Next generation microprocessor (Vcore) requirements for high current slew rates and fast transient response together with low output voltage have posed great challenges on voltage regulator (VR) design . Since the debut of Intel 80X86 series, CPUs have greatly improved in performance with a dramatic increase on power consumption. According to the latest Intel VR11 design guidelines , the operational current may ramp up to 140A with typical voltages in the 1.1V to 1.4V range, while the slew rate of the transient current can be as high as 1.9A/ns [1, 2]. Meanwhile, the transient-response requirements are becoming stringer and stringer. This dissertation presents several topics on how to improve transient response for multi-phase voltage regulators. The Adaptive Modulation Control (AMC) is a type of non-linear control method which has proven to be effective in achieving high bandwidth designs as well as stabilizing the control loop during large load transients. It adaptively adjusts control bandwidth by changing the modulation gain, depending on different load conditions. With the AMC, a multiphase voltage regulator can be designed with an aggressively high bandwidth. When in heavy load transients where the loop could be potentially unstable, the bandwidth is lowered. Therefore, the AMC provides an optimal means for robust high-bandwidth design with excellent transient performance. The Error Amplifier Voltage Positioning (EAVP) is proposed to improve transient response by removing undesired spikes and dips after initial transient response. The EAVP works only in a short period of time during transient events without modifying the power stage and changing the control loop gain. It facilitates the error amplifier voltage recovering during transient events, achieving a fast settling time without impact on the whole control loop. Coupled inductors are an emerging topology for computing power supplies as VRs with coupled inductors show dynamic and steady-state advantages over traditional VRs. This dissertation first covers the coupling mechanism in terms of both electrical and reluctance modeling. Since the magnetizing inductance plays an important role in the coupled-inductor operation, a unified State-Space Averaging model is then built for a two-phase coupled-inductor voltage regulator. The DC solutions of the phase currents are derived in order to show the impact of the magnetizing inductance on phase current balancing. A small signal model is obtained based on the state-space-averaging model. The effects of magnetizing inductance on dynamic performance are presented. The limitations of conventional DCR current-sensing for coupled inductors are addressed. Traditional inductor DCR current sensing topology and prior arts fail to extract phase currents for coupled inductors. Two new DCR current sensing topologies for coupled inductors are presented in this dissertation. By implementation of simple RC networks, the proposed topologies can preserve the coupling effect between phases. As a result, accurate phase inductor currents and total current can be sensed, resulting in excellent current and voltage regulation. While coupled-inductor topologies are showing advantages in transient response and are becoming industry practices, they are suffering from low steady-state operating efficiency. Motivated by the challenging transient and efficiency requirements, this dissertation proposes a Full Bridge Coupled Inductor (FBCI) scheme which is able to improve transient response as well as savor high efficiency at (a) steady state. The FBCI can change the circuit configuration under different operational conditions. Its "flexible" topology is able to optimize both transient response and steady-state efficiency. The flexible core configuration makes implementation easy and clear of IP issues. A novel design methodology for planar magnetics based on numerical analysis of electromagnetic fields is offered and successfully applied to the design of low-voltage high power density dc-dc converters. The design methodology features intense use of FEM simulation. The design issues of planar magnetics, including loss mechanism in copper and core, winding design on PCB, core selections, winding arrangements and so on are first reviewed. After that, FEM simulators are introduced to numerically compute the core loss and winding loss. Consequently, a software platform for magnetics design is established, and optimized magnetics can then be achieved. Dynamic voltage scaling (DVS) technology is a common industry practice in optimizing power consumption of microprocessors by dynamically altering the supply voltage under different operational modes, while maintaining the performance requirements. During DVS operation, it is desirable to position the output voltage to a new level commanded by the microprocessor (CPU) with minimum delay. However, voltage deviation and slow settling time usually exist due to large output capacitance and compensation delay in voltage regulators. Although optimal DVS can be achieved by modifying the output capacitance and compensation, this method is limited by constraints from stringent static and dynamic requirements. In this dissertation, the effects of output capacitance and compensation network on DVS operation are discussed in detail. An active compensator scheme is then proposed to ensure smooth transition of the output voltage without change of power stage and compensation during DVS. Simulation and experimental results are included to demonstrate the effectiveness of the proposed scheme.

