A method of performing a circuit-breaking and closing operation in a three-phase system having a first phase, a second phase lagging the first phase by 120, and a third phase lagging the first phase by 240, includes: a) opening only one of the first phase, the second phase and the third phase before a zero crossing of a current of the corresponding phase, b) opening the remaining phases of the first phase, the second phase and the third phase after step a), and c) closing the first phase, the second phase and the third phase simultaneously or essentially simultaneously at a phase to ground voltage of the phase of the first phase, the second phase and the third phase which lagging the phase that was opened in step a) by 120 in a time range from 60 before a peak of the phase to 90 after the peak.

A method of performing a circuit-breaking and closing operation in a three-phase system having a first phase, a second phase lagging the first phase by 120, and a third phase lagging the first phase by 240, includes: a) opening only one of the first phase, the second phase and the third phase before a zero crossing of a current of the corresponding phase, b) opening the remaining phases of the first phase, the second phase and the third phase after step a), and c) closing the first phase, the second phase and the third phase simultaneously or essentially simultaneously at a phase to ground voltage of the phase of the first phase, the second phase and the third phase which lagging the phase that was opened in step a) by 120 in a time range from 60 before a peak of the phase to 90 after the peak.

A method of performing a circuit-breaking and closing operation in a three-phase system having a first phase, a second phase lagging the first phase by 120, and a third phase lagging the first phase by 240, includes: a) opening only one of the first phase, the second phase and the third phase before a zero crossing of a current of the corresponding phase, b) opening the remaining phases of the first phase, the second phase and the third phase after step a), and c) closing the first phase, the second phase and the third phase simultaneously or essentially simultaneously at a phase to ground voltage of the phase of the first phase, the second phase and the third phase which lagging the phase that was opened in step a) by 120 in a time range from 60 before a peak of the phase to 90 after the peak.

A method of performing a circuit-breaking and closing operation in a three-phase system having a first phase, a second phase lagging the first phase by 120, and a third phase lagging the first phase by 240, includes: a) opening only one of the first phase, the second phase and the third phase before a zero crossing of a current of the corresponding phase, b) opening the remaining phases of the first phase, the second phase and the third phase after step a), and c) closing the first phase, the second phase and the third phase simultaneously or essentially simultaneously at a phase to ground voltage of the phase of the first phase, the second phase and the third phase which lagging the phase that was opened in step a) by 120 in a time range from 60 before a peak of the phase to 90 after the peak.

A localized heating device includes a plasma deforming portion and a heating portion. The plasma deforming portion includes an inlet end having a circular hole, an outlet end having an elongated hole with a first length and a first width, and a channel smoothly connected with the circular hole and the elongated hole. The heating portion, disposed at the outlet end, includes two control covers spaced by a slot. The elongated hole and the slot being oppositely disposed with respect to the plasma deforming portion. A plasma flow provided by a plasma producing source being to enter the channel via the circular hole, then to flow through the elongated hole, and finally to reach the slot.

A localized heating device includes a plasma deforming portion and a heating portion. The plasma deforming portion includes an inlet end having a circular hole, an outlet end having an elongated hole with a first length and a first width, and a channel smoothly connected with the circular hole and the elongated hole. The heating portion, disposed at the outlet end, includes two control covers spaced by a slot. The elongated hole and the slot being oppositely disposed with respect to the plasma deforming portion. A plasma flow provided by a plasma producing source being to enter the channel via the circular hole, then to flow through the elongated hole, and finally to reach the slot.

An independent and multi-unit co-operation stage control system is disclosed herein. The system includes a cloud server, a primary control unit, a secondary control unit and a stage safety monitoring subsystem.

An image processing apparatus includes a sub-image generation unit, a luminance ratio map generation unit, and an electric heating wire pattern estimation unit. The sub-image generation unit generates sub-images by dividing a first image in a lateral direction. The first image is one of a left image and a right image that are captured by a stereo camera through a windshield provided with an electric heating wire. The luminance ratio map generation unit sequentially selects one of the sub-images and generates map data based on the selected sub-image and a second image. The map data indicates a ratio between luminance values. The second image is another of the left image and the right image. The electric heating wire pattern estimation unit performs an estimation of a wiring pattern of the electric heating wire based on the map data regarding each of the sub-images.

An image processing apparatus includes a sub-image generation unit, a luminance ratio map generation unit, and an electric heating wire pattern estimation unit. The sub-image generation unit generates sub-images by dividing a first image in a lateral direction. The first image is one of a left image and a right image that are captured by a stereo camera through a windshield provided with an electric heating wire. The luminance ratio map generation unit sequentially selects one of the sub-images and generates map data based on the selected sub-image and a second image. The map data indicates a ratio between luminance values. The second image is another of the left image and the right image. The electric heating wire pattern estimation unit performs an estimation of a wiring pattern of the electric heating wire based on the map data regarding each of the sub-images.

An electric arc furnace has a safety device (3) connected to an earthed peripheral device. An earth cable (4) is provided to the peripheral device of the arc furnace (2). An ammeter (6) measures the current across the earth cable (4). A circuit breaker (8) in the earth cable (4) has a tripping time of less than 100 ms.