This article focuses on modeling of an Axial Flux Permanent Magnet Generator (AFPMG). The authors analyzed selected variants of disk generators, including coreless stator constructions and with iron core ones, also taking into account the Permanent Magnet (PM) arrangement in order to show the way to obtain the optimal machine characteristics based on analytical equations. In addition to the full model, which takes into account the higher harmonics of the magnetic field distribution, the paper presents a simplified mathematical model developed for generator operation cases such as standalone, connected to a 3-phase power grid and loaded with a diode rectifier. The analytical and finite-element method (FEM) calculations were performed as well as laboratory tests to confirm the correctness of presented model assumptions.

This paper presents analysis of 3-phase Axial Flux Coreless Generator with one stator with non-overlapping windings and two rotor discs with 28 Permanent Magnets on each. The author focuses on comparison of generator efficiency and Electromotive Force shape depending on shape and arrangement and volume of the Permanent Magnets using the field calculation. To show the impact of Permanent Magnets for work of AFPM Generator the author used simulation Program ANSYS Maxwell. Simulation results show the possibility of increasing the efficiency of this kind of machines exchanging only the Permanent Magnets while maintaining the economic aspect and taking into account the attractive force between the rotor discs.

This paper presents a model of 3-phase axial flux coreless generator with permanent magnets located on the rotor. Such design solutions are often carried out amateurishly and used in small domestic wind power plants. The premise priority of creating a mathematical model of the generator, presented in this article, was simplicity and reference to the classic solutions of electric machines. The interaction of higher harmonics of flux density distribution on the Electromotive Force (EMF) shape is considered. The analytical relationships of mathematical model are verified on the base of the laboratory tests.

Single-phase short-circuits are most often faults in electrical systems. The analysis of this damage type is taken for backup power supply systems, from small power synchronous generators. For these hybrid installations, there is a need for standard protection devices, such as fuses or miniature circuit breaker (MCB) analysis. Experimental research mentioned that a typical protective apparatus in low-voltage installations, working correctly during supplying from the grid, does not guarantee fast off-switching, while short-circuits occur during supplication from the backup generator set. The analysis of single-phase short-circuits is executed both for current waveform character (including sub-transient and transient states) and the carried energy, to show the problems with the fuses and MCB usage, to protect circuits in installations fed in a hybrid way (from the grid and synchronous generator set).

This paper presents an analysis of the short-circuit currents of a synchronous generator with a rated power of 16 kVA. For this purpose, the authors carried out measurements of real short-circuit currents during laboratory tests. Additionally, a simulation model of the generator was developed according to the individual machines data from the catalog and field calculations in ANSYS Maxwell software. Based on the mentioned research, the authors compared waveforms of the symmetrical short-circuit currents. In this paper, the last compared family of short-circuit current waveforms was obtained using analytic calculations. As the presented comparison shows, the assumed method of selecting short-circuit waveforms impacted their values. However, the difference in energy related to short-circuit currents did not influence on the selection of the short-circuit protections, especially at low values of steady-state short-circuit currents and short time constants characteristic for the generators, performing the functions of an alternative power supply. Regardless of the research method, the results presented in the article show that the selection of the short-circuit protections is complicated in case of hybrid electrical systems equipped with low power generators.

The active power losses are dependent on the flowing electric power value through overhead and cable lines. The current flow through the conductor causes negative phenomena to occur, such as released heat. The source of the current harmonics is the non-linear loads. Hence, the skin effect occurs, and the current carrying capacity of cables is reduced. This results in the increase in and uneven distribution of the temperature inside the conductor. This paper presents a comparison of the temperature distribution inside a power cable for an ideal 50 Hz sine wave and highly distorted current $(TH{D}_I=41\%)$. The calculated active power losses for the IEC 60287-1-1:2006+A1:2014 standard and the method described in the literature were used as a basis for further calculations. The obtained results revealed the problem of the uneven distribution of the conductor temperature. Considering the skin effect, increasing the temperature in the outer layers leads to severe damage and faster insulation aging. The abovementioned phenomenon is a decrease in the permissible load capacity of the conductor. The table given in the IEC 60364-5-52 standard summarizes the percentage contribution of the third harmonic to the current waveform. For percentages between 15% and 33%, the current carrying capacity is reduced by up to 86% of the full-load current rating. In addition, consideration of thermal conditions forces the use of cables with larger cross-sections. This leads to their non-optimal use and makes the investment more expensive from an economic point of view.