Search

In this chapter, it is explained that not only the magnetically coupled inductors but also all inductive power transfer systems (IPTSs) inherently have the nature of a gyrator. Widely known characteristics of IPTSs such as impedance inversion and source‐type conversion are proved to be the nature of the gyrator. A graphical approach that utilizes the gyrator is explained for the modeling of IPTSs in general. The proposed graphical technique enables manipulations on the circuit diagram instead of on the circuit equations, which are difficult to handle when the system order is higher than 4. Hence, the equivalent model can be obtained almost by inspection conveniently, giving fruitful physical insights that are limitedly achieved with equation manipulations. Steady‐state analyses at any frequency are possible and equivalent series resistances can also be included in the proposed model. Five selected electrical characteristics, that is, source‐to‐load gain, load‐independent output voltage/current characteristics, power factor at the source, sign of the source phase angle, and allowances of open/short loads are evaluated for three widely used IPTS topologies. Also, this technique is extended to the mistuned case for verifying the general use of the approach. An experiment for the voltage‐source‐type inductor–capacitor–inductor secondary‐parallel (V‐LCL‐P) topology is demonstrated for the cases of both perfectly tuned and mistuned situations at 85 W and 100 kHz.This chapter is based on the paper by Y.H. Son, B.H. Choi, G.‐H. Cho, and Chun T. Rim, “Gyrator‐based analysis of resonant circuits in inductive power transfer systems,” IEEE Trans. on Power Electronics , vol. 31, no. 10, pp. 6824–6843, October 2016.

As discussed in the previous chapter, large tolerance is one of the best characteristics of a static electric vehicle (EV) charger, but only if no severe penalty for the larger tolerance is found. In this chapter, an explanation is given of asymmetric coil sets for wireless stationary EV chargers, which have a significantly larger lateral tolerance than any others in the world.The pick‐up coil set is much smaller than the power supply coil set, thereby allowing large lateral and longitudinal displacements as well as robustness to airgap displacement. EMF is reasonably reduced by arranging magnetic poles along the EV's moving direction so that alternating magnetic flux through adjacent poles cancel each other. A dominant field analysis (DoFA) useful for complex vector magnetic flux simulation is used, which was introduced in Chapter 15 and is applicable to any resonating coils of inductive power transfer systems (IPTSs). Furthermore, a hysteresis loss model is suggested, which appropriately reflects the partial core saturation in a system analysis.A prototype IPTS including the proposed coil sets were designed and successfully verified by experiments. In the quick charging mode, maximum output power of 15 kW, large lateral displacement of 40 cm, longitudinal displacement of 20 cm, and an airgap of 15 cm were achieved, and low EMF of 6.1 μT at 20 kHz was achieved in the normal charging mode of 5 kW.This chapter is written based on the paper by S.Y. Choi, B.W. Gu, J. Huh, W.Y. Lee, J.G. Cho, and C.T. Rim, “Asymmetric coil sets for wireless stationary EV chargers with large lateral tolerance by dominant field analysis,” IEEE Trans. on Power Electronics , vol. 29, no. 12, pp. 6406–6420, December 2014.

To minimize the greenhouse effect caused by emission of CO 2 , many automobile manufacturers are developing battery???powered automobiles that typically use rechargeable lithium ion batteries. However, the future of these battery electric vehicles (BEVs) is less than certain.The rechargeable lithium batteries are heavy and expensive with a limited life. As an alternative to this BEV, road???powered electric vehicles (RPEVs) have been developed, which utilize the dynamic charging technologies; one of the recently developed examples is the on???line electric vehicle (OLEV).OLEV draws its electric power from underground electric coils without using any mechanical contact. Batteries are recharged whenever OLEV draws electric power from the underground coils and thus does not require expensive separate charging stations. The infrastructure cost of installing and maintaining OLEV is less than those required for other versions of electric vehicles.Detail rationales for dynamic charging will be covered in succeeding chapters, but the overview will be provided in this chapter.

