# Masato EnokizonoOita University, Vector Magnetic Characteristic Technical Laboratory

Masato Enokizono

Emeritus Prof. Dr. of Oita University. President of Vector-Magnetic Characteristic Technical Laboratory

## About

586

Publications

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Introduction

Head of Vector Mqgnetic Characteristic Technical Laboratory

**Skills and Expertise**

Additional affiliations

April 2013 - present

February 1980 - March 2013

## Publications

Publications (586)

In this paper, a stator core shape design method is proposed for an improvement in the power density of a small surface-mounted permanent magnet (SPM) motor. In order to improve the power density of a motor, it is necessary to increase its torque or reduce its weight. However, when a stator core shape is miniaturized to reduce the weight of the mot...

This paper presents the newly proposed heating method names as “Secondary Current Heating Method” to reduce the iron loss on laminated electrical steel sheet cores for high efficiency electrical motors. It is well known that the magnetic properties of electrical steel sheets, which are used for electrical motor cores, are deteriorated by the residu...

We prove that the signature of the Milnor fiber of smoothings of a $2$-dimensional isolated complete intersection singularity does not exceed the negative number determined by the geometric genus, the embedding dimension and the number of irreducible components of the exceptional set of the minimal resolution, which implies Durfee's weak conjecture...

The Horikawa index and the local signature are introduced for relatively minimal fibered surfaces whose general fiber is a non-hyperelliptic curve of genus $4$ with unique trigonal structure.

In order to design a high-efficiency motor, the iron loss that is generated in the motor should be reduced. The iron loss of the motor is generated in a stator core that is produced with an electrical steel sheet. The iron loss characteristics of the stator core and the electrical steel sheet are agreed due to a building factor. To evaluate the iro...

The iron loss of industrial motors increases by residual stress during manufacturing processes. It is very important to make clear the distribution of the residual stress in the motor cores to reduce the iron loss in the motors. Barkhausen signals which occur on electrical steel sheets can be used for the evaluation of the residual stress because t...

Recently, the application areas for electric motors have been expanding. For instance, electric motors are used in new technologies such as rovers, drones, cars, and robots. The motor used in such machinery should be small, high-powered, highly-efficient, and high-speed. In such motors, loss at high-speed rotation must be especially minimal. Eddy-c...

We are developing a low-loss stator core for high-speed and small-size motors using an ultrathin electrical steel sheet. This stator core for a high-speed motor was produced using a 0.08mm-thick ultrathin electrical steel sheet. Additionally, in order to evaluate the iron loss of the high-speed motor stator core, we constructed a high-speed buildin...

In order to develop low loss and low acoustic noise motor with high speed rotation, it is important to measure vector magnetic characteristics and two-dimensional magnetostriction of a non-oriented electrical steel sheet. The iron loss of motor core material increases depending on frequency. A ultra-thin non-oriented electrical steel sheet is devel...

This paper presents influence of induction heating treatment with a cylindrical magnetic flux concentration plate on vector magnetic properties of a non-oriented electrical steel sheet. The non-oriented electrical steel sheet is heated by using induction heating method. The vector magnetic properties of the non-oriented electrical steel sheet under...

This paper presents measured results of the two-dimensional vector magnetic properties in non-electrical steel sheets for different thickness under high frequency excitation conditions. Mars Orbiter require small size high power motor. In order to obtain its, it is necessary to rotate a motor under high-speed. However, motor efficiency reduces unde...

This paper presents measured results of the two-dimensional vector magnetic characteristics of ultra-thin electrical steel sheets for high efficiency high speed motors. Generally, Non-oriented electrical steel sheets with from 0.2 mm to 0.5 mm of thickness are used for motor cores. However, their thicknesses are not appropriate to use for cores of...

This paper presents the newly proposed heating method names as "Secondary Current Heating Method" to reduce the iron loss on laminated electrical steel sheet cores for high efficiency electrical motors. It is well known that the magnetic properties of electrical steel sheets, which are used for electrical motor cores, are deteriorated by the residu...

The magnetic properties of electrical steel sheets, which are used as core materials in numerous electric-powered machines, tend to deteriorate due to residual stress and external loads during manufacturing processes. Previously, we reported our measurement results for the residual stress distribution in a motor core and clarified that sheer stress...

In this paper, we propose a stator shape design method for improving power density in a small PM motor. In order to calculate iron loss correctly, we analyze a motor by using two-dimensional FEM in which E & S model is introduced. Moreover, external circuit equations are solved coupled with equations in electromagnetic field by FEM to calculate cop...

