Abstract: A commutation type DC breaker comprising a main switch inserted in series into a main circuit for connecting a DC source and a load, a commutation capacitor, a reactor, and a commutation switch for supplying charges stored in the commutation capacitor to the main switch in an opposite direction to a main circuit current, producing a current zero point, thereby breaking the main switch, characterized in that the commutation capacitor, the reactor, and the commutation switch which are composed a commutation circuit and a control circuit for controlling the turning on or off of the main switch and the commutation switch are loaded on a frame with the main switch loaded.

Abstract: A commutation type DC breaker comprising a main switch inserted in series into a main circuit for connecting a DC source and a load, a commutation capacitor, a reactor, and a commutation switch for supplying charges stored in the commutation capacitor to the main switch in an opposite direction to a main circuit current, producing a current zero point, thereby breaking the main switch, characterized in that the commutation capacitor, the reactor, and the commutation switch which are composed a commutation circuit and a control circuit for controlling the turning on or off of the main switch and the commutation switch are loaded on a frame with the main switch loaded.

Abstract: A power use circuit breaker includes an arc generating switching unit which adds an electrical resistance in a circuit during current interruption to attenuate a current to be interrupted, a vacuum bulb which is electrically connected in series with the arc generating switching unit and interrupts the attenuated current and a current conducting switching unit connected in parallel with the series circuit of the vacuum bulb and the arc generating switching unit. For current conduction the current conducting switching unit is closed after the vacuum bulb and the arc generating switching unit are closed, and for current interruption after opening the current conducting switching unit, the vacuum bulb and the arc generating switching unit are opened.

Abstract: A power use circuit breaker includes an arc generating switching unit which adds an electrical resistance in a circuit during current interruption to attenuate a current to be interrupted, a vacuum bulb which is electrically connected in series with the arc generating switching unit and interrupts the attenuated current and a current conducting switching unit connected in parallel with the series circuit of the vacuum bulb and the arc generating switching unit. For current conduction the current conducting switching unit is closed after the vacuum bulb and the arc generating switching unit are closed, and for current interruption after opening the current conducting switching unit, the vacuum bulb and the arc generating switching unit are opened.

Abstract: An arc generating switching unit 2 which adds an electrical resistance in a circuit during current interruption to attenuate a current to be interrupted, a vacuum bulb 1 which is electrically connected in series with the arc generating switching unit 2 and interrupts the attenuated current and a current conducting switching unit 3 connected in parallel with the series circuit of the vacuum bulb 1 and the arc generating switching unit 2 are provided, and for current conduction the current conducting switching unit 3 is closed after the vacuum bulb 1 and the arc generating switching unit 2 are closed, and for current interruption after opening the current conducting switching unit 3, the vacuum bulb 1 and the arc generating switching unit 2 are opened. Thereby, a small sized power use circuit breaker which performs current conduction and interruption of a large current containing a DC component is obtained.

Abstract: A gas insulated circuit breaker includes a closed tank filled with an insulation gas, one pair of separable contacts disposed in the closed tank, a supporting frame supporting the closed tank, an opening spring for performing an opening operation of the pair of contacts, a closing spring for performing a closing operation of the pair of contacts, and an actuating mechanism box accommodating an opening coil which is adapted to receive a circuit opening command for the contacts, a closing coil which is adapted to receive a circuit closing command for the contacts and an actuating mechanism for rendering the opening spring and the closing spring operative in response to an activation of the opening coil and the closing coil. A first spring casing accommodates the opening spring and is secured on the closed tank, and a second spring casing accommodates the closing spring and is secured on the supporting frame.