For power equipment, defects in the insulation parts cause partial discharge, which leads to dielectric breakdown. Since dielectric breakdown can cause serious problems, measurement of partial discharge in actual equipment is important. However, it is difficult to identify partial discharge signals overlapped with noise signals using conventional techniques. Therefore, in this paper, we developed a new partial discharge detection method that can identify partial discharge signals and noise signals by analyzing waveform and phase distribution.

In this paper, discharge characteristics of the creepage surface on multi-layer printed circuit boards are investigated to identify the location where discharge occurs. Arc discharge is initiated by the corner of the surface layer electrode in spite of larger distance to the opposite electrode as compared with the electrode edge with straight line. This is attributed to the fact that electric field concentration originated from the decrease in curvature radius of the electrode edge is dominant rather than the increase in the distance between the electrodes at the corner of the electrode. In addition, novel insulation structures in which electric field intensity is reduced with the layout modification of surface and inner layer electrodes are proposed, which is specific to multi-layer printed circuit boards. The proposed structures enable high dielectric strength without increasing creepage distance.

Orthogonal-core-type variable inductors with permanent magnets can increase or decrease the line voltage without power capacitors in electric power systems. In this paper, 3 kVA orthogonal-core-type variable inductors with permanent magnets are designed based on reluctance network analysis (RNA), and verification tests are carried out. The results demonstrate that the prototypes perform as intended. Furthermore, to improve the calculation accuracy, the RNA model combined with an assumed flux path (AFP) method is proposed. The proposed method achieves a significant improvement in calculation accuracy without increasing calculation time.

We report a novel method for forming an oblate FRC through a modified single spheromak formation by a single flux-core coil with toroidal and poloidal coil windings. We have observed that by applying an external magnetic field that pulls the plasma during its formation, an initially formed spheromak-like plasma linked to a flux core coil splits into a spheromak and an oblate FRC.