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This paper investigates the optimal arrangement of the coils in a wound-type interphase reactor to avoid the decreased inductance due to local saturation in the core when operated with high dc current. In theory, the direct currents and the related magnetomotive forces in the two ways of an interphase reactor are equal, and this compensation leads one to conclude that the global flux in the yokes is zero. However, the dc currents in the coils produce a significant leakage flux that flows locally in the core. If the coils are not suitably arranged and if the dc current is high, the leakage flux causes local saturation, a drop in the inductance, and noticeable circulation of a triple harmonic current through the reactor. Such a phenomenon is investigated by means of both a simplified field model and three-dimensional magnetostatic simulations. A number of criteria for the arrangement of the coils to improve operation are derived and applied to a real rectification system used in an electrolysis plant. Some in situ operational measurements of both the original and the improved interphase reactor are reported. [ABSTRACT FROM PUBLISHER]

Due to the high torque capability, axial flux (AF) permanent-magnet (PM) machines are an interesting solution for direct driven wind energy conversion systems and low-speed motors. However, the structure of such machines makes them sensitive to geometrical imperfections due to manufacturing process. This paper analyzes the effects that various types of geometrical imperfections produce in concentrated coil AF PM generators. In particular, a case study is presented, where the mechanical stresses, the resulting axial force, and the bending torques on the shaft, as well as the circulation current in the winding parallel paths, are calculated. The results obtained by means of an analytical approach are compared with those based on finite element method simulations and are validated by some experimental results on a prototype. [ABSTRACT FROM PUBLISHER]

An analytical method is presented to evaluate the field and global quantities for the operation and design analysis of axial flux permanent-magnet (PM) machines. The method, of general applicability, is based on the definition and superposition of suited field functions, able to accurately model the different singularities of the studied device: PM field distribution, effects of slotting, and radial end effects. Selected explorative FEM analyses are used in order to investigate the field functions shape and to help in identifying their structure and parameters. Then, the flux density distribution is obtained, as a function of the rotor position, taking into account some manufacture dissymmetry effects, such as air-gap offsets and PM rotor disk inclinations. This approach allows to analyze the effect of dissymmetry on the circulation of current among winding parallel paths in no-load operation. Moreover, by using the Maxwell stress tensor, the stress distribution is evaluated, as well as the resultant axial forces and the bending torques on the shaft due to the rotor disk tilts. Several FEM simulations show the soundness of the proposed method, which exhibits high accuracy and great evaluation speed. [ABSTRACT FROM PUBLISHER]

Some design and operation aspects of axial flux permanent magnet synchronous machines, wound with concentrated coils, are presented. Due to their high number of poles, compactness, and excellent waveform quality and efficiency, these machines show satisfactory operation at low speeds, both as direct drive generators and as motors. In this paper, after a general analysis of the model and design features of this kind of machine, the attention is focused on wind power generation: The main sizing equations are defined, and the most relevant figures of merit are examined by means of a suitable parametric analysis. Some experimental results obtained by testing a three-phase, 50-kW, and 70-rpm prototype are presented and discussed, validating the modeling theory and the design procedure. [ABSTRACT FROM AUTHOR]