As a scalable, high-efficiency, and simple converter topology, an interleaved, multiphase buck converter has been widely used to power microprocessors in information industry. As modern microprocessors continuously advance, the required current for high-performance microprocessors used in data center applications could be several hundreds of amperes with a current slew rate larger than 1000 A/μs. This poses great challenges for a high-efficiency, high-power-density voltage regulator design with a fast transient response. On the other hand, the design challenges of voltage regulators in mobile applications are also increasing due to the stringent requirement on the device thickness and the battery life. In a multiphase buck converter, discrete inductors are widely used as energy storage elements. However, this solution has a limited transient response with a large size of magnetic components. To overcome these issues, coupled inductor is proposed to realize a small steady-state current ripple, a fast transient response, and a small inductor size at the same time. Although lots of studies have been conducted in the topic of the coupled inductor, there are still several challenges unsolved in this area. These challenges are addressed through a comprehensive study in this dissertation. First, a comprehensive analysis of different coupled inductor structures is crucial to identify the benefits and limitations of each inductor structure and provide design guidance under different application requirements. Based on the coupling mechanism, different coupled inductor structures are categorized as a direct-coupled inductor (DCL), an indirect-coupled inductor (ICL) or a hybrid-coupled inductor (HCL) in this work. The performance of these three types of coupled inductors is analyzed in detail through the equivalent inductance analysis and the magnetic flux analysis. For the applications that require a small phase number, a DCL can achieve the smallest inductor size with a given inductance requirement. As the phase number increases, it is beneficial to use an ICL and an HCL due to their symmetrical, simple, and scalable inductor structures. As compared to an ICL, an HCL can achieve a smaller inductor size due to the flux-cancellation effect. The difference between a DCL, an ICL and an HCL are revealed quantitively with several design examples through this study. Second, the steady-state inductance (Lss) and the transient inductance (Ltr) are two key design parameters for coupled inductors. A large Lss and a small Ltr are preferred from the circuit performance point of view. However, there is a design conflict in an ICL and an HCL under the inductor size constraint, where reducing Ltr also results in a smaller Lss. A variable coupling coefficient concept is proposed to overcome this issue. With the same Lss, the proposed method can achieve a smaller Ltr during load transients as compared with the conventional method. This concept is realized by applying a nonlinear inductor in the additional winding loop with the current in this loop as the control source. Compared with the conventional structure, the proposed structure can achieve a great output voltage spike reduction and output capacitance reduction. Third, although an ICL and an HCL are promising candidates for multiphase coupled inductors, an extra inductor is required in the additional winding loop to adjust the coupling coefficient. This additional inductor occupies extra space. To shrink the total inductor size, several improved magnetic core structures are proposed to achieve the controllable coupling through the magnetic integration for an ICL and an HCL. Furthermore, the thickness of the core plate can be significantly reduced by the improved core structure for an HCL. Overall, it is demonstrated that the inductor footprint is greatly reduced by the proposed core structure, as compared with the conventional solution. Lastly, a novel PCB-embedded coupled inductor structure is proposed for a 20MHz integrated voltage regulator (IVR) for mobile applications. To achieve a small inductor footprint and a low profile, the inductor structure with a lateral flux pattern and direct coupling is adopted. Compared with the state-of-the-art solution, the proposed structure can adjust the coupling in a simple core structure by changing the inductor winding pattern. The proposed structure integrates multiple inductors into one magnetic core and is embedded into PCB with a total thickness of 0.54 mm. In contrast to prior arts, the proposed inductor structure features a large inductance density and quality factor with a much smaller DC resistance (DCR), thus is seen as a promising candidate for IVR applications. / Doctor of Philosophy / As modern microprocessors continuously advance in the information industry, the required current for high-performance microprocessors used in data center applications could be several hundreds of amperes with a current slew rate larger than 1000 A/μs. This poses great challenges for the power converter design. On the other hand, the design challenges of power converters in mobile applications are also increasing due to the stringent requirement on the device thickness and the battery life. As a scalable, high-efficiency, and simple converter topology, an interleaved, multiphase buck converter has been widely used to power these processors. In a multiphase buck converter, discrete inductors are widely used as energy storage elements. However, this solution has