Papers by Author: Masato Enokizono

Abstract: This paper presents torque characteristic analysis of synchronous induction motors called “IM/PM hybrid motors” by using the two-dimensional finite element method taking terminal voltage into account. The slip characteristics are analyzed by using multi-meshes corresponding to each rotor position, because the transient numerical analysis is quite difficult due to slip even two-dimensional analysis. There are many researches on IM/PM hybrid motors, however the torque characteristics when they are operating as an induction motor have not yet examined sufficiently. In this paper, we tried to explore how to improve the torque characteristics even operating as an induction motor by incorporating the embedded permanent magnets. The results show that the arrangement of the permanent magnets is very important to improve whole torque characteristics.

Abstract: In this paper we will discuss about the development of IE4 level motor proposed by IEC, which is new target for international efficiencies. Efficiency classes IE1-IE4 are defined in international standard IEC 60034-30. The draft version of IEC 60034-31 defines the new class IE4. The IE-codes replaces the former voluntary Eff classification of electric motors as shown in Table 1. The Eff classes are based on a voluntary agreement between the EU and the CEMEP in 1998.Table 1 Minimum energy performance standards for electric motors.

Abstract: This paper presents vibration characteristics of a hybrid magnetic suspension model combining functions of a magnetic spring and a magnetic damper. Dynamic simulations considering the moving equation are performed with the step-by-step method based on the time-domain three-dimensional axisymmetric finite element method. The results demonstrate that the proposed hybrid model is effective to improve the performance to attenuate vibrations.

Abstract: This paper presents a magnetic coupling for a large-sized mixer, which is separated by a vessel wall. In order to improve the transmission-torque, the magnetic material attached magnetic-flux concentrated surface permanent magnet (MCSPM) arrangement is applied to the magnetic coupling and the construction is optimized. The results show that the MCSPM arrangement is very effective to improve the air-gap magnetic flux density and the transmission torque even quantity of very few permanent magnets.

Abstract: This paper presents results of magnetic characteristic analysis of a three-phase three-leg transformer model core. In the analysis, the finite element method considering vector magnetic properties expressed by the integration-type E&S modelling is used. In this research, in order to reduce total iron loss, local vector magnetic properties for some different T-jointed models are compared in detail. Distributions of maximum flux density, maximum field strength, axis ratio and iron loss depending on the T-jointed position are clarified.

Abstract: An NDE measurement for internal defects of metal casting products is presented. The internal defects are often made in the manufacturing process of metal casting. From the view point of non-destructive evaluation (NDE), it is very difficult to make artificial defects that simulate actual internal defects. Therefore, we prepared a lot of metal casting samples that may include defects, and investigated the relation between the defect dimensions and the spectrogram that were generated by Multi-Frequency Excitation and Spectrogram Method (MFES).

Abstract: In general, the magnetic properties of electrical steel sheets are strongly influenced by mechanical stress. We have reported the measurement results of vector magnetic properties of a non-oriented electrical steel sheet under stress conditions. From these results, it is possible to control the vector magnetic property by applying local mechanical stress. Therefore, we next focus on an induction heating technique that applies mechanical stress in a non-oriented electrical steel sheet. It is very important to control the eddy current distribution inside the non-oriented electrical steel sheet. This paper presents a magnetic flux concentration plate structure to control the eddy current in steel sheets by using an induction heating technique. The magnetic flux concentration plate structure is investigated in a three-dimensional magnetic field analysis by the finite element method.

Abstract: Recently, progress of the intelligent materials plays a big role in development of science and technology. We have ever tried to develop ferromagnetic shape memory alloys to expand application range of the common non-magnetic shape memory alloys, which are typical intelligent material. However the saturation magnetization and the shape memory effect were in a relation of trade-off, so we couldn’t get a good result. In this research, we tried to develop ferromagnetic shape-memory alloys as a composite material by using the single-roll melt spinning technique. They are bilayer ribbons, which have both shape memory layer and magnetic layer.

Abstract: To obtain the basic data to manufacture the highly effective rotating machine, the axial iron loss distribution of an actual stator core of the complex structure was evaluated by using the small excitation inner core. The laminated thickness of this small excitation inner core is approximately 1/6 of the thickness of the stator core. Therefore, the circumferential iron loss distribution of the stator core and the axial iron loss distribution of a stator core can be measured by using this small excitation inner core. Then, to compare the difference of the axial iron loss distribution in the stator core, we investigated the axial iron loss distribution in the actual stator core after two manufacturing processes, the laminating process and the shrink fitting process. The iron losses were measured in three places (the edge, the quarter part, and the center) of two stator cores. As a result of our investigation, the axial iron loss distribution in the actual stator core clearly changed. This paper reports on the axial iron loss distribution in two manufacturing processes in two actual stator cores measured by using the small excitation inner core.

Abstract: In this paper, we present a frequency sweeping excitation and spectrogram method (FSES method) for non-destructive testing of hardened carbon steels. The FSES method can evaluate the electromagnetic properties in materials which were changed after induction heating. Therefore, it’s possible to evaluate the hardening conditions using the FSES method. We applied our method to the practical car seat parts to use in actual products. The surface of the hardening sample is deformation by the induction heating. We show the method that can evaluate the hardening conditions without being influenced by the surface deformation.