An electrically excited synchronous machine (EESM) is a promising alternative to the permanent magnets synchronous machines being used in the automotive industry. However, the main disadvantage of the EESM with the conventional excitation system with brushes is the presence of slip rings on the shaft, which need regular maintenance. A promising alternative to the conventional excitation system of the EESM is a wireless power transfer (WPT) system. In this paper, we focused on WPT excitation system based on the rotary transformers. First, the model of the EESM in the d-q reference frame with vector control system has been built (based on the parameters of the real machine) and analyzed using MATLAB/Simulink software. Second, the influence of the rotary transformer design parameters on the dynamic performance of the EESM has been investigated. Finally, different topologies of the rotary transformers found in the literature have been analyzed, modeled and compared using an analytical and numerical approach. Based on the obtained results, the most suitable electrical parameters (i.e., geometry parameters, supply frequency, magnetizing and leakage inductance, winding resistance and efficiency) of the rotary transformer have been identified and implemented into the d-q model of EESM.

In this article, the influence of the rotary transformer design parameters on the dynamic performance of the electrically excited synchronous machine (EESM) has been investigated. The model of EESM in the d-q reference frame with the control system has been built and analyzed using Matlab/Simulink software. The main electrical parameters of the rotary transformer were identified and implemented into the equivalent circuit model of EESM based on the parameters of the real machine. Based on the proposed model, the most suitable design parameters for the wireless excitation system were obtained.

The quality and efficiency of electrical machines are key factors towards improvement of the drive performance. Manufacturing processes have a significant impact on the efficiency of electrical machines. There are different manufacturing techniques such as mechanical cutting, laser cutting, electrical discharge machining etc. Each cutting techniques may cause a deformation near edges of the cutting area that may severely affect the properties of the B-H curve of the ferromagnetic materials. Thus it is important to predict approximately the extension of the damaged area. In this study we have developed an approach based on finite element method using COMSOL Multiphysics simulation software to evaluate the deformation caused by laser cutting on the edges of the ferromagnetic material.

Laser cutting is one of the very well-known techniques to manufacture electrical machines. The edges of the stator and rotor lamina influenced by the laser cutting become degraded areas after the cutting process. The B-H curve of the ferromagnetic material are deteriorated because of the laser cutting as well. In this paper, we present the state of the art for the laser cutting and thermal influence on the electrical machine characteristics. As well as the novel approach for the electrical machine properties modelling, including technology-thermal-magnetic cross effect.

Three different methodologies for inductance calculation in the direct and quadrature magnetic axis are presented: first; based on machine phasor diagram, second; using magneto-static calculations and third; frozen permeability approach. All three are being used for inductance calculation of interior permanent-magnet machine and are based on the two-dimensional finite-element method. In this paper, the results obtained by using presented approaches are validated and compared.

The aim of the paper is to show the importance of paying an attention to precisely manufacture electric machines. The study is done on axial flux permanent magnet prototype machine. The model has also been analyzed by using 3D finite element method. During generator mode no-load testing of the prototype machine, high unexpected overheating of the rotor discs was revealed. Further investigations showed that the cause of the heating were misalignments in the machine prototype production.

The paper presents an approach to model shorted turns in rotor excitation winding of synchronous generator using finite element analysis. It enables detailed examination of magnetic field at several operating conditions under healthy and faulty states which are difficult or even impossible to carry out by available measurement methods in industrial environment. It is confirmed that an extensive analysis should be performed to assure accurate healthy/faulty state predictions, since the level of diagnostic signal is considerably influenced by a combination of many machine design and operating parameters.

The paper presents estimation of parameters alternation in a three-phase induction motor due to broken rotor bars, which cause electric and magnetic asymmetry in the machine. Using d-q model of induction motor this asymmetry is reflected as pseudo-saliency through different resistances and inductances in both axes. An extensive study has been performed to simulate various cases of faulty cage, which cannot be achieved by measurements on actual industrial drives. Simulation results can be efficiently used for analysis of closed-loop induction motor drives, in which determination of rotor faults, due to the intrinsic speed correction performed by the controller, is much harder to achieve.

