This paper deals with the design, the setup, and the operation of a rotating contactless energy transfer (CET) system. The system is used to replace the slip rings of an electrical excited ...synchronous machine and to transfer energy onto the rotor of the machine without mechanical contact. A compensation topology with an autoresonant circuit to generate the high frequency voltage is presented. Furthermore, the required parameters of the CET system are calculated. Based on these calculations, the system consisting of the power electronics, the compensation network, the magnetic path, the control system, and the electrical excited synchronous machine with controller, is set up. Finally, the calculated parameters are verified by measurements.
For applications with high torque demand, gearboxes are commonly used to convert torque and speed in order to receive higher specific values for torque and power. This causes additional losses, cost, ...inaccuracies, effort, and noise. Eliminating the need of a mechanical gear and the associated disadvantages, Transverse Flux Machines with their high torque density are a very promising alternative. Despite a high torque density and a high efficiency, these types of machines are not commonly used. Due to the complex structure, challenges with mechanical design, and modeling of the machine behavior arise. Additionally, there are high requirements for the inverter due to the low power factor. This paper provides an overview of the state of the art including the potentials and advantages but also the problems and hindrances of these types of machines. Relating to linear and rotary machines from research and industry, the machine is introduced with its history, application and classification. Further, the general technical aspects, the influence of materials for flux guidance, the methods of modeling, methods for a minimization of torque ripples, as well as methods for power factor improvement are presented.
Millimeter-sized devices, which are implanted within tumors by a minimally invasive operation technique, are very promising for tumor treatment with a contactless thermal ablation procedure. These ...implanted devices are heated from outside of the patients' body by an alternating magnetic field. For minimizing unwanted influencing and heating of healthy tissue and other devices inside the patients' body, the ratio of generated heating power within the implanted devices to required magnetic field strength has to be maximized. In this paper, the heating power generated by eddy currents within solid and electrically conductive implanted devices, whose dimensions are restricted by the minimally invasive operation technique, is analyzed and optimized based on a combination of numerical and analytic calculations for different parameter sets of material and magnetic field properties. The parameters for achieving maximum heating power are presented along with the dependency of the heating power on these parameters. The results are validated by experimental prototype measurements. Furthermore, the specific absorption rate is evaluated based on specific coil configurations for generating the alternating magnetic field. This paper shows the feasibility of significantly increasing the heating power of solid and electrically conductive implanted devices by choosing the appropriate properties of the implant material. This enhances the safety and the well-being of the patients and represents a great benefit for the outcome of the tumor treatment.
This article deals with a LCC-LCC compensated dynamic wireless power transfer system for electric vehicle charging applications. The presented prototype system allows for a power transfer of about 10 ...kW at 20 cm coil copper to copper distance. With just one circular pickup coil and a very straightforward control scheme, a new coil arrangement enables a seamless power transfer. Furthermore, the system’s design power level is easily adjustable by the size of the the pickup coil. The hardware architecture as well as the software functionality are described in detail. A 20 m test track was built up according to the outlined principle. By measuring the transmitted power, the efficiency and the interference between the primary segments and its effect on the inverter currents are examined. The results show an effective DC to DC efficiency in the range of 91 to 92% and a power fluctuation of approximately 25%.
The demand for electric machines has been rising steadily for several years—mainly due to the move away from the combustion engine. Synchronous motors with rare earth permanent magnets are widely ...used due to their high power densities. These magnets are cost-intensive, cost-sensitive and often environmentally harmful. In addition to dispensing with permanent magnets, electrically excited synchronous machines offer the advantage of an adjustable excitation and, thus, a higher efficiency in the partial load range in field weakening operation. Field weakening operation is relevant for the application of vehicle traction drive. The challenge of this machine type is the need for an electrical power transfer system, usually achieved with slip rings. Slip rings wear out, generate dust and are limited in power density and maximum speed due to vibrations. This article addresses an electrically excited synchronous machine with a wireless power transfer onto the rotor. From the outset, the machine is designed with a wireless power transfer system for use in a medium-sized electric vehicle. As an example, the requirements are derived from the BMW’s i3. The wireless power transfer system is integrated into the hollow shaft of the rotor. Unused space is thus utilized. The overall system is optimized for high efficiency, especially for partial load at medium speed, with an operation point-depending optimization method. The results are compared with the reference permanent magnet excited machine. A prototype of the machine is built and measured on the test bench. The measured efficiency of the inductive electrically excited synchronous machine is up to 4% higher than that of the reference machine of the BMW i3.
This paper presents the design of a bidirectional wireless power and information transfer system. The wireless information transfer is based on near-field technology, utilizing communication coils ...integrated into power transfer coils. Compared with conventional far-field-based communication methods (e.g., Bluetooth and WLAN), the proposed near-field-based communication method provides a peer-to-peer feature, as well as lower latency, which enables the simple paring of a transmitter and a receiver for power transfer and the real-time updating of control parameters. Using the established communication, control parameters are transmitted from one side of the system to another side, and the co-control of the inverter and the active rectifier is realized. In addition, this work innovatively presents the communication-signal-based synchronization of an inverter and a rectifier, which requires no AC current sensing in the power path and no complex algorithm for stabilization, unlike conventional current-based synchronization methods. The proposed information and power transfer system was measured under different operating conditions, including aligned and misaligned positions, operating points with different charging powers, and forward and reverse power transfer. The results show that the presented prototype allows a bidirectional power transfer of up to 1.2 kW, and efficiency above 90% for the power ranges from 0.6 kW to 1.2 kW was obtained. Furthermore, the integrated communication is robust to the crosstalk from the power transfer and misalignment, and a zero BER (bit error rate) and ultra-low latency of 15.36 µs are achieved. The presented work thus provides a novel solution to the synchronization and real-time co-control of an active rectifier and an inverter in a wireless power transfer system, utilizing integrated near-field-based communication.
Minimally invasive thermal ablation procedures of tumors with implanted devices are very promising, especially for the repetitive treatment of deep-seated tumors. The implanted devices are heated ...without contact by an alternating magnetic field from outside the patient's body. In this paper, the heating power of millimeter-sized implanted coils is analyzed and optimized with a numerical-analytic analysis and the dependencies on spatial, electrical, and magnetic parameters are evaluated and presented for being able to choose the optimum implanted coil for a specific set of parameters. The analysis is done with focus on the implanted coils based on a homogeneous alternating magnetic field. A heating power of 1.5 W required for achieving an adequate rise of tissue temperature is determined in a thermal analysis and the corresponding specific absorption rate (SAR) is evaluated along with the power transfer efficiency (PTE) and the coupling coefficient for different types of implanted coils. For uncompensated implanted coils, a SAR of 306 mW/kg, a PTE of <inline-formula> <tex-math notation="LaTeX">\mathrm {4.62\cdot 10^{-3}} </tex-math></inline-formula> and a coupling coefficient of <inline-formula> <tex-math notation="LaTeX">\mathrm {2.49\cdot 10^{-3}} </tex-math></inline-formula> is achieved by a magnetic field strength of 1727 A/m, whereas a SAR of 1.84 mW/kg, a PTE of <inline-formula> <tex-math notation="LaTeX">\mathrm {436\cdot 10^{-3}} </tex-math></inline-formula> and a coupling coefficient of <inline-formula> <tex-math notation="LaTeX">\mathrm {2.3\cdot 10^{-3}} </tex-math></inline-formula> is achieved by a magnetic field strength of 134 A/m for serial compensated implanted coils. With this, the ratio of heating power to required magnetic field strength is maximized, which reduces the risk of unwanted heating of healthy tissue and other implanted devices and therefore enhances the safety as well as the well-being of the patients.
The use of wide bandgap (WBG) semiconductor devices, which enable higher switching slew rates, and the increase in DC link voltage, which provides system-wide advantages, exposes the winding system ...of traction machines to enhanced electrical stress. The resulting nonlinear voltage distribution along the motor winding favors partial discharges (PD), which in low voltage (LV) machines causes excessive damage to the insulation system, and premature failure can occur. A simple solution by increasing the enamel thickness of the wires leads on the one hand to a lower copper fill factor. On the other hand, this measure is not necessarily accompanied by an increase in electrical resilience in the case of pulsed voltage. It is therefore essential to understand the phenomenon of partial discharges, which is composed of a large number of processes and mechanisms, to be able to make an estimation of aging. The ultimate goal is to derive a lifetime model that links the dynamic load collectives - ideally in conjunction with the environmental stress influences - of a traction application to a usage-dependent and realistic prediction of the residual lifetime. To this end, this paper provides an overview of the current state of science and technology in this interdisciplinary topic by describing, with reference to high voltage (HV) technology/engineering, the design of the insulation system, the discharge physics, the degradation mechanisms, the statistical effects to be considered, and the partial discharge measurement methods.
This paper mainly takes a 6/4 switched reluctance motor (SRM) as an example to analyze the temperature of the motor. In order to establish the equivalent thermal circuit model (ETCM) conveniently, ...the mechanical structure of the motor is simplified to a certain extent, and the characteristic nodes are divided. Then the heat transfer process in the rotor region, the stator region and the whole motor during the operation of the motor is analyzed, and the ETCM of those regions are established respectively. This method of establishing ETCM is also applicable to superconducting motors. Based on the basic principles of heat transfer, the calculation method of thermal resistance in each ETCM is given in this paper. Then, the three-dimensional (3-D) finite element (FE) temperature field model of the motor is built and compared with the ETCM. Finally, the accuracy of the ETCM is verified by experiments.
This paper answers the research question: Can the contactless induced energy supply from a novel inductive floor be used to navigate omnidirectional automated guided vehicles (AGVs)?
In contrast to ...existing systems a novel inductive floor enables AGVs traveling through production without charging breaks. This floor consists of tiles with inductive modules, which supply the AGV with energy. In addition to supplying power to the AGV, the inductive modules are also intended to guide the vehicle through production. To enable such a guidance sensors placed in the AGV measure the induced voltages of the floor. To answer the research question these voltages are calculated with the help of an electromagnetic simulation of the AGV’s travel on the inductive tiles. To estimate the position as well as rotation of the AGV depending on the simulated voltages as inputs a novel algorithm is presented. During the travel the AGV is able to move in arbitrary directions independently of its orientation. To control the omnidrectional AGV consistently without singularities, a transformation in Omni-Curve-Parameters (OCP) is proposed. As simulation case study a four wheeled steering- and velocity controlled AGV is introduced. For the evaluation a novel motion model depending on the input OCP is presented. This model is compared to the estimation of the position to verify the accuracy and the reproducibility of the algorithm.
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