Very often the dynamics of AC circuits such as AC power converters, AC power circuits (filters, power lines, etc.), AC motors, and inductive power transfer (IPT) systems should be identified to design the main circuit and controller. In this chapter, phasor transformation theory applied to the static analysis of linear AC converters is extended to the dynamic analysis of linear AC converters. A complex Laplace transformation is adopted for the dynamic analysis of phasor transformed AC converters. It is rigorously verified by mathematics and simulations that any linear AC converter dynamics can be completely explored by the proposed complex Laplace transformation together with the conventional phasor transformation. This ???unified general dynamic phasor??? is a good analytical tool for IPT dynamics study.This chapter is based on the paper by C.B. Park, S.W. Lee, and C.T. Rim, ???Static and dynamic analyses of three???phase rectifier with LC input filter by Laplace phasor transformation,??? in IEEE ECCE 2012 , September 2012, pp. 1570???1577.

As an extended work of a previous chapter, a dipole‐coil‐based extremely loosely coupled inductive power transfer system (IPTS) for wireless sensors over a wide range is explained in this chapter. The overall superiority of dipole coils for a long‐distance power delivery over loop coils with an identical configuration of a square core is verified by comparing the magnetizing inductance between primary and secondary coils. Series–parallel resonant circuits were used to achieve a higher load voltage than that of the series–series scheme. Contrary to conventional IPTSs or coupled magnetic resonance systems, the quality factor Q was set as low as 100, guaranteeing a frequency tolerance of 1%, where a prototype of narrow dipole coils with a length of 2 m was used to deliver 10.3 W of power up to 7 m away at a low frequency of 20 kHz. The powering capabilities of the proposed IPTS were experimentally compared inside and outside of a metal container 8 m × 4 m × 2.5 m in size at different frequencies ranging from 20 kHz to 150 kHz, where the proposed IPTS is highly likely to be surrounded by arbitrary distributed conductors in most wireless sensor usage environments. The coupling coefficient κ between the primary and secondary coils was measured over a long distance from 2 m to 12 m for different secondary coil positions, where κ is mostly much less than 0.01. A comparative analysis of the maximum amounts of load power among different core materials, that is, two ferrite cores and an amorphous core, was conducted in relation to the design of a secondary coil. The results were verified by experiments at a given switching frequency of 20 kHz.This chapter is based on the paper by B.H. Choi, E.S. Lee, J.H. Kim, S.J. Yoo, and C.T. Rim, “Dipole‐coil‐based wide‐range inductive power transfer systems for wireless ensors,” IEEE Trans. on Industrial Electronics , vol. 6, no. 5, pp. 3158–3167, May 2016.

The 5 m off‐distance inductive power transfer systems that have optimally shaped cores in the primary and secondary coils are explained. Instead of conventional loop‐type coils for a magnetic resonance scheme, magnetic dipole‐type coils with cores are used for a drastic reduction in deployment space and quite long wireless power transfer. An optimized stepped core structure is also proposed, where a strong magnetic field section is so thick that magnetic field density may be even. Thus, the proposed optimized stepped core has only a 41% core loss compared with an unoptimized even core but delivers 2.1 times more wireless power for a given amount of core. Experimentally obtained maximum output powers and primary‐coil‐to‐load‐power efficiencies for 3 m, 4 m, and 5 m at 20 kHz were 1403 W, 471 W, and 209 W and 29%, 16%, and 8%, respectively. This chapter is based on two papers by The 5 m off‐distance inductive power transfer systems that have optimally shaped cores in the primary and secondary coils are explained. Instead of conventional loop‐type coils for a magnetic resonance scheme, magnetic dipole‐type coils with cores are used for a drastic reduction in deployment space and quite long wireless power transfer. An optimized stepped core structure is also proposed, where a strong magnetic field section is so thick that magnetic field density may be even. Thus, the proposed optimized stepped core has only a 41% core loss compared with an unoptimized even core but delivers 2.1 times more wireless power for a given amount of core. Experimentally obtained maximum output powers and primary‐coil‐to‐load‐power efficiencies for 3 m, 4 m, and 5 m at 20 kHz were 1403 W, 471 W, and 209 W and 29%, 16%, and 8%, respectively.This chapter is based on two papers, one by C.B. Park, S.W. Lee, and C.T. Rim, “5 m‐off‐long‐distance inductive power transfer system using optimum shaped dipole coils,” ECCE‐ASIA , June 2012, pp. 1137–1142 and the other by C. Park, S. Lee, G.H. Cho, and C.T. Rim, “Innovative 5m‐off‐distance inductive power transfer systems with optimum shaped dipole coils,” IEEE Trans. on Power Electronics , vol. 30, no. 2, pp. 817–827, February 2015.