This paper describes the evaluation of parameters of a three-phase induction motor with broken rotor bars. Using standard d-q model of induction motor the electric and magnetic asymmetry can be expressed through differently modified rotor parameters in both axes. A non-standard, one-phase measuring method was employed. To assess the measurement results of the method and to predict various situations which can not be achieved by measurements an extensive finite element analysis has been performed. Streszczenie. Niniejszy artykul opisuje ocene parametrow trojfazowego silnika indukcyjnego z peknietym pretem wirnika. Za pomocą standardowego modelu d-q silnika indukcyjnego, elektryczna i magnetyczna asymetria moze byc wyrazona przez inne zmodyfikowane parametry wirnika w obu osiach. Zastosowana zostala niestandardowa, jednofazowa metoda pomiaru. W celu oceny wynikow pomiarow metody i zapobiegania roznym sytuacjom niemozliwym do zmierzenia zastosowano obszerną analize elementow skonczonych. (Estymacja parametrow silnika indukcyjnego z uszkodzonym wirnikiem)

This paper describes the evaluation of parameters of a three-phase induction motor with broken rotor bars. Such fault causes electric and magnetic asymmetry in the machine. Using standard d-q model of induction motor this asymmetry can be expressed through differently modified rotor parameters in both axes. In pursuing the goal to establish accurate motor parameters, a non-standard, one-phase measuring method was employed. In this way angle dependence of rotor parameters following a sinusoidal shape was determined. Additionally to measurements an extensive finite element analysis has been performed for two purposes. Firstly, to assess the measurement results of the method and, secondly, to predict various situations which can not be easily achieved by measurements due to hardware limitations (e.g. different numbers of broken bars). Finite element analysis evidences the correctness of the machine parameters obtained from proposed measurement method.

The paper presents an approach to modeling of shorted turns in rotor excitation winding of synchronous generator using FEM. It enables detailed analysis of magnetic field at several operating conditions under healthy and faulty states which are difficult to carry out by available measurement methods in industrial environment. Modeling of excitation winding faults is performed for a 156 MVA turbo generator operating in thermal power plant. Since the level of diagnostic signal is considerably influenced by combination of many machine and operating parameters, an extensive analyses are needed to assure accurate healthy/faulty state predictions.

The aim of this paper is to present parametric nonlinear reluctance model of outer rotor permanent magnet transverse flux machine (TFM). Main and leakage magnetic flux paths of TFM are studied and modelled with reluctances using mean length and cross area approximation which divide the model into simple solids. General propose circuit simulator is used to solve the model. The main goal of the model is to provide the results of machine performances with sufficient accuracy and quick enough to use them in optimization procedures.

Since the interlamination short-circuits in stator cores can cause major damage to electrical machine a great emphasis is placed to detect such faults. ELCID (Electromagnetic Core Imperfection Detector) test is nowadays often used for testing of interlamination insulation in stator cores of large electrical machines. To investigate this relatively young method a laboratory model of stator core was built, which enables measurements and analyses of intentional short-circuits in the core. Interlamination faults were also simulated and analysed using FEM.