a limited transient response with a large size of magnetic components. To overcome these issues, coupled inductor is proposed to realize a small steady-state current ripple, a fast transient response, and a small inductor size at the same time. Although lots of studies have been conducted in the topic of the coupled inductor, there are still several challenges unsolved in this area. These challenges are addressed through a comprehensive study in this dissertation. First, a comprehensive analysis and comparison of different coupled inductor structures is crucial to identify the benefits and limitations of each inductor structure and provide design guidance under different application requirements. Based on the coupling mechanism, different coupled inductor structures are categorized as a direct-coupled inductor (DCL), an indirect-coupled inductor (ICL) or a hybrid-coupled inductor (HCL) in this work. The performance of these three types of coupled inductors is analyzed in detail through the equivalent inductance analysis and the magnetic flux analysis. The difference between a DCL, an ICL and an HCL are revealed quantitively with several design examples through this study. Second, the steady-state inductance (Lss) and the transient inductance (Ltr) are two key design parameters for coupled inductors. A large Lss and a small Ltr are preferred from the circuit performance point of view. However, there is a design conflict in an ICL and an HCL under the inductor size constraint, where reducing Ltr also results in a smaller Lss. A variable coupling coefficient concept is proposed to overcome this issue. This concept is realized by applying a nonlinear inductor in the conventional structure. Compared with the conventional structure, the proposed structure can achieve a great output voltage spike reduction and output capacitance reduction. Third, although an ICL and an HCL are promising candidates for multiphase coupled inductors, an extra inductor is required in the additional winding loop to adjust the coupling coefficient. This additional inductor occupies extra space. To shrink the total inductor size, several improved magnetic core structures are proposed to achieve the controllable coupling through the magnetic integration for an ICL and an HCL. Lastly, a novel PCB-embedded coupled inductor structure is proposed for a 20MHz integrated voltage regulator (IVR) for mobile applications. Compared with the state-of-the-art solution, the proposed structure can adjust the coupling in a simple core structure by changing the inductor winding pattern. In contrast to prior arts, the proposed inductor structure features a large inductance density and quality factor with a much smaller DC resistance (DCR), thus is seen as a promising candidate for IVR applications.

With the rise of inverter-based resources (IBRs) within the power system, the control of grid-connected converters (GCC) has become pertinent due to the fact they interface IBRs to the grid. The conventional method of control for grid-connected converters (GCCs) such as the voltage-sourced converter (VSC) is through a decoupled control loop in the synchronous reference frame. However, this model-based control method is sensitive to parameter changes causing deterioration in controller performance. Data-driven approaches such as machine learning can be utilized to design controllers that are capable of operating GCCs in various system conditions. This work reviews different machine learning applications in power systems as well as the conventional method of controlling a VSC. It explores a deep learning-based control method for a three-phase grid-connected VSC, specifically utilizing a long short-term memory (LSTM) network for robust control. Simulations of a conventional controlled VSC are conducted using Simulink to collect data for training the LSTM-based controller. The LSTM model is built and trained using the Keras and TensorFlow libraries in Python and tested in Simulink. The performance of the LSTM-based controller is evaluated under different case studies and compared to the conventional method of control. Simulation results demonstrate the effectiveness of this approach by outperforming the conventional controller and maintaining stability under different system parameter changes. / Master of Science / The desire to minimize the use of fossil fuels and reduce carbon footprints has increased the usage of renewable energies also known as inverter-based resources (IBRs) within the power grid. These resources add a level of complexity to operating the grid due to the fluctuating nature of IBRs and are connected to the power grid through grid-connected converters (GCCs). The control method conventionally used for GCCs is derived by accounting for the system parameters, creating a mathematical model under constant parameters. However, the parameters of the system are susceptible to changes under different operating and environmental conditions. This results in poor performance from the controller under various operating conditions due to its inability to be adaptive to the system. Data-driven approaches such as machine learning are becoming increasingly popular for their ability to capture the dynamics of a system with limited knowledge. The different applications of machine learning within power systems include fault diagnosis, energy management, and cyber security. This work explores the use of utilizing deep learning techniques for a robust approach of controlling GCCs.