In this chapter, the well???known coupled magnetic resonance system (CMRS) is explained, stating that it is nothing but new and is a sort of conventional inductive power transfer system (IPTS). There are three major magnetic couplings between coils in CMRS: source???transmitter (Tx), Tx???receiver (Rx), and Rx???load couplings, respectively. Except for Tx???Rx coupling, other couplings do not directly contribute to wireless power transfer. Hence, this miscellaneous coupling can be replaced with a lumped transformer with a ferrite core. Because there is only a Tx???Rx coupling, the CMRS becomes compact in size and robust to ambient changes. Moreover, the design of CMRS is drastically simplified without complicated multiresonance tunings due to a small magnetic flux linkage from the source coil or the load coil.Coreless coils are used for Tx and Rx coils to examine the characteristics of CMRS with lumped transformers. A detailed static analysis on the explicit circuit model of the proposed CMRS and design procedures are fully established. Experiments for 1 W and 10 W prototype CMRSs with a class???E inverter at the switching frequency of 500 kHz, where the quality factors are less than 100, verified the usefulness of the proposed model, achieving 80% of the maximum Tx coil???to???load efficiency. It is concluded that the conventional CMRS, in general, is just a special form of IPTS where the quality factor is extremely high with coreless Tx and Rx coils.This chapter is based on two papers, one by B.H. Choi, E.S. Lee, J. Huh, and C.T. Rim, ???Lumped impedance transformers for compact and robust coupled magnetic resonance systems,??? IEEE Trans. on Power Electronics , vol. 30, no. 11, pp. 6046???6056, November 2015 and the other by J. Huh, W.Y. Lee, S.Y. Choi, G.H. Cho, and C.T. Rim, ???Frequency???domain circuit model and analysis of coupled magnetic resonance systems,??? Journal of Power El ectronics , vol. 13, no. 2, pp. 275???286, March 2013.

In this chapter, the fundamental principles of wireless power transfer (WPT) are explained. As introduced in Figure 1.2 of Chapter 1, WPT includes inductive power transfer (IPT), capacitive power transfer (CPT), RF power transfer (RF PT), and optical power transfer (optical PT). Because RF PT and optical PT have been briefly introduced in Chapter 1, IPT and CPT will be mainly introduced in this chapter as WPT unless otherwise specified.

As an improved solution to the I‐type power supply rail, as explained in the previous chapter, a dq I‐type power supply rail is introduced in this chapter. The single‐phase I‐type power supply rail for on‐line electric vehicles (OLEVs) has a very narrow power supply rail with 10 cm width and exposes pedestrians to a very low electromagnetic field due to its alternatively arranged magnetic poles along the driving direction of electric vehicles; however, it has a major drawback: sinusoidal variation of the induced pick‐up voltage depending on pick‐up positions on the power supply rail along the driving direction. To overcome this disadvantage, a dq‐power supply rail fed by two high‐frequency AC currents of the d‐phase and q‐phase is introduced in this chapter. The d‐phase and q‐phase magnetic poles are alternatively arranged in a line; hence, the induced voltage of a pick‐up becomes spatially uniform. The power invariant characteristic of the proposed scheme has been verified by analysis, simulations, and experiments. A practical winding method is suggested as well.This chapter is based on the paper by C. Park, S. Lee, S.‐Y. Jeong, G.H. Cho, and C.T. Rim, “Uniform power I‐type inductive power transfer system with DQ‐power supply rails for on‐line electric vehicles,” IEEE Trans. on Power Electronics , vol. 30, no. 11, pp. 6446–6455, November 2015. Readers should gain much insight from the dq‐power supply rail.

