Abstract: A ground fault detection circuit includes an AC power supply and a plurality of resonance circuits. The plurality of resonance circuits are connected between at least one current path formed of a plurality of loads and the AC power supply. Each of the plurality of resonance circuits has the same resonance frequency as the frequency of the AC power supply.

Abstract: A ground fault detection circuit includes an AC power supply and a plurality of resonance circuits. The plurality of resonance circuits are connected between at least one current path formed of a plurality of loads and the AC power supply. Each of the plurality of resonance circuits has the same resonance frequency as the frequency of the AC power supply.

Abstract: A plural number of bridge circuits, each having a rectifier circuit with positive half wave control electrodes and a rectifier circuit with negative half wave control electrodes, and each of the plural number of the bridge circuits is connected to one winding of a power supply transformer; the rectifier circuit with negative half wave control electrodes selected from the plurality of the bridge circuits is electrically conducted when a predetermined the rectifier circuit with positive half wave control electrodes of the plurality of the bridge circuits is electrically conducted; the rectifier circuits with positive half wave control electrodes and the rectifier circuits with negative half wave control electrodes are connected by a plurality of loads.

Abstract: A plural number of bridge circuits, each having a rectifier circuit with positive half wave control electrodes and a rectifier circuit with negative half wave control electrodes, and each of the plural number of the bridge circuits is connected to one winding of a power supply transformer; the rectifier circuit with negative half wave control electrodes selected from the plurality of the bridge circuits is electrically conducted when a predetermined the rectifier circuit with positive half wave control electrodes of the plurality of the bridge circuits is electrically conducted; the rectifier circuits with positive half wave control electrodes and the rectifier circuits with negative half wave control electrodes are connected by a plurality of loads provided therebetween; and electric power of the power supply transformer is fed to the loads selected from the plurality of the loads.

Abstract: An arc control apparatus for a DC arc furnace provides an additional magnetic field which prevents a discharged arc from shifting outward at an arc generating point due to the influences of a magnetic field generated by a feeder circuit, thus directing the arc discharge vertically downward. The arc control apparatus includes an arc furnace in which an object to be melted is disposed. A movable electrode is disposed in the arc furnace for movement relative to the object. A feeder circuit including a power supply and a feeding conductor is connected to the movable electrode and the arc furnace for supplying a voltage therebetween from the power supply through the feeding conductor to generate an arc whereby the object is dissolved. An auxiliary coil is disposed outside and in the vicinity of the arc furnace and connected to the feeder circuit for generating a counter magnetic field in a direction to cancel a magnetic field which is generated at a point of generation of the arc by means of the feeder circuit.

Abstract: An alignment of a light guide (10) and a photosensitive portion (1a) of an element (1) in a light-triggered thyristor is adapted such that, in order to eliminate a deviation or offset between the light guide and the photosensitive portion, an inner peripheral surface of a positioning ring (11) attached to an inner wall surface of an insulating cylinder (5) is machined, with respect to an axial center line which is a line extending to a tip portion of the light guide (10) on the element side, attached to the insulating cylinder (5), so that an inner diameter of a ring is made slightly larger than an outer peripheral surface of a reinforcing metal disc (2) to which the element (1) is fixed coaxially and the reinforcing metal disc (2) is inserted into the positioning ring (11).

Abstract: A light triggered thyristor device is improved by providing a light guide having a taper portion and acting to condense incident light while being constructed so as to achieve total internal reflection of the light passing therethrough. With this construction, the exit end of the light guide, as well as the light receiving portion of the thyristor, can be reduced in size.