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SUMMARY This paper presents a novel type of flux-modulating synchronous machine (FMSM) in which permanent magnets (PMs) are embedded in the stator back-iron. The rotor has neither windings nor PMs. A prototype machine with an outer-rotor configuration was designed and manufactured to validate the operating principle of the FMSM. The characteristics in the motor mode of the prototype machine were also investigated with a vector control system. The results of the investigations show that, as in surface-mounted PM motors, the torque of the FMSM is predominantly generated by the PM flux and can be controlled using the armature current. [ABSTRACT FROM AUTHOR]

In this study we investigate a method for accurately calculating the characteristics of salient-pole synchronous machines assisted by permanent magnets. First, the operating principle of the machines is investigated by using both finite element analysis and a simple magnetic circuit. Then, a theoretical representation of the assist effect on the permanent magnets is derived based on the magnetic circuit. Finally, the measured and calculated results are compared in order to confirm the validity of the proposed calculation method. We show that the load characteristics of the proposed machine can be accurately estimated from the no-load and short-circuit characteristics of the conventional machine without permanent magnets, and the size and magnetization of the inserted permanent magnets. [ABSTRACT FROM AUTHOR]

SUMMARY The flux-modulating synchronous machine (FMSM) is a new type of multipole SM with nonoverlapping concentrated armature and field windings on the stator. This paper compares the output characteristics of two FMSMs through finite element analysis (FEA) and experiments. In both of the FMSMs, the attachment positions of the armature and field windings are swapped. To determine the reason for the discrepancies in their output characteristics, unsaturated inductances were calculated using a d- -q equivalent circuit. In addition, the calculated results of the inductances were confirmed through a visualization of the leakage fluxes using FEA. The results of the study show that the synchronous inductance can be reduced by attaching the armature winding to the air-gap side of the stator teeth and that the reduction leads to an increase in output power. [ABSTRACT FROM AUTHOR]

SUMMARY In designing solid-pole synchronous machines, it is important to take into account the surface eddy-current losses in the field pole cores. In this study, a solid-iron ring specimen is adopted as an approximate model of solid-pole surfaces in order to conduct a fundamental study of the surface losses. The influence of the minor hysteresis loops on the losses under dc-biased magnetization is investigated. The losses in the ring under dc-biased magnetization are measured and analyzed by finite element analysis (FEA). The losses computed by the FEA considering minor loops are nearly the same as those measured. In contrast, the eddy-current losses computed by FEA without considering minor loops are considerably inaccurate because the incremental permeability is overestimated and the skin depth is underestimated. It is important to consider hysteresis for the accurate calculation of the surface eddy-current losses under dc-biased magnetization. [ABSTRACT FROM AUTHOR]

In this paper, a new salient-pole synchronous generator (SG) termed the PMa-SG is presented. In the PMa-SG, permanent magnets (PMs) are placed between the pole shoes to reduce the magnetic saturation in the field poles. By using finite element analysis (FEA), the internal magnetic fields and basic characteristics of a 2.8-MVA PMa-SG are compared with those of a conventional SG of the same size, and the reduction effect of the magnetic saturation of the PMs is examined. The FEA simulations are also validated by experiments on a 2.0-kVA prototype machine. The PMs placed between the pole shoes reduce the magnetic saturation in the pole bodies and pole tips and effectively increase the terminal voltage and output power. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(4): 58-67, 2011; Published online in Wiley Online Library (). DOI 10.1002/eej.21132 [ABSTRACT FROM AUTHOR]

We propose a new method for analysis of the harmonic wave components of magnetic fields in rotating machinery. Using the magnetic permeability obtained by transient analysis of the nonlinear magnetic field, the harmonic wave components of the magnetic field are individually calculated in the spaces of both the rotor and stator subject to the boundary condition that the harmonic wave components obtained by the transient analysis are set on the sliding surface. Mode separation of the magnetic field will contribute to research on reducing harmful harmonic wave components for rotating machinery. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(2): 55–63, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20951 [ABSTRACT FROM AUTHOR]

In order to evaluate magnetic saturation under subtransient and transient states of a large-sized salient-pole synchronous machine, the currents and leakage inductances after sudden three-phase short circuits are analyzed by a two-dimensional nonlinear transient finite element method (FEM). The currents are calculated both by direct and indirect methods. The direct method uses the FEM and considers fluctuation of the magnetic saturation after the short circuit. The indirect method solves Park's differential equations without fluctuation. Results of the direct method agree well with measurements. When the preshort voltage is large, fluctuation of the leakage inductances after the short is large and it greatly affects values of the short-circuit currents. As the preshort voltage becomes large, the damper leakage inductances saturate at first, then the field leakage inductances, and finally the armature leakage inductances saturate. Although the indirect method considers saturation under the preshort condition, it gives inaccurate results and they are nearly the same as the results by the linear FEM. In general, it is thought that saturation of the leakage flux should be considered when subtransient conditions with large disturbance are analyzed. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(4): 46–55, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10240 [ABSTRACT FROM AUTHOR]