Abstract: A control system of pumping operation comprises a cycloconverter for converting AC power from a AC power system into AC power having a given frequency, anAC exciting generator-motor, having a stator side electrically connected to the AC power system, having a rotor side electrically connected to the cycloconverter, and having a rotor shaft mechanically coupled to a pump-turbine by which the pumping operation is carried out, a circuit breaker inserted between the AC power system and the AC exciting generator-motor, a rotation speed controller for controlling a rotation speed of the AC exciting generator-motor such that the rotation speed becomes slow when the pumping operation is to be stopped, an AC excitation controller for decreasing a degree of excitation effected by the cycloconverter, wherein decreasing of the excitation degree starts when the rotation speed of the AC exciting generator-motor reaches a given minimum value, and a circuit breaker controller for turning off the circuit breaker when input po

Abstract: A method of igniting arcs wherein an electric field is formed in the vicinity of an electrode and ignition-plasma is projected against a cathode in the electric field, to thereby ignite an arc.

Abstract: In an optical measuring device which comprises a polygonal rotary mirror for reflecting an incident light beam into a rotary scanning light beam, a collimator lens for converting the rotary scanning light beam into a parallel scanning light beam and a light receiving element for detecting bright and dark portions of the parallel scanning light beam, which has scanned a work to be measured, and a time duration of the dark portion or the bright portion is detected, which has been generated by the obstruction of a part of the parallel scanning light beam by the work, to thereby determine a dimension of the work, the collimator lens is made to be an f.theta. lens having such a spherical aberration that a light beam incident from the outlet side of the collimator lens toward the polygonal rotary mirror in parallel to the optical axis of the lens intersects the optical axis of the lens at a position shifted from a focal point on the inlet side to the outlet side by .DELTA.

Abstract: A microscope wherein a plurality of objective lens barrels (25) are mounted to a disk (23) in such a manner that the axial lines thereof are in parallel with the center axis of the disk (23), the disk (23) is rotatably provided on the undersurface of an upper frame (12A) of the main body (12) in such a manner that the axial line thereof is in parallel with the optical axis (18) of the main body, a large diameter screw (50) having a recess (50B) is affixed to the top surface of the upper frame (12A) a three lens barrel (13) is rested on this large diameter screw (50) and fixed to the large diameter screw (50) through a clamp member (14), and further, rectangular prisms (60) and a roof prism (74) for making it possible to visually observe a non-inverted image are provided in the three lens barrel (13).

Abstract: A method for stopping a multi-stage hydraulic machine with an inlet valve, guide vanes including highest and lowest stage guide vanes, and a return passage connected between flow passages of respective stages, wherein the machine is in turbine operation, including the steps of initiating the closing of the highest stage movable guide vanes firstly and the lowest stage movable guide vanes secondly and judging whether a closing relation between the highest and lowest stage vanes is normal or not in accordance with predetermined criteria after initiation of closing the lowest stage movable guide vanes. The method includes the steps of controlling the closing of the lowest stage movable guide vanes based on the judgement result, and the step of closing the inlet valve.

Abstract: A method for TIG welding by using a plurality of nonconsumable electrodes extending frm the tip of a TIG welding torch and one filler wire fed through a space between the electrodes, each electrode being independently supplied with power. A molten pool is formed by melting both the base metal to be welded and the filler wire by means of arcs generated between respective electrodes and the base metal. Melting of the base metal is mainly controlled by the arc produced by one of the plurality of electrodes while melting of the filler wire is mainly controlled by the arc generated by the other electrode.