The conducted noise signal induced by electromagnetic interference enters the device as a common mode noise and receives the mode conversion inside the device to become a noise signal that is a cause of malfunction. The quantitative evaluation of malfunctions requires the amount of mode conversion to understand noise signals. Therefore in this paper, we propose a method to obtain the mode conversion amount from the common mode noise to differential mode noise as the voltage attenuation characteristic by voltage excitation and potential difference observation. The validity of the proposed method was shown by comparison with the measurement results for the differential line using the conventional method and by comparing the conventional method with the proposed method by circuit simulation. In addition, by applying it to an operating board on which an IC is mounted and confirming its effectiveness.

This study investigates the characteristics of acetic acid decomposition on a negative DC corona discharge over water. The corona discharge is 4 mm away from the water surface. Furthermore, this study explores the mechanisms involved in the chemical reactions of active species during water treatment, using discharged plasma. During processing, oxygen or ozone is supplied to the reactor. The results of experiment and simulation show the same trend on time variation of acetic acid concentration. Therefore, the simulation model that considers the supply of ozone, hydrogen peroxide and O₃^- can confirm the change in acetic acid concentration. Our results indicate that negative ions such as O₃^- can be used for water treatment by DC corona discharge.

The non-radiative dielectric (NRD) waveguide, which has a structure with a dielectric line sandwiched between two metal plates, is known to have low loss and excellent non-radiative properties in the terahertz region. Nematic liquid crystals (NLCs) with good response and large dielectric anisotropy even in the terahertz wave region, have been attracting attention in recent years as one of the high-frequency materials. By replacing a part of the dielectric with a NLC, a NRD waveguide type terahertz variable phase shifter can be obtained. In this study, we use simulation to analyze the electric field distribution in the structure of the proposed NRD waveguide type phase shifter, and clarify the response characteristics with both simulation and experimental results. The response improvement of this device is also discussed.

A three-legged wound transformer core is composed of two inner cores and one outer core, and the interlaminar flux occurs between inner and outer cores in three-phase excitations. Past analyses of magnetic properties of three-legged wound transformer cores were based on the model of independent magnetic paths in the individual core, and did not factor the influence of interlaminar flux in the calculations. This paper shows experimental results of interlaminar flux between cores and iron loss increase caused by that. Results show that the interlaminar flux between the inner and outer core increases the local iron loss in the boundary region of the inner and outer core.

The purpose of this study is improvement of metal identification performance with step response. Feature values are maximum derivative current and its reaching time, these values depend on lift-off in the range of 0.5-1.5 mm. As a result of metal identifications, decision tree is the fastest and highest accuracy in 4 machine learning models. When increasing training samples, calculation time of all models are increasing, and accuracies are saturated 100 samples. When comparing between data whose lift-off is from 0.5 to 1.5 mm and data that fixed lift-off, classification accuracy in data fixed lift-off is improve than one in data not fixed lift-off.

We assessed the time dependence of the difference between living and dead yeast suspensions, in terms of the amplitudes and phase angles of their harmonics, when an alternating current (AC) voltage was applied to a yeast suspension. The measurements were repeatable and it was possible to accurately and quickly determine yeast status (living or dead) even within 1 s by reference to the phase angles of the 3rd harmonic. We found that measuring the phase angle of a dead yeast suspension in the system in advance permits us to distinguish between living and dead yeast without the need to calculate their relation to fundamental components such as the amplitude. This method based on the phase angles of harmonics is a powerful and convenient technique for quickly determining the status of yeast. These nonlinear responses change due to the presence of yeast itself and the collection of data on them including phase angles helps us to understand the electrical properties of cells.

The direct current integrated charge method (Q(t) method) is a useful method to understand dielectric properties of insulating materials with a simple treatment. As total currents flowing through the insulating material are integrated by a capacitor, Q(t) data include various information about the material in them. To understand the Q(t) data, especially from the view point of electric charge behaviors, a parameter “charge ratio Q(t_m)/Q(0)” which is the ratio of the initial charge amount Q(0)=CV and the Q(t) after time t_m is introduced. An algorithm for classifying the electrode charge amount Q(0), the space charge accumulation amount Q_spac(t), and the leakage current charge amount Q_leak(t) using charge ratio is proposed and evaluated.

Decomposition gases due to partial discharge (PD) conditions in an oil-impregnated paper insulation system with an oil gap were experimentally investigated. Sheets of oil-impregnated paper were sandwiched between parallel plane electrodes. An oil gap was made up by overlapping sheets of oil-impregnated paper with a hole. Insulating oil was taken from the oil gap after PDs were generated in the short or long duration, and the dissolved gas analysis was conducted. As a result, it was revealed that there was a difference in the ratio of each gas volume to the total volume of gases. The ratios of H₂ and C₂H₂ were higher than those of other gases in short duration cases, while the ratios of H₂, CH₄ and C₂H₆ were higher than those of other gases in long duration cases. PDs occurred through the insulating oil in the short duration cases. On the other hand, PDs occurred in gases in the long duration cases. The result suggests that the difference of main decomposition gases in two cases is due to the difference of the place where PDs occurred.

A new phenomenon, called “local carbonization” inside a stator core was detected as a unique precursor to fragility of the insulation sheets of inverter-fed motors, and the conditions for generation of this carbonization were investigated. A separated stator of a product inverter-fed motor was manufactured, and an evaluation system for simulating a steep surge voltage was constructed. Electrically and mechanically, the results of a parameter survey of insulation system were used to compare the constructed separated stator and element model, and the comparison revealed a correlation between carbonization of the product separated stator and element model. From the consideration of carbonization mechanism, leakage current was revealed to be the dominant design factor. Through quantifying their threshold of carbonization occurrence, insulation system to prevent the carbonization in steeper inverter surge was developed by parameter survey using element model and validation test by separated stator.