Different from previous chapters of inductive power transfer (IPT), this chapter introduces capacitive power transfer (CPT) for static wireless electric vehicle (EV) chargers. A four‐plate compact capacitive coupler and its circuit model for a large airgap distance CPT is proposed. The four plates are arranged vertically, instead of horizontally, to save space in EV charging applications. The two plates that are on the same side are placed close to each other to maintain a large coupling capacitance and are of different sizes to maintain the coupling between the primary and secondary sides. The circuit model of the coupler is presented, considering all six coupling capacitors. The LCL compensation topology is used to resonate with the coupler and provide high voltage on the plate to transfer high power. The circuit model of the coupler is simplified to design the parameters of the compensation circuit. Finite element analysis (FEM) is employed to simulate the coupling capacitance and design the dimensions of the coupler. The circuit performance is simulated in LTspice to design the specific parameter values. A prototype of a CPT system was designed and constructed with the proposed vertical plate structure. The prototype achieved an efficiency of 85.9% at 1.88 kW output power with a 150mm air gap distance.This chapter is based on the recently published paper by Chris Mi (H. Zhang, F. Lu, H. Hofmann, W. Liu, and C. Mi, “A 4‐plate compact capacitive coupler and LCL compensation topology for capacitive power transfer in electric vehicle charging applications,” IEEE Trans. on Power Electronics , vol. 31, no. 12, pp. 8541–8551, December 2016). Those who want to investigate further can read another CPT paper by him (F. Lu, H. Zhang, H. Hofmann, and C. Mi, “An inductive and capacitive combined wireless power transfer system with LC‐compensated topology for electric vehicle charging application,” IEEE Trans. on Power Electronics , vol. 31, no. 12, pp. 8471–8482, December 2016).

In this chapter, an advanced version of on‐line electric vehicles (OLEVs) is introduced as an introductory example of road‐powered electric vehicles (RPEVs). Because the author is heavily involved in the development of OLEVs, this chapter will guide readers to how practical problems are dealt with. This chapter is based on the paper by J. Huh, S.W. Lee, W.Y. Lee, G.H. Cho, and C.T. Rim, “Narrow‐width inductive power transfer system for on‐line electrical vehicles,” IEEE Trans. on Power Electronics , vol. 26, no. 12, pp. 3666–3679, December 2011.The inductive power transfer system (IPTS) with a narrow rail width, a small pick‐up size, and a large airgap is explained, as an extension of previous research on OLEVs, in this chapter. By introducing a new core structure, the orientation of the magnetic flux alternates along with the road; hence, an inductive power transfer system with a narrow rail width of 10 cm, a large airgap of 20 cm, and a large lateral displacement of about 24 cm was implemented. The resonant circuit of the inductive power transfer system, driven by a current source, was fully characterized. The experimental results showed that the maximum output power was 35 kW and that the maximum efficiency was 74% at 27 kW.

Increasing use of wireless power transfer (WPT) in electric vehicles (EVs) is stationary charging, referred to as static charging in this chapter. This is because of the large number of passenger cars that are ready to be used by many potential customers. Automatic refueling of a vehicle is a wonderful thing for the person bored with repeated daily cable charging of EVs.As identified from recently developed autonomous vehicles and self‐controlled vehicles, future vehicles will be not only transportation tools but also information platforms. EVs are inherently the most electrified vehicles, which makes the information platform possible. Recently, the number of EV purchasers in the world have been increasing by more than 50% annually, despite the very low petroleum price. This means that EVs are not preferred just because of low operating costs.In this chapter, the need and general features of static chargers are discussed and coil design and standardization issues are explained in detail. The chapter is based on the tutorial material of mine at the 2016 IEEE ECCE‐Asia and the tutorial material of Chris Mi.

In this chapter, a general overview of electric vehicles (EVs) is briefly provided because EV is one of the major applications of WPT in this book. Currently, IPT is a majority method for EV charging though CPT is being researched as a potential candidate. Neither detail nor professional introduction to EVs will be tried in this chapter because this book is not intended for EV but for WPT. Those who are aware of EVs may skip this chapter.