We give a slope equality for fibered surfaces whose general fiber is a smooth plane curve.

We prove a "strong" Durfee-type inequality for isolated hypersurface surface singularities, which implies Durfee's strong conjecture for such singularities with non-negative topological Euler number of the exceptional set of the minimal resolution.

We give examples of local signatures, completely different from the usual ones, for general fibrations of genus $2$ and genus $3$.

This paper presents local vector magnetic properties in a three-phase induction-motor model core under sinusoidal and PWM excitation. The distributions of the vector magnetic properties were measured using a small sized vector magnetic sensor (V-H sensor). The results show a clear influence of the magnetic anisotropy due to rolling, although the co...

This paper presents our proposed frequency sweeping excitation and spectrogram method (FSES method) by a magnetic sensor for non-destructive testing of hardened low carbon steels. This method can evaluate the magnetic properties of low carbon steels which were changed after induction heating treatment. It was examined by our proposed method that th...

To prevent injury from metal degradation of structural metallic material such as stainless steel, we have previously proposed fatigue evaluation methods such as the remnant magnetization method and the inductance method. These fatigue evaluation methods showed a positive correlation between the magnetic sensor output signal and the amount of the pl...

It is well known that the magnetic properties of a stator core in a rotating machine such as an induction motor are influenced by residual stress and external force. Residual stress is generated during manufacturing processes such as punch, laminate, and shrink fit processes. Magnetic properties such as iron loss of the stator core increases dramat...

The Barkhausen signal was used for the nondestructive evaluation methods in order to evaluate residual stress levels in ferromagnetic materials. However, it cannot be said that this technique has been established completely because the evaluation is usually not done under controlled magnetic flux conditions. When the magnetic field is applied into...

We consider the improvement of the stator structure of self-propelled rotary actuator whose rotational axis is parallel to the exciting magnetic field. The stator of the actuator is constructed from the grain-oriented electrical steel sheet. The relation between the rolling direction of the steel sheet and the direction of the exciting magnetic fie...

This paper describes about the core loss (magnetic power loss, iron loss) reduction method for upgrading high efficiency motor. It is difficult to achieve the core loss reduction of motor by using conventional technique. Therefore we proposed the vector magnetic characteristic technology which is constructed magnetic characteristic analytical metho...

The Barkhausen signal was used for the non-destructive evaluation methods in order to evaluate residual stress levels in ferromagnetic materials. However, it cannot be said that this technique has been established completely because the evaluation is usually not done under controlled magnetic flux conditions. When the magnetic field is applied into...

This paper presents our proposed frequency sweeping excitation and spectrogram method (FSES method) by a magnetic sensor for non-destructive testing of hardened low carbon steels. This method can evaluate the magnetic properties of low carbon steels which were changed after induction heating treatment. It was examined by our proposed method that th...

This paper describes about the core loss (magnetic power loss, iron loss) reduction method for upgrading high efficiency motor. It is difficult to achieve the core loss reduction of motor by using conventional technique. Therefore we proposed the vector magnetic characteristic technology which is constructed magnetic characteristic analytical metho...

We establish the slope equality and give an upper bound of the slope for finite cyclic covering fibrations of an elliptic surface including bielliptic fibrations of genus greater than 5. We also give an upper bound of the slope for triple cyclic covering fibrations of a ruled surface and hyperelliptic fibrations, which provides a new proof of Xiao'...

This paper presents the effect of stress-relief annealing on magnetic properties using an induced current heat-ing(ICH) method in order to reduce the residual stress in the motor cores. The magnetic properties of a motor core annealed using the ICH method were first compared with those of a core annealed using a conventional electric furnace. When...

To prevent a serious accident by the metal degradation of a structure made of iron-based structural materials, we have already proposed some fatigue evaluation methods for various iron-based structural materials. One of these is a residual magnetization method that uses a thin-film flux-gate magnetic sensor. This method is called the perpendicular...

This paper presents two-dimensional magnetostriction analysis using a numerical method of two-dimensional magnetostriction (E&S-W model) on magnetic core in induction motor. In order to reduce vibration and acoustic noise of the electrical machines, it is necessary to evaluate the magnetostriction of the magnetic core. The two-dimensional magnetost...

This paper presents vector magnetic characteristic analysis by using the complex E&S modelling taking account of stress effect. According to the past researches, we have evaluated the magnetic field strength H vector under controlled stresses and sinusoidal magnetic flux density waveforms. However, it is impossible to control the magnetic flux dens...