In this paper a method for parameter detection through a single phase measurement in a three phase induction machine with broken rotor bars, is presented. Based on frequency response of the machine, the parameters can be obtained with only two measurements. In order to study the variation of these parameters with position of electrical rotor asymmetry a single phase measurement at standstill is proposed. Simulations and experimental measurements confirm the theoretical assumptions. Streszczenie. W artykule przedstawiono metode detekcji parametrow przez uzycie jednofazowego pomiaru w trojfazowej maszynie indukcyjnej z peknietym pretem wirnika. Wykorzystując odpowiedź czestotliwościową, parametry mogą byc wyznaczone w dwoch pomiarach. W celu przebadania zmienności tych parametrow w zalezności od elektrycznej asymetrii wirnika jednofazowy pomiar w stanie zatrzymanych jest przeprowadzany. Symulacje i pomiary potwierdzają zalozenia teoretyczne. (Estymacja parametrow przy uzyciu jednofazowego pomiaru trojfazowej maszyny elektrycznej)

The aim of proposed paper is to present the magnetic field calculation in aerial toroidal and poloidal coil systems arrangement. The magnetic system is in principal very similar to the Tokamak configuration. The coil models have been done in 2-D axisymmetry [l] and/or in 3-D [2], depending on geometric arrangement and excitation of coils. The finite element method (FEM) was used in all analyses. The calculation of 2-D and 3-D electromagnetic quantities were performed in Magneto-static mode and also in magneto-transient mode coupled with external circuit. Poloidal coil arrangement and magnetic field calculation were performed in 2-D axisymmetry in magneto-static mode. Meanwhile, the toroidal coil system requires a 3-D geometric model description.

In this paper, a simplified two-axis model for induction machines with electrical rotor faults is derived. The model is intended for analysis of the impact of rotor fault on control loop with inverter fed induction machines, therefore detailed modeling of internal states of the machine is not required. The model is derived from unified theory of electrical machines, where rotor parameters are asymmetrical. The assumptions made during the development of the model are confirmed by experimental measurements. Finally, the comparison between proposed simplified model and detailed induction machine model is performed. The comparison shows very good agreement between simplified and detailed induction machine model, thus making the proposed model suitable for simulations of rotor faults.

The paper presents an approach to modeling of shorted turns in rotor field winding of synchronous generator using finite element method. It enables detailed analysis of magnetic field at several operating conditions under healthy and faulty states which are difficult or even impossible to carry out by available measurement methods in industrial environment. Modeling of field winding faults are performed for both typical generator designs - turbo and hydro, and analysis reveals some differences, which are significant for practical use in fault detection procedures. It is confirmed that an extensive analysis should be performed to assure accurate healthy/faulty state predictions, since the level of diagnostic signal is considerably influenced by a combination of many machine and operating parameters. The scheme of developed on-line diagnostic system with its hardware and software concept is also presented and discussed.

Electric field and dielectric conditions were analysed in an oil immersed power transformer. The particularity of the transformer's design we are dealing with is an attempt to eliminate the stress-control ring above the low voltage (LV) winding. Using the finite element method (FEM) we analysed the steady state electric field that suited conditions during dielectric test with a separate AC source. In the paper is also discussed the evaluation and analyses of other possibilities to form an adequate electric field with simple constructional elements at the ends of the windings. Therefore we evaluated the influence that the radius of conductors, thickness of paper insulation, and additional insulation elements have on electric field strength in the critical places.

The paper presents calculation of linear induction motor and linear synchronous motor steady- state characteristics using finite element method. 2D non-linear magnetostatic and eddy-current solver were used for magnetic field and force calculation. A detailed insight in magnetic field distribution and produced output force is a basic step for evaluation of motor performance. Calculations were performed for different excitation currents and different air gap lengths for both types of linear motor. The results obtained from the magnetic field calculations could also be used for determination of motor parameters (e.g. inductance) useful for mathematical modelling and control system simulations.

Some methods which were used for calculation of power losses in ultra a high speed PM motor with a 2D FEM software are presented. Using manufacturer's data of power losses for ferromagnetic materials and/or solutions of magnetic analyses, Power losses in stator eve, rotor poles and stator windings were calculated, Calculations made by 2D FEM software helped lis to determine and analyse those losses for different materials, designs and operating conditions. Since the FEM software is widely used for designing of electrical machines, these methods Present quite good alternatives for power loss calculation ill ferromagnetic cores and conducting Parts of the machines.