Magnetic Camera Research Articles

Optical emission from an accelerated compact toroid

This article presents magnetic probe data, interferometry data, and framing camera images of the optical emission from an accelerating compact toroid. The optical emission measured in these experiments includes a bright emission spot near the center of the inner electrode as the compact toroid leaves the accelerator. This bright emission spot is interpreted as a radial compression of plasma trailing behind a compact toroid as the compact toroid leaves its inner electrode.

Study of re-strike phenomena in a low-voltage breaking device by meansof the magnetic camera

To preserve the qualities of the contacts of a circuit breaker, an importantphenomenon to be valued is the arc motion. In this paper, the behaviour of ahigh-current and low-voltage electric break-arc is studied thanks to a meansof diagnostics called `magnetic camera'. One hundred probes measure themagnetic induction outside the breaking device. A processing softwarereconstructs the average line of current representing the arc with a 0.64 µsminimal resolution time, the line being assumed to be composed of segments.The presented study deals with the analysis of a harmful phenomenon for thecircuit breaker: the re-strike during which several arcs exist. Tests havebeen carried out in a quenching chamber composed of a copper or steelsplitting plate with an assumed peak current of 4000 A. One of the maindifficulties of this study taking into consideration the magnetic effects due to steelsplitting plates. Actually, we show that they have a slightinfluence on the location of the line of current.Thanks to the `magnetic camera', the arc positions and their respectiveintensity values are both determined. Besides, differences in behaviour have not beennoticed between the use of a copper and a steel splitting plate.

Development of Magnetic Camera Using 2-D Arrayed Hall Elements(NDE2)

Development of Magnetic Camera Using 2-D Arrayed Hall Elements(NDE2)

A study of the various phases of the break in a low-voltage circuitbreaker thanks to the magnetic camera

By analysing the magnetic induction created by the arc motion from the outside of a breaