Hiroyuki Sugawara

Vacuum Circuit Breaker Electrode Generating Multi-Pole Axial Magnetic Field and its Interruption Ability

Because the phase of the eddy currents in an electrode lags that of the main interruption current, a rather strong axial magnetic field remains at current zero in the space between a pair of electrodes when an interruption current is large. The authors analyzed the magnetic field on a circular conductor which was centered in a coil to stimulate an axial magnetic field type electrode. Because the authors found it difficult to eliminate the residual magnetic field from an electrode, they developed a new type electrode structure which does not generate a residual magnetic field at the center of an axis. An experimental vacuum interrupter equipped with this kind of electrode performed very well at testing voltages from 7.2 kV to 72 kV. Hitachi has applied this new type electrode in the development of a 7.2 kV 63 kA vacuum circuit breaker.

Development and Field Application of Metallic Return Protecting Breaker for HVDC Transmission

This paper describes the system requirements, circuit and component selections, development and field tests on a metallic return protecting breaker for an HVDC transmission system. Self oscillation phenomenon, generated in the course of DC current interruption by an air blast circuit breaker, is utilized to force the current to zero. Also discussed is outlook for development of an HVDC main line circuit breaker.

Development of a pulsed power supply for a large‐bore copper vapor laser

A pulsed power supply has been developed for exciting a copper vapor laser with a bore diameter of 80 mm and a discharge length of 2890 mm. The pulsed power supply has two thyratrons, an LC‐inversion circuit and a two‐staged magnetic pulse compression circuit. An efficiency of 82% has been obtained which is defined as the ratio of energy stored in the storage capacitor to the output energy of the magnetic pulse compression circuit, with a voltage greater than 40 kV, averaged output power of 24 kW, and voltage rise time of 70 ns. The pulsed power supply was successfully operated for more than 2000 h and an optical output power of 272 W was obtained.

A spacing sensor for magnetic disk systems

A sensor based on Frustrated Total Reflection (FTR) for measuring spacing between magnetic disks and sliders has been developed. Theoretical evaluation shows that when polarization and incident angle are properly chosen, this sensor should have twice the measurement range and at least three times the resolution of traditional methods of spacing measurement which use interference. The measurement range of the FTR sensor can be optimized for typical disk-slider spacings (<100 nm) easily, by changing the incident angle of the light. To evaluate its operation, the sensor was fabricated on the side of a glass slider by a lithography technique and spacing was measured. Taking the 20 nm offset caused by the beveled edge of the slider into account, measurement error was less than 1 nm for P polarized light and 10 nm for S polarized light. This sensor could potentially measure spacing between real magnetic disks and ceramic sliders,.

20-kW fast-axial-flow CO 2 laser with high-frequency turboblowers

A 20-kW fast-axial-flow CO2 laser has been realized by using high-frequency turboblowers developed especially for laser operation. Each of the two high-frequency turboblowers utilized in the equipment has a revolution of 8,800 rpm, a gas flow rate of 8.4 m3/s, and an adiabatic head of 4,000 kgf·m/kg. The equipment has six discharge-tubes connected optically in series, and each is 134 mm in diameter, and 1,000 mm in length. Stable glow discharge is established in the large-volume region without any preionization. The laser output power of 20 kW is extracted from an unstable resonator. The output beam through a zinc-selenide window has a diameter of 90 mn.

Effective refractive index method for frustrated total reflection: application to measurement of flying height

In order to measure the spacing between an actual magnetic disk and a slider, we developed a flying height sensor based on frustrated total reflection (FTR). When optically measuring the flying height of a slider, the phase shift on reflection at the magnetic disk is a significant problem. In this paper, we describe the theoretical treatment of the problem, introduce the modified effective refractive index method, and measure the effective refractive index of an actual magnetic disk. The flying height on a magnetic disk was also measured using the obtained effective refractive index. The result was compared with flying height measurements measured by the traditional interference method. They agreed with each other, with an error of less than 2.5 nm.

Flying height measurement using frustrated total reflection: determination of the reflectivities by the least-squares method

A new method for determining reflectivities in flying height measurement of a slider using frustrated total reflection (FTR) sensor is evaluated. The method is based on the fact that the reflectivity of FTR has different dependence on flying height for P-polarized light and S-polarized light. The flying height of a slider on a glass disk was measured both by an FTIP sensor using this method and by a traditional flying height tester. The results agree with each other with an error of less than 3 nm.