One of the fundamental characteristics of the microprocessor application is its property of dynamic load change. Although idle most of the time, it wakes up in nanoseconds to support sudden workload demands, which are becoming increasingly severe in today's multi-core processors with large core count. From the standpoint of its voltage regulator (VR) design, it must have very good efficiency at light loads, while also supporting a very fast transient response. Thus, the variable-frequency constant on-time current-mode (COTCM) control scheme is widely used in the VRs, as it can automatically reduce its switching frequency during light-load conditions. But, from transient point of view, it has some limitations in response to heavy-load demands by microprocessors; this is resolved by adding different nonlinear controls in state-of-the-art control schemes. These nonlinear controls are difficult to optimize for the widely variable transient conditions in processors. Another major issue for this ripple-based COTCM control is that when the combined inductor-current ripple in multiphase operation becomes zero because of the ripple-cancellation effect, COTCM loses its controllability. Therefore, the goal of this research is to discover a new adaptive COT control scheme that is concurrently very efficient at light-load conditions and also provides a fast and optimized transient response without adding any nonlinear control; hence providing a complete solution for today's high-performance microprocessors. Firstly, the overview of state-of-the-art COTCM control is discussed in detail, and its limitations are analyzed. Analysis shows that one issue plaguing the COTCM control is its slow transient response in both single and multiphase operation. In this context, two methods have been proposed to improve the transient performance of conventional COTCM control in single and multiphase operations. These two methods can effectively reduce the output capacitor count in system, but the ripple-cancellation and phase overlapping issues in multiphase operation are yet to be improved. This provides motivation to search for a new COT control technique that can resolve all these problems together. Therefore, a new concept of inverse charge constant on-time (IQCOT) control is proposed to replace the conventional ripple-based COTCM; the goals are to improve noise immunity at the ripple-cancellation point without adding any external ramp into the system, and to improve the load step-up transient performance in multiphase operation by achieving natural and linear pulse overlapping without adding any nonlinear control. Additionally, the transient performance of the proposed IQCOT has been further improved by naturally increasing or decreasing the TON time during the load step-up or step-down transient period without adding any nonlinear control. As this transient property is inherent in proposed IQCOT control, it is adaptive to the widely variable transient requirements of processors, and always produces an optimized transient response. In order to design the proposed control with high bandwidth for supporting fast transient response, an accurate high-frequency small-signal model needs to be derived. Therefore, a high-frequency model for the proposed IQCOT control is derived using the describing function method. The model is also verified by simulation and hardware results in different operating conditions. From the derived model it is found that the quality factor (Q) of one double-pole set varies with changes in duty cycle. To overcome this challenge, an auto-tuning method for Q-value control is also proposed in this dissertation. / Ph. D. / High performance microprocessors are the heart of all the fascinating computing devices in use today- ranging from the large servers in data centers to the small smartphones. To supply power to these high performance microprocessors, obviously high performance voltage regulators will be required and the expectations from these voltage regulators are increasing day by day with the complexities of the modern microprocessors. The main focus of this research work is to investigate the state-of-the-art control methodologies of today’s voltage regulators, along with the study of their limitations for future challenging requirements, and therefore, propose some effective methodologies to overcome these limitations. In this regard, a novel control method, called ‘Inverse Charge Constant On-Time (IQCOT)’ control, has been proposed in this dissertation. The concept and the features of this new proposed control scheme, along with the comparison of its benefits with the conventional control methodologies, have been presented in detail in different chapters of this dissertation.