Highly efficient hybrid type magnetic bearing is proposed in this paper. It is intended to apply the proposed magnetic bearing to ultra low temperature fluid pump. Traditional low temperature pump is supported by a ceramic ball bearing which is damaged by the low temperature liquid. Non-contact support is highly requested. However, the standard ele...

Electrical steel sheet that is used as a core in electrical machines deteriorates due to residual stress and external stress. The magnetic properties and stress need to be clarified in order to effectively utilize electrical steel sheet in electrical machines. We have measured the residual stress distribution in a motor core using an X-ray stress m...

The magnetic properties of electrical steel sheet used in motor cores are influenced by mechanical stress due to the inverse effect of the magnetostriction. Therefore, it is necessary to measure the magnetostriction of the electrical steel sheet in order to clarify the relationships between the stress and magnetic properties. The present paper inve...

In order to improve efficiency of electric equipment, it is necessary to use a high-quality magnetic material and to fully utilize the magnetic properties without deterioration. It is known that the iron loss of the amorphous material is about one-third of that of the grain oriented electrical steel sheet. However, the amorphous material has a larg...

Past magnetic property measuring methods such as the single sheet test (SST) and the Epstein method cannot quantitatively evaluate magnetic properties of an actual stator core that shows complex shape. Therefore, we are researching the stator winding excitation method as a new method to evaluate magnetic properties (iron loss and maximum magnetic f...

There is rotational iron loss under the V-junction in the yoke in an actual transformer because not only alternating magnetic field but also rotational and elliptical magnetic field are generated. The rotational iron loss can not be grasped in the standard magnetic measurements because it is assumed that the vectors of magnetic flux density B and m...

This paper presents two-dimensional magnetostriction analysis using a numerical method of two-dimensional magnetostriction (E&S-W model) on transformer model core. In order to reduce vibration and acoustic noise of transformer, it is necessary to evaluate the magnetostriction on the magnetic core. The two-dimensional magnetostriction on electrical...

We give an algorithm to classify singular fibers of finite cyclic covering
fibrations of a ruled surface by using singularity diagrams. As a first
application, we classify all fibers of 3-cyclic covering fibrations of genus 4
of a ruled surface and show that the signature of a complex surface with this
fibration is non-positive by computing the loc...

This paper presents two-dimensional magnetostriction of electrical steel sheet under vector magnetic characteristic. In conventional measurement method using Single Sheet Tester, the magnetic flux density, the magnetic field strength, and the magnetostriction have been measured in one direction. However, an angle between the magnetic flux density v...

We study slopes of finite cyclic covering fibrations of a fibered surface. We
give a best possible lower bound of the slope of these fibrations. We also give
the slope equality of finite cyclic covering fibrations of a ruled surface and
observe the local concentration of the global signature of these surfaces on a
finite number of fiber germs. We a...

We have reported the measured results for the magnetic properties of a non-oriented electrical steel sheet under various magnetic flux and stress conditions and proposed a new vector magnetic characteristic analysis technique to consider the stress effect on the motor core. In this paper, the stress effect on the magnetic flux density vector, magne...

In this paper, we consider the improvement of the stator structure of the self-propelled rotary actuator, whose rotational axis is parallel to the exciting magnetic field. The stator of the actuator is constructed from the grain-oriented electrical steel sheet. The relation between the rolling direction of the steel sheet and the direction of the e...

In recent years, iron-based materials such as steel have been utilized in many structural components. We have already proposed the fatigue evaluation method for steel by measuring an inductance of a pancake-type coil using an LCR meter. In the case of low carbon steel, pulsating tension fatigue was evaluated using the inductance method. In the case...

Magnetic analysis method considering vector magnetic characteristic and two-dimensional magnetostriction of electrical steel sheet is suggested and distribution of the two-dimensional magnetostriction on transformer model core is clear by the analytical method. In particularly, the large magnetostriction occurs at T joint part due to occurrence of...

We have been reported measured results for magnetic properties of a non-oriented electrical steel sheet under various magnetic flux and stress conditions and a new vector magnetic characteristic analysis technique in order to consider the stress effect on magnetic properties in the motor core. Next, we try to control the vector magnetic properties...

This paper presents two-dimensional magnetostriction analysis using a numerical modeling method of two-dimensional magnetostriction (E&S-W model) on magnetic core in induction motor. In order to reduce vibration and acoustic noise of the induction motor, it is necessary to evaluate the magnetostriction on the magnetic core. The Two-dimensional magn...

It is assumed that vectors of magnetic flux density B (B-vector) and magnetic field strength H (H-vector) are parallel in the standard magnetic measurement; however, they are not parallel in actual electrical steel sheets. We have proposed the 2-D vector magnetic measurement technique which can measure the B-vector and H-vector that are in differen...

It is well known that magnetic properties, such as iron loss of a stator core in a rotating machine like an induction motor, are strongly influenced by residual stress caused by manufacturing processes. In particular, both the residual stress that was generated by the punching and the laminating process greatly influence the iron loss. However, it...

Experts now know that past iron loss measuring methods cannot quantitatively evaluate iron loss in an actual stator core with a complex shape. As such, we are researching a new method to measure the iron loss and magnetic properties of an actual stator core. We have already proposed a stator winding excitation method (SWEM), which can directly eval...

This paper presents a numerical modeling method of two-dimensional magnetostrictions on a non-oriented electrical steel sheet and a grain-oriented electrical steel sheet under alternating and rotating magnetic flux conditions. Non-sinusoidal magnetic flux occurs in a core of electrical machines due to excitation conditions and magnetic anisotropy....

Magnetic gears are a force transmitter consisting of permanent magnets. The mechanical input can be transmitted to an output shaft without contact by magnetic forces. The transmission property of the magnetic gears is usually better than that of mechanical gears, because it is free from transmission loss, mechanical friction, lubrication oil, dust,...

Magnetic properties of electrical steel sheet which is used motor cores are influenced due to mechanical stress. Therefore, it is necessary to know the magnetic properties under tensile, compressive and shear stress conditions in order to utilize the electrical steel sheet effectively. This paper presents the influence of the principal stress on ve...

In order to clarify the iron loss distribution in iron core of electric machines, the magnetic field analysis considering 2-D vector magnetic properties is effective. Several kinds of modeling of 2-D vector magnetic properties are proposed, the complex E&S modeling is most simplified and is useful to optimal design of electric machines. 2-D vector...

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 d...

This paper presents three-dimensional boundary element analysis for coupled magnetic field and moving problem. The method is applied to improve transmission characteristics of a magnetic gear and the usefulness is demonstrated. The gear has two movers consisting of permanent magnets and they rotate with different velocity. The double gap moving pro...

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 casti...

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...

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...

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 MCS...

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...

Magnetizations and optical Faraday effects have been intensitvely studied in transparent glasses of almost all Lanthanide elements with 20mol % in pulsed magnetic fields up to 30T in the temperature range between 1.8K- RT. The internal effective fields were investigated by observing Verdet constants as a function of applied fields and as a function...

In order to reduce acoustic noises and vibrations of electrical machines caused by magnetostriction, it is necessary to make clear the distribution of magnetostriction on magnetic core. The distribution of magnetostriction has been visualized by measured two-dimensional magnetostriction of electrical steel sheet and vector magnetic characteristics...

The magnetic properties of electrical steel sheet deteriorates due to residual stress, which occurs during the manufacturing process. Therefore, it is important to know the relationship between the magnetic property and the residual stress in order to utilize electrical steel sheets effectively. This paper presents the effect of residual stress on...

Magnetic properties of nonoriented electrical steel sheets are influenced by mechanical stress because they exhibit the phenomenon of magnetostriction. Therefore, it is necessary to clarify the relationship between magnetic properties and magnetostriction under mechanical stress. This paper presents the results of measurements of the vector magneti...

To reduce power loss of transformers further from now on and to raise efficiency, we have measured magnetic property distributions in a three-phase tripod V-connection transformer model core. For the measurement, we have developed a localized vector magnetic property measurement system consisting of a three-axis positioning system, a vector magneti...

In electrical equipment, such as transformers and motors, rotating magnetic fluxes occur at T-joint parts and back yoke parts. It is therefore necessary to understand the magnetic properties and magnetostrictions under several rotating flux conditions. This paper presents measured vector magnetic properties including 2-D magnetostriction of a nonor...

This paper presents iron loss distributions in divided-stator model cores calculated with the finite-element method considering vector magnetic properties. The magnetic anisotropy and rotational iron loss were considered using the dynamic E&S modeling. In this paper, we discuss the differences of the calculated results depending on the direction of...

In this paper, the improvement of magnetic properties of oriented electrical steel sheets has been examined by using a laser irradiation system. It is well known that magnetic properties in the rolling direction of oriented electrical steel sheets can be improved by applying laser stress into the surface of the steel sheets. However, the laser stre...