As a further step to go forward to a more improved performance on the inductive power transfer system (IPTS) for road‐powered electric vehicles (RPEVs), an ultra‐slim S‐type power supply rail, which has a width of only 4 cm, is explained in this chapter. The cross‐section of the core has a thin S‐shape, and a vertical‐wound multiturn coil is displaced inside the core. Therefore, this design provides a very slim power supply rail, which is crucial for the commercialization of RPEVs. The construction of roadway infrastructure, which is responsible for more than 80% of the total deployment cost for RPEVs, can be much easier when the width of the power supply rail is so small. To increase portability and to minimize construction time, a foldable power supply module is also proposed in which flexible power cables connect each foldable power supply module such that no connectors are needed during deployment. An effective winding method for minimizing cable length is proposed, and an optimum core thickness of the proposed power supply rail is determined by FEA simulations and verified by a prototype power supply module. By virtue of the ultra‐slim shape, a large lateral displacement of 30 cm at an airgap of 20 cm was experimentally obtained, which is 6 cm larger than that of the I‐type power supply rail. In addition to the larger lateral displacement, it is estimated that the S‐type one has a lower EMF than the I‐type one because the width of the S‐type one is narrower than that of the I‐type one. The maximum efficiency, excluding the inverter, was 91% and the pick‐up power was 22 kW.This chapter is written from the paper by S.Y. Choi, B.W. Gu, S.Y. Jeong, G.C. Lim, and Chun T. Rim, “Ultra slim S‐type power supply rails for road powered electric vehicles,” IEEE Trans. on Power Electronics , vol. 30, no. 11, pp. 6456–6468, November 2015. Readers will be able to see not only how to make the power supply rail slim but also how important the modularity design is to carry and deploy.

In addition to the asymmetric coil structure in the previous chapter, another idea of increasing tolerance is to use DQ power supply coil sets for wireless stationary electric vehicle (EV) chargers. Two coil sets having a 90 phase difference can increase tolerances for longitudinal, lateral, as well as diagonal displacements. Each power supply coil set consists of two same magnetic poles to generate uniform magnetic flux density over the power supply coil. A prototype inductive power transfer system (IPTS) using the proposed DQ power supply coil sets for the wireless stationary EV chargers was fabricated for the experimental verifications with an operating frequency of 85 kHz to satisfy Standard J2954 of the Society of Automotive Engineers (SAE). From simulation and experiment results, it is found that the lateral, longitudinal, and diagonal displacements of the proposed coil sets increase by about 35% and 19%, respectively, at an airgap of 150 mm, compared with conventional rectangular loop‐type coils.This chapter is based on the paper by S,Y. Jeong et al. , “DQ‐quadrature coil sets with large tolerance for wireless stationary EV chargers,” in IEEE 2015 WoW , June 2015.

Improved magnetic mirror models (IM 3 ) for mono and dual coils with a finite width and infinite permeability are explained in this chapter [47]. By introducing a mirror current, which is located at the same distance from a source current but with a smaller magnitude than the source current, the magnetic flux density of the mono and dual coils can be determined in a closed form. The ratio of the mirror current and source current is identified as a function of the width of the core plate and the distance between the source current and core plate, as rigorously derived from the finite‐element method (FEM) simulations. Applying the proposed IM 3 to the mono and dual coils used for wireless electric vehicles, the magnetic flux density over an open core plate is analyzed and its maximum points on the plate are found, which is crucial in the design of the coils to avoid local magnetic saturation. Furthermore, the magnetic flux density when a pick‐up core plate is positioned over a primary core plate is also analyzed by introducing successive mirror currents. The proposed magnetic mirror models are extensively verified by experiments as well as site tests, showing quite promising practical usefulness.This chapter is based on the paper by W.Y. Lee, J. Huh, S.Y. Choi, X.V. Thai, J.H. Kim, E.A. Al‐Ammar, M.A. El‐Kady, and C.T. Rim, “Finite‐width magnetic mirror models of mono and dual coils for wireless electric vehicles,” IEEE Trans. on Power Electronics , vol. 28, no. 3, pp. 1413–1428, March 2013.

Due to strong and high‐frequency magnetic field between transmitting (Tx) and receiving (Rx) coils of wireless stationary electric vehicle (EV) chargers, there is the possibility of them catching fire from debris of a metal piece in the magnetic field, which is inductively heated during charging. Position detection (POD) of misalignment between Tx and Rx is also needed to deliver maximum power at the optimum position.In this chapter, the FOD and POD are explained, introducing dual‐purpose non‐overlapped coil sets for both FOD and POD, which were invented by Chun T. Rim. Not only the existence of conductive object debris on a Tx coil but also the location of them are determined by an induced voltage difference of the coil sets. By measuring the induced voltage of the coil sets, displacements between a Tx coil and an Rx coil can also be found to inform drivers of their EV alignments. Moreover, the proposed FOD and POD devices do not arise from any power losses in inductive power transfer (IPT).The proposed non‐overlapped coil sets have been demonstrated by simulations and experiments for a prototype coil set. Throughout the experiments, the induced voltage difference of a coil set shows 2.19 mV (ideally zero) without foreign objects while the induced voltage difference significantly increases by 78.2 mV, which is about 35 times that of the value without objects, when eight conductive coins are located on a Tx coil. Also it is found that POD can be achieved by measuring the variation of the induced voltages in coil sets when an Rx coil moves on a Tx coil.This chapter is based on the paper by M.R. Sonapreetha. S.Y. Jeong, S.Y. Choi, and C.T. Rim, “Dual‐purpose non‐overlapped coil sets as foreign object and vehicle location detections for wireless stationary EV Chargers,” in IEEE 2015 WoW , June 2015, pp. 1–7.

