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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%. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The tolerances and limitations in design and manufacturing of both electrical motors and inverters lead to parasitic resistances in the phases. Therefore, the phase resistances are asymmetric, which causes an asymmetry among the phase currents and a resulting increase in torque ripple. This paper proposes a novel scheme for torque ripple minimization using online estimation of unbalanced stator resistances of a permanent-magnet synchronous motor. The identifiability of the stator resistances in a nonlinear model is investigated by employing a sensitivity analysis. The phase resistances are estimated by recursive least squares in the rotating reference frame in real time. Using the estimated resistances, torque ripple reduction is achieved by a compensation scheme in the stationary reference frame. The effectiveness of the proposed scheme is verified in both simulation and test-bench experiments. Results with and without consideration of magnetic saturation are compared. [ABSTRACT FROM PUBLISHER]

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 Bayerische Motoren Werke AG (BMW) i3. [ABSTRACT FROM AUTHOR]

• Analytic approximation by multiple Taylor series expansions. • Unlimited spatial area with high accuracy is achieved. • A fast evaluation of the magnetic field for every point in space can be done. • Accuracy depends on the distance of the evaluation point to the current loop. In the wide field of contactless energy transfer over a large distance, e.g. for charging electric vehicles or for supplying energy to implanted medical devices in the human body, different types of coils are used. For being able to determine the properties of the path of energy transfer, the spatial distribution of the generated magnetic field is very important. An analytic expression has several advantages for determining the spatial distribution of the magnetic field in an efficient way. In this paper, an analytic approximation for the vector potential and the magnetic flux density of a filamentary circular current loop is proposed. The derivation of the fundamental equations and the concept of the approximation is presented and the range of parameters, in which an analytic solution with sufficient precision is obtained, is determined and evaluated dependent on the parameters of the design and the approximation. The results of the analytic approximation for the magnetic flux density are presented based on an exemplary filamentary circular current loop. Finally, the results are verified by a FEM simulation. The analytic approximation shows a sufficient accuracy at large distances as well as in the close vicinity of the current loop and turns out to be a fast and efficient option to evaluate the magnetic field of one or more circular coils. [ABSTRACT FROM AUTHOR]

A reliable simulation and design of inductive components requires knowledge of the core material's magnetic properties. Usually no such data is available for medium frequencies, thus magnetic properties have to be measured. IEC 60404-10 suggests to measure magnetic properties in a frequency range between 400 Hz and 10 kHz by means of an Epstein frame, which however requires high apparent power [1]. Furthermore the mean magnetic path length has to be known to measure the magnetic field strength. Standards such as IEC 60404-10 state a constant length of 940 mm which in reality depends on multiple factors, including frequency and peak flux density. Therefore errors will inevitably be made [2,3]. Singe sheet testers, which are not as popular as Epstein frames, however have some advantages over the Epstein frame [1,2,4,5]. To decrease the apparent power demand when measuring Epstein frame sized samples as well as to reduce systematical errors, an optimized single sheet tester, also called single strip tester or SStT, has been developed for medium frequencies and high flux densities. [ABSTRACT FROM AUTHOR]

This article focuses on increasing the computational efficiency of 3D multi-static magnetic finite element analysis (FEA) for electrical machines (EMs), which have a magnetic field evolving in 3D space. Although 3D FEA is crucial for analyzing these machines and their operational behavior, it is computationally expensive. A novel approach is proposed in order to solve the magnetic field equations by exclusively using the magnetic scalar potential. For this purpose, virtual variable permanent magnets (vPMs) are introduced to model the impact of the machine's coils. The effect on which this approach is based is derived from and explained by Maxwell's equations. To validate the new approach, an axial flux machine (AFM) is simulated using both 2D and 3D FEA with the magnetic vector potential and current-carrying coils as a reference. The results demonstrate a high level of agreement between the new approach and the reference simulations as well as an acceleration of the computation by a factor of 15 or even more. Additionally, the research provides valuable insights into meshing techniques and torque calculation for EMs in FEA. [ABSTRACT FROM AUTHOR]

This article proposes an online diagnosis scheme for transistor faults of asymmetric half-bridge converter (AHBC) in switched reluctance motor (SRM) drives. In order to extract more information from the phase current to identify faults, based on the conventional current measurement method, two novel current measurement methods are presented by reconstructing current sensors. According to the novel current measurement methods, a current prediction method is raised. The phase current at the kth sampling time is available so that the estimated current can be calculated. The fault can be detected and located by analyzing the given and actual switching states, which are deduced by comparing the measured and estimated currents. Compared with existing methods, the proposed scheme can be applied to diagnosis of multiple faults in n-phase AHBC, which can operate at various control strategies and chopping modes. With a single current sensor in each phase, the scheme will not increase the cost and complexity of the SRM drive. Furthermore, the scheme does not require complicated computation, making it easy to implement online. The experimental results confirm the effectiveness and flexibility of the proposed scheme. [ABSTRACT FROM AUTHOR]

A novel method to suppress the force ripple of switched reluctance linear motors (SRLMs) based on predictive-fuzzy control is proposed in this article. Generally, the force ripple mainly occurs in the commutation area, resulting from the dropping force of the outgoing phase that cannot match the rising force of the incoming phase. The force distribution function (FDF) is a suitable method for controlling the forces of the outgoing phase and incoming forces during the commutation area. However, the controller calculation takes time and the motor shows inductive behavior, so the control signal, which is the reference current in FDF, always lags the reference force, which weakens the effect of the FDF control. Considering this problem, a method of predictive-fuzzy control is proposed in this article. The current can be controlled in advance by predicting the force, which reduces the appearance of the negative electromagnetic force, which is beneficial to improving the efficiency of the motor, and the mutual inductance is also considered in the predictive model. Additionally, a fuzzy controller is employed, and adaptive parameters of the control system are adopted. To validate the proposed control system, experimental verification is performed on a 500 W 6/4 double-sided SRLM, showing that the proposed method has a better force ripple suppression performance than the FDF control. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this contribution, a design procedure that is applicable to many kinds of wireless or contactless energy transfer systems is proposed. The design procedure is limited to near field wireless energy transfer systems in resonant operation. For this purpose, the input impedance and voltage transfer function of different natural frequencies are calculated analytically, and moreover, the behavior of the system is described. Following three issues lead to a readily applicable design procedure. First, the knowledge of the transfer functions. Secondly, the knowledge of basic magnetic properties and lastly, the known influence of harmonics according to rectifier and inverter. This design procedure is demonstrated with two hardware setups. [ABSTRACT FROM AUTHOR]

Generators in wind turbines are the key components to convert mechanical into electrical power. They are subject to electrical and mechanical excitation at the same time, which can cause electro-mechanical interactions. To avoid unwanted interactions, standard design approaches use conservative, stiff designs that lead to heavy generators of several hundred tons. New wind turbine designs, beyond 10 MW, need to revisit the conservative design approach as the tower top mass needs to be limited. To reduce the generator's mass without large deformation that can damage the wind turbine, a better understanding of electro-mechanical interactions is key. This requires a detailed model including both the mechanical and the magnetic forces. This work presents a numerical setup of a coupled electromagnetic-structural multi-body model. While existing couplings are application-specific; the presented coupling is independent of the actual use case and allows for transient dynamic two-way coupled analyses. For validation, an experimental setup with basic components is introduced. The results show the applicability of the developed coupling for detailed analysis of general electro-mechanical interactions. [ABSTRACT FROM AUTHOR]