Recently, progress of intelligent materials has played a big role in the development of science and technology. We have tried to develop ferromagnetic shape memory alloys to expand application range of the nonmagnetic shape memory alloys, which are typical intelligent material. However, we have not yet obtained a sufficient result, because the magn...

In recent years, the precise magnetic properties of electrical steel sheet are needed to develop high efficiency electromagnetic devices. An IEC standard single sheet tester is often used for the magnetic property measurement, especially for commercial transactions. But it is not accurate, so is not proper for the material evaluation based on its p...

Magnetic properties of motor cores are deteriorated due to residual stress occurred during manufacturing process. Therefore, it is necessary to reduce the residual stress in motor cores through stress-relied annealing. As a conventional method, electric furnaces have been used to anneal motor cores. However it takes a long annealing time and requir...

Vector magnetic properties and two-dimensional magnetostrictions of electrical steel sheets under alternating and rotating magnetic flux conditions were measured. Based on the measured database, magnetic characteristic analyses of motor and transformer model cores have been carried out and distributions of two-dimensional magnetostriction have been...

A study is carried out based on the evaluation of IEC-standard. Two measurement results on N.O. magnetic steel sheets, one from S-SST (Stress load type single sheet tester developed in our research laboratory), another is from SST based on the IEC standard regulation, are compared and discussed. As a result of the measurements, both magnetization c...

This paper presents measured vector magnetic properties and two-dimensional magnetostriction of a non-oriented electrical steel sheet (including a 6.5% SiFe sheet), a grain-oriented electrical steel sheet, an Fe-based amorphous sheet, and a permendur sheet. These electrical steel sheets have been widely used as a core material of electrical equipme...

This paper presents a modeling of vector magnetic properties considering residual stress effects in electrical steel sheets. Because the practical phenomenon is too complicated, complex variable expressions are applied to the modeling used in the characteristic analysis with the FEM. We call this stress-complex-E&S modeling. The validity of the dev...

In this paper influence of uniaxial stress loading on local changes of magnetic properties in a non-oriented silicon steel was examined. The measurements were carried out for different direction of loading force in respect to the rolling direction of the steel. Impact of the relationship between the rolling and the loading direction on evaluation o...

It is needed to know magnetic properties under various stress and magnetic flux conditions in order to utilize electrical steel sheets effectively. In this paper, we examine a measurement method of the vector magnetic properties of a non-oriented electrical steel sheet under stress conditions. At first, an evaluation method of the stress is examine...

A magnetic gear can transmit torque and motion without any mechanical contact, and also has wide applications in various systems where increase/decrease in speed has a vital role, but high reduction gear has not been proposed yet. In the mechanism, eddy currents are induced in the stator gear teeth. In this paper, the stator gear for high-speed whi...

This paper presents a moving-magnet type linear synchronous motor designed by using magnetic-flux concentration-type permanent magnet arrangement. The arrangement of permanent magnets in the mover structure is optimized with the three-dimensional finite element method in order to improve thrust characteristics. The calculated results are verified i...

In this paper, vector magnetic properties measurement and magnetic characteristics analysis of a non-oriented electrical steel sheet under high magnetic flux is presented. At first, the vector magnetic property of the non-oriented electrical steel sheet under the high magnetic flux condition is measured. Next relationships between the magnetic flux...

The Fifteenth Biennial IEEE Conference on Electromagnetic Field Computation (CEFC 2012) was held in Oita, Japan, on November 11-14, 2012. The statistics for CEFC 2012 are as follows: the registered attendance was 347 participants and 28 countries were represented at the Conference. There was an appreciable number of participants attending from Kore...

In this study, we conducted a detailed investigation of iron loss distribution using a thermographic camera system. Such measurements are important because the stator in an electric motor consists of electrical steel sheets and reducing their iron loss is an important factor in efficiency. Because iron loss is ultimately converted into heat, it can...

The measurements of the coercive force (Hc) of magnets are very difficult to determine as a function of the true effective fields in samples with arbitrary shapes. In this study, we tried to obtain the exact coercive force, M-H curve in high and high pulsed magnetic fields up to 20T by using a double-core pick-up. The values of Hc were found over-e...

Permanent magnets are widely used in many applications. A fast and
reliable system for online evaluation of permanent magnets is required
for their quality assurance. Therefore, a new measurement system has
been developed to measure the spatial distribution of the vector
magnetic field. The system consists of a complex Hall transducer, an
analog mu...

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 elect...