Aleksander Kilk

Cogging torque reduction methods

This paper considers the study of methods for reduction of the cogging torque in permanent magnet machines. Cogging torque has been analyzed to be reduced by slot skewing, width of slot opening, magnet pole radius and also by mounting of the magnets. Electromagnetic simulations of the PM generator were performed by using finite element analysis. Virtual torque method has been used for calculation of the cogging torque.

Magnetic properties of reduced Dy NdFeB permanent magnets and their usage in electrical machines

This paper describes the magnetic properties of different permanent magnet materials and their industrial usage as crucial components of permanent magnet electric machines. As the prices of rare earth materials, especially neodymium-iron-boron (NdFeB), has been rising rapidly during the last few years and has been quite unstable during the past decade, the search of new cheaper and yet durable alloys has started. One of the possibilities of cutting the price of NdFeB alloys is the decreasing of the dysprosium (Dy) content of such material. Possibilities of using these new materials in electrical machines as well as potential risks are analyzed in the paper. An overview of the development of low Dy magnets is presented. Necessity of further investigations is pointed out.

Analysis of permanent magnet multipole synchronous generators for wind applications

Analysis of tendencies in development of wind power industry for last decade has been presented. Synchro- nous generators with permanent magnet excitation for direct- drive wind power turbines are described. Analysis of magnetic field distribution for design of a low-speed multipole synchro- nous generator with radial magnetic flux and permanent magnet excitation has been presented. The test results of a prototype PM generator are analyzed and compared with the calculated characteristics and data.

Analysis of the eccentricity in a low-speed slotless permanent-magnet wind generator

This paper presents the analytical analysis of different eccentricities in the rotor of a novel slotless wind power generator. The analytical expressions for the air gap eccentricity have been derived and the effects of these eccentricities on the air gap flux density, the resultant unbalanced magnetic pull and the induced emf are investigated. The analysis shows a strong pull in the case of static eccentricity, which is not seen when the case of elliptic eccentricity for example. The analysis shows also that the induced emf per coil can vary very much but due to the series connection of the coil per phase emf is uniform but has higher rms value than in the case of healthy machine. The analytical equations are verified for the case of healthy machine on a constructed laboratory prototype.

Exterior-rotor permanent magnet synchronous machine with toroidal windings for unmanned aerial vehicles

This paper represents the study of the multimode permanent magnet synchronous machine constructed for a small-sized unmanned aircraft. An overview of commonly used electrical machine types for unmanned aircrafts is also given within this paper. The main objective of the research was to create an electrical machine that could be used in addition to the combustion engine as a motor-generator. Based on the specifics of the area and the goal of the research the most suitable and optimal solution of the machine topology is considered. The paper gives an overview of the design of the permanent magnet electrical machine and its mechanical and electrical parameters. The test bench for experimental study of the prototype permanent magnet machine was also designed and built. Using the test bench the no-load test was carried out and corresponding characteristics were charted in a generator mode of the machine.

Lifecycle-based design and optimization of electrical motor-drives - Challenges and possibilities

This paper describes the procedure of lifecycle-based design and optimization of electrical motor-drives as well as related methodologies to be developed. As the electric motor-drives are the most electrical energy consuming apparatuses, thorough and in depth optimization of the drives during their design process is essential to support energy efficient and environmental friendly development in electrical engineering and industry processes. Lifecycle-based optimization would grant a possibility to evaluate a wider range of variables that affect the environment and energy consummation of the drives. An overview of existing optimization techniques and related literature is presented. Necessity of new methodologies is pointed out.

Study and verification of a slow speed PM generator with outer rotor for small scale wind turbines

This paper considers the study of a directly driven low-speed permanent magnet synchronous generator specially constructed for a vertical axis wind turbine. The studied PM generator with outer rotor construction offers an alternative to fix the wind turbine directly to the end-disk of rotor. As an advantage of the outer rotor PM generator construction it is easier and more reliable to fix the magnets on the rotor active surface. An analysis to optimize the active length of both stator magnetic core and air-gap has been presented. Cogging torque has been analyzed to reduce it by slot skewing. Electromagnetic simulations of the PM generator were performed by using finite element analysis and the SPEED software. A 5 kVA PM generator was designed, manufactured and tested. The test results of the prototype PM generator have been analyzed and compared with the calculated characteristics and data.

Sensorless Detection of Induction Motor Rotor Faults Using the Clarke Vector Approach

Sensorless Detection of Induction Motor Rotor Faults Using the Clarke Vector Approach Due to their rugged build, simplicity and cost effective performance, induction motors are used in a vast number of industries, where they play a significant role in responsible operations, where faults and downtimes are either not desirable or even unthinkable. As different faults can affect the performance of the induction motors, among them broken rotor bars, it is important to have a certain condition monitoring or diagnostic system that is guarding the state of the motor. This paper deals with induction motor broken rotor bars detection, using Clarke vector approach.

Detection of broken bars in frequency converter fed induction motor using Park's vector approach

This paper presents the experimental study of induction motor broken rotor bars diagnostics. Fault tests are performed on a machine with 3 broken bars, driven through a frequency converter. Parks vector approach is used as an analyzing tool to detect the broken rotor bars. Parks vector patterns in case of stator current and voltage are investigated. Results of the tests and discussion are presented. Necessity for further study is pointed out.

Analysis and prototyping of a low-speed small scale permanent magnet generator for wind power applications

Many companies engaged in wind generator development are investigating permanent magnet generators (PMG) mainly because of higher efficiency over a broad range of wind speed and reduced costs of maintenance. One important parameter of PM generators is the primary magnetic flux that has certain influence to no load voltage of the machine. Thus, needs for efficient calculation methods for primary magnetic field is required. Finite element method is one of the most common and efficient way to analyze the magnetic flux of the machine. But on the other hand it is relatively complicated calculation method and it might be incomprehensible. Analytic calculation or calculations based on reluctance network are comprehensive and suitable for engineers-designers. This paper deals with the primary magnetic field analysis and basic winding calculations by an example of 54 slots and 20 poles PM synchronous generator. Modeling of the primary magnetic field distribution by the finite element method in software FEMM is described. Results from the analytic calculations and the finite element method are compared with experimental data of PM prototype generator study.