The greening of air transport is the driver for developing technologies to reduce the environmental impact of aviation with the aim of halving the amount of carbon dioxide (COଶ) emitted by air transport, cutting specific emissions of nitrogen oxides (NO୶) by 80% and halving perceived noise by the year 2020. Fuel Cells (FC) play an important role in the new power generation field as inherently clean, efficient and reliable source of power especially when comparing with the traditional fossil-fuel based technologies. The project investigates the feasibility of using an electric hybrid system consisting of a fuel cell and battery to power a small model aircraft (PiperCub J3). In order to meet the desired power requirements at different phases of flight efficiently, a simulation model of the complete system was first developed, consisting of a Proton Exchange Membrane hybrid fuel cell system, 6DoF aircraft model and neural network based controller. The system was then integrated in one simulation environment to run in real-time and finally was also tested in hardware-in-the-loop with real-time control. The control strategy developed is based on a neural network model identification technique; specifically Model Reference Control (MRC), since neural network is well suited to nonlinear systems. To meet the power demands at different phases of flight, the controller controls the battery current and rate of charging/discharging. Three case studies were used to validate and assess the performance of the hybrid system: battery fully charged (high SOC), worst case scenario and taking into account the external factors such as wind speeds and wind direction. In addition, the performance of the Artificial Neural Network Controller was compared to that of a Fuzzy Logic controller. In all cases the fuel cell act as the main power source for the PiperCub J3 aircraft. The tests were carried-out in both simulation and hardware-in-the-loop.

The greening of air transport is the driver for developing technologies to reduce the environmental impact of aviation with the aim of halving the amount of carbon dioxide (COଶ) emitted by air transport, cutting specific emissions of nitrogen oxides (NO୶) by 80% and halving perceived noise by the year 2020. Fuel Cells (FC) play an important role in the new power generation field as inherently clean, efficient and reliable source of power especially when comparing with the traditional fossil-fuel based technologies. The project investigates the feasibility of using an electric hybrid system consisting of a fuel cell and battery to power a small model aircraft (PiperCub J3). In order to meet the desired power requirements at different phases of flight efficiently, a simulation model of the complete system was first developed, consisting of a Proton Exchange Membrane hybrid fuel cell system, 6DoF aircraft model and neural network based controller. The system was then integrated in one simulation environment to run in real-time and finally was also tested in hardware-in-the-loop with real-time control. The control strategy developed is based on a neural network model identification technique; specifically Model Reference Control (MRC), since neural network is well suited to nonlinear systems. To meet the power demands at different phases of flight, the controller controls the battery current and rate of charging/discharging. Three case studies were used to validate and assess the performance of the hybrid system: battery fully charged (high SOC), worst case scenario and taking into account the external factors such as wind speeds and wind direction. In addition, the performance of the Artificial Neural Network Controller was compared to that of a Fuzzy Logic controller. In all cases the fuel cell act as the main power source for the PiperCub J3 aircraft. The tests were carried-out in both simulation and hardware-in-the-loop.

