, it follows that EMFs for the X and Z axes is likely to reduce.
With a constant operating frequency of 13.56 MHz, it is observable that resonant-reactive current shield would succeed at reducing to about 95% and 81% of the total EMF average especially for the x and z axis. When the Al-shield is introduced, then it would reduce to around 64% and 71% for x and z axis of the total EMF average. It is worth noting that the values could be compared to the significant ferrite shielding method.
While observing the inductances and the coupling coefficient, it is evident that a resonant-reactive current shielding would probably have high system performance. In the course of designing the WPT, weight is consistently treated as a significant factor
While striking the comparisons, it could be established that the ferrite shield is likely to be of good performance and it is still of lightweight. The major drawback for this shield is the high EMF leakages. However, the advantage provided by the ferrite shield may not be far from the mentioned intrinsically conductive composites and the metallic fillers which are of light weight and exhibit electrical conductivity. While the conductive composite is more preferable compared to the metallic fillers, the former still takes the doping advantage which initiates the property of electrical conductivity. With the help of FE simulation, the preferable properties could rarely be observed in the Aluminium shield which is of heavy weight as well as bad system performance. The resonant reactive current equally exhibits a better system performance and it is of lightweight when compared to the mentioned aluminium shield. Amid the design, developers need to pay attention to two key components of the system (Karimi et al. 2016). The shielding loop position has been investigated and observed that when the given loop is placed at the same level with WPT coils, the EMF would go down for power devices. It is important to note that shielding impedance need to be controlled for the purposes of achieving a better frequency.
A critical focus on health and safety effects takes note of the essence of the materials applied in EMI shielding. The materials are increasingly required in the protection of the electronic devices from the interference problems while trying to avoid the dangerous effects on the human health as far as electromagnetic radiation is concerned. For instance, EMI shielding of the metalized PPY coated woven as well as the non-woven fabrics can be facilitated in a frequency range of around 100-1000 MHz. From this, one can determine the insertion loss data, which equally reflects on the shielding effectiveness, absorption and reflection coefficients. Briefly, electrical currents are believed to exist naturally in the human body and would be regarded as a significant part of the normal body functions.
However, effects of the external exposure to the EMF especially on the human body cells largely depends on the frequency and magnitude of EMF. Due to this exposure, ELF magnetic fields could be classified as carcinogenic to human beings as noticed in the studies of the known childhood leukaemia. Therefore, there is need to reduce exposure of humans to the EMF fields and this can be achieved in different ways with the help of the light EMI shielding solutions. First, the light EMI shielding solutions provide the shielding efficiency in the sense of absorption and reflection. When EM waves touch on the front face of any material, then part of the incident power is likely to be reflected and the rest if absorbed as well as dissipated in the significant from of energy. Other parts of this energy are transmitted through the material.
P, H and E denote and the power as well as the magnetic and electric field intensities and the subscripts R, T and I denoted the reflected, transmitted and the incident components. First, the reflection is regarded as the primary function of lightweight EMI shielding. For the purposes of safety, the materials need to have the mobile charge carriers for them to reflect the EM radiation. The absorption loss is regarded as the secondary function of the EMI shielding. In this case, the material is characterized by the attenuation constant and thickness. The attenuation constant essentially defines extent to which the intensity of the wave can be reduced when passing through the material. Shielding, for the purposes of achieving safety, is dominated by absorption compared to reflection.
The discussion aimed at establishing the FE simulation for the light weight EMI solutions. Early observations noted in the discussion include attaining the coupling efficiency under the magnetic coupler that exhibits the composite magnetic field. Therefore, developers have been keen on means of enhancing the coupling efficiency in the WPT. Addition of the ferrite cores has been regarded as the cheapest way as far as the light weight shielding solutions are put into consideration. The discussion further looked at ways of enhancing the quality factor. A number of methods have been recommended to achieve high Q factor, which include mechanical pumping, proportional feedback control and parametric pumping among others. More attention was paid to light weight shielding solutions which have been discussed in a number of ways including the composites, foals and aerogels. Finally, there was need to consider a simulation of a WPT system while considering the coupling coefficient with the help of the ferrite cores.
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Haerinia, M. and Afjei, E.S., 2016, June. Investigation of receiving pot core effect on magnetic flux density in inductive coupling-based wireless power transfer. In 2016 International Symposium on Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM) (pp. 541-545). IEEE.
Haerinia, M., Mosallanejad, A. and Afjei, S.E., 2016. Electromagnetic analysis of different geometry of transmitting coils for wireless power transmission applications. Progress In Electromagnetics Research, 50, pp.161-168.
Hamidkhani, M., Sadeghi, R. and Karimi, M., 2019. Dual-Band High Q-Factor Complementary Split-Ring Resonators Using Substrate Integrated Waveguide Method and Their Applications. Journal of Electrical and Computer Engineering, 2019.
Karimi, P., Ostoja-Starzewski, M. and Jasiuk, I., 2016. Experimental and computational study of shielding effectiveness of polycarbonate carbon nanocomposites. Journal of Applied Physics, 120(14), p.145103.
Miller, J.M.L., Ansari, A., Heinz, D.B., Chen, Y., Flader, I.B., Shin, D.D., Villanueva, L.G. and Kenny, T.W., 2018. Effective quality factor tuning mechanisms in micromechanical resonators. Applied Physics Reviews, 5(4), p.041307.
Tan, L., Elnail, K.E.I., Ju, M. and Huang, X., 2019. Comparative Analysis and Design of the Shielding Techniques in WPT Systems for Charging EVs. Energies, 12(11), p.2115.
Zhang, L., Bi, S. and Liu, M., 2018. Lightweight Electromagnetic Interference Shielding Materials and Their Mechanisms. In Electromagnetic Materials. IntechOpen.
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