In the inductive power transfer systems (IPTS) of wireless electric vehicles (WEV), the electromagnetic field (EMF) should be lowered for the safety of pedestrians. In general, the EMF should be canceled for every space, time, and load condition of interest. Three generalized design methods for canceling the EMF of WEV are explained in this chapter.By adding active EMF cancel coils to each primary main coil and secondary main coil, respectively, the EMF generated from each main coil can be independently canceled by their corresponding cancel coils. Moreover, the EMF can be successfully mitigated if a dominant EMF source only is canceled with a 3 dB margin, which can be applied to any resonant‐type wireless power transfer system. Furthermore, no significant power drop may occur if the cancel coils are placed away from the magnetic coupling path.Design examples are shown for U‐type and W‐type IPTS as well as a wireless stationary EV charger. Experimental verifications are shown for a recently developed I‐type IPTS, which has a narrow rail width structure with alternating magnetic polarity along with a roadway. The proposed design methods have been demonstrated, without a loss of generality, to only the secondary coil, where a relatively large EMF is generated due to high ampere‐turns. An optimum spacing for cancel coils from the main coils and an optimum number of turns are determined. Through experiments, additional EMF mitigation techniques such as the magnetic mirror method, separating pick‐up rectifiers, and passive Al plate are provided. Thus, the EMF at 1 m distance from the center of a pick‐up becomes under 4.4 µT even for the maximum power of 12 kW.This chapter is based on the paper by S.Y. Choi, B.W. Gu, S.W. Lee, W.Y. Lee, J. Huh, and C.T. Rim, “Generalized active EMF cancel methods for wireless electric vehicles,” IEEE Trans. on Power Electronics , vol. 29, no. 11, pp. 5770–5783, November 2014.

In this chapter, the dipole coil inductive power transfer system (IPTS) is applied to a special purpose instrumentation. A highly reliable power and communication system that guarantees the protection of essential instruments in a nuclear power plant (NPP) under a severe accident is explained. Both power and communication lines are established with not only conventional wired channels but also the proposed wireless channels for an emergency reserve. An IPTS is selected due to its robust power transfer characteristics under high temperature, high pressure, and highly humid environments with a number of scattered debris after a severe accident. A thermal insulation box and a glass‐fiber reinforced plastic box are proposed to protect the essential instruments, including vulnerable electronic circuits, from extremely high temperatures of up to 627 ˚C and pressure of up to 5 bar. The proposed wireless power and communication system is experimentally verified by an IPTS prototype having a dipole coil structure and prototype Zigbee modules over a 7 m distance, where both the thermal insulation box and the glass‐fiber reinforced plastic box are fabricated and tested using a high‐temperature chamber. Moreover, an experiment on the effects of a high radiation environment on various electronic devices is conducted based on the radiation test having a maximum accumulated dose of 27 Mrad.This chapter is based on the paper by B.H. Choi, G.C. Jang, S.M. Shin, S.I. Lee, H.K. Kang, and C.T. Rim, “Development of highly reliable power and communication system for essential instruments under severe accidents in NPP,” Nuclear Engineering and Technology , available online, 3 May 2016.

In this chapter, the concept of mobile power electronics is explained with a general classification of this field. The history of mobile power electronics is briefly introduced and a few examples of mobile power electronics such as RF, optical, and tethered power transfer techniques are explained. Conventional wireless power transfer techniques such as inductive power transfer and capacitive power transfer are not dealt with here and will be introduced in Chapter 2.