abstract: The increased adoption of Internet-of-Things (IoT) for various applications like smart home, industrial automation, connected vehicles, medical instrumentation, etc. has resulted in a large scale distributed network of sensors, accompanied by their power supply regulator modules, control and data transfer circuitry. Depending on the application, the sensor location can be virtually anywhere and therefore they are typically powered by a localized battery. To ensure long battery-life without replacement, the power consumption of the sensor nodes, the supply regulator and, control and data transmission unit, needs to be very low. Reduction in power consumption in the sensor, control and data transmission is typically done by duty-cycled operation such that they are on periodically only for short bursts of time or turn on only based on a trigger event and are otherwise powered down. These approaches reduce their power consumption significantly and therefore the overall system power is dominated by the consumption in the always-on supply regulator. Besides having low power consumption, supply regulators for such IoT systems also need to have fast transient response to load current changes during a duty-cycled operation. Supply regulation using low quiescent current low dropout (LDO) regulators helps in extending the battery life of such power aware always-on applications with very long standby time. To serve as a supply regulator for such applications, a 1.24 µA quiescent current NMOS low dropout (LDO) is presented in this dissertation. This LDO uses a hybrid bias current generator (HBCG) to boost its bias current and improve the transient response. A scalable bias-current error amplifier with an on-demand buffer drives the NMOS pass device. The error amplifier is powered with an integrated dynamic frequency charge pump to ensure low dropout voltage. A low-power relaxation oscillator (LPRO) generates the charge pump clocks. Switched-capacitor pole tracking (SCPT) compensation scheme is proposed to ensure stability up to maximum load current of 150 mA for a low-ESR output capacitor range of 1 - 47µF. Designed in a 0.25 µm CMOS process, the LDO has an output voltage range of 1V – 3V, a dropout voltage of 240 mV, and a core area of 0.11 mm2. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2018

Active transient voltage compensator (ATVC) has been proposed to improve VR transient response at high slew rate load, which engages in transient periods operating in MHZ to inject high slew rate current in step up load and recovers energy in step down load. Main VR operates in low switching frequency mainly providing DC current. Parallel ATVC has largely reduced conduction and switching losses. Parallel ATVC also reduces the number of VR bulk capacitors. Combined linear and adaptive nonlinear control has been proposed to reduce delay times in the actual controller, which injects one nonlinear signal in transient periods and simplifies the linear controller design. Switching mode current compensator with nonlinear control in secondary side is proposed to eliminate the effect of opotocoupler, which reduces response times and simplifies the linear controller design in isolated DC-DC converters. A novel control method has been carried out in two-stage isolated DC-DC converter to simplify the control scheme and improve the transient response, allowing for high duty cycle operation and large step-down voltage ratio with high efficiency. A balancing winding network composed of small power rating components is used to mitigate the double pole-zero effect in complementary-controlled isolated DC-DC converter, which simplifies the linear control design and improves the transient response without delay time. A parallel post regulator (PPR) is proposed for wide range input isolated DC-DC converter with secondary side control, which provides small part of output power and most of them are handled by unregulated rectifier with high efficiency. PPR is easy to achieve ZVS in primary side both in wide range input and full load range due to 0.5 duty cycle. PPR has reduced conduction loss and reduced voltage rating in the secondary side due to high turn ratio transformer, resulting in up to 8 percent efficiency improvement in the prototype compared to conventional methods.

Materiais piezocompósitos laminados são compostos por camadas de material piezelétrico, metálico e compósito (matriz epóxi com fibras de carbono ou de vidro), que possibilitam obter vantagens em relação aos materiais piezelétricos convencionais, permitindo obter características superiores que não podem ser conseguidas pelos seus componentes de forma isolada como, por exemplo, maior flexibilidade e resistência mecânica ou menor peso. Sob esse enfoque, este trabalho tem por objetivo o desenvolvimento de Estruturas Piezocompósitas Laminadas (EPLA) que consistem basicamente em estruturas multicamadas, através do projeto da sua resposta transiente e harmônica visando aplicações dinâmicas. Entre as potenciais aplicações dessas estruturas, tem-se atuadores, motores, sonares e dispositivos de coleta de energia (\"energy harvester\"), sendo de muito interesse a melhora das suas características dinâmicas e o seu desempenho. O projeto dinâmico de uma EPLA é complexo, porém pode ser sistematizado utilizando o Método de Otimização Topológica (MOT). O MOT é um método baseado na distribuição de material num domínio de projeto fixo com o objetivo de extremizar uma função de custo sujeita às restrições inerentes do problema, combinando algoritmos de otimização e de elementos finitos. A formulação de MOT para o projeto dinâmico de EPLA pretende determinar tanto a topologia ótima dos materiais nas diferentes camadas quanto o sinal de polarização do material piezelétrico e o ângulo da fibra na camada compósita, tendo como finalidade a maximização da amplitude de vibração em pontos determinados (em atuadores) ou da geração de energia elétrica a partir de excitações mecânicas (em coletores de energia). Além disso, é formulado um problema combinando os enfoques harmônico e transiente com o intuito de customizar a resposta da EPLA, de modo que, o nível da resposta seja o mesmo perante diferentes tipos de onda de excitação (transdutores multi-entrada). O trabalho inclui as etapas de projeto, simulação, fabricação e caracterização de protótipos. / Laminated piezocomposite materials are composed by layers of piezoelectric, metal and composite material (epoxy matrix with carbon or glass fiber), which have advantages over conventional piezoelectric materials, because of their superior characteristics, which cannot be achieved by any of its components isolated, for example, more flexibility and strength and less weight. Under this approach, this work aims at the development of Laminated Piezocomposite Structures (LAPS) what primarily consist of multi-layer structures, through the transient and harmonic response design aiming at dynamic applications. Among the potential applications of these structures it can be cited actuators, motors, sonar devices and energy harvester, being of great interest the improvement of its dynamic characteristics and performance. The dynamic design of a LAPS is complex however it can be systematized by using the Topology Optimization Method (TOM). The TOM is a method based on the distribution of material in a fixed design domain with the aim of extremizing a cost function subject to constraints inherent to the problem by means of combining the optimization algorithms and the finite element method (FEM). The TOM formulation for the LAPS dynamic project aims to determine together the optimal topology of the materials for different layers, the polarization sign of the piezoelectric material and the fiber angle of the composite layer, in order to maximize the vibration amplitude at certain points (in actuators), or the generation of electrical energy from mechanical excitations (in energy harvesters). In addition, a TOM problem combining harmonic and transient approaches is formulated with the purpose of customizing EPLA response so that the response level is the same for different excitation waveforms (multi-entry transducers). The work includes design, simulation, manufacturing and characterization of prototypes.

<p>Electromagnetic transients impinging on electromagnetic power devices - such as electric machines, transformers and reactors - can stress the design severely. Thus the magnitudes of the transients are often decisive for the design of the devices. Further, the operation of a device can be transient in itself. This is the case for the explosive magnetic flux compression generator (EMG) and a ferromagnetic actuator. </p><p>Models are presented that are mainly intended for transients in the millisecond range and faster. Hence, eddy currents and the related skin and proximity effect become significant in windings, magnetic cores and in the armatures of the devices. These effects are important for, e.g., the damping of the transients. Further, the displacement current in the insulation of the winding is significant. It changes the response of the windings dramatically, as it manifests the finite velocity of propagation of the electromagnetic fields. Under such circumstances, reflections and excited resonances can make the transient voltage and current distribution highly irregular. </p><p>Induced voltages are modelled with self and mutual inductances or reluctances combined with winding templates. The displacement currents are modelled with capacitances or coefficients of potential. Cauer circuits and their dual form are used to model eddy currents in laminated cores and in conductors. The Cauer circuit enables one to consider hysteresis and the non-linear response of a magnetic core. It is also used to model the eddy currents in the moving armature of an EMG. </p><p>A set-up is presented that can be used to study the transient voltage and the current distribution along a coil. </p><p>The transient response of coaxially insulated windings is analysed and modelled in detail. A lumped circuit model is developed for a coil, Dryformer^TM - the new high-voltage transformer - and Powerformer^TM, the new high-voltage generator. An alternative model, a combined lumped circuit and FEM model, is presented for a coaxially insulated winding in two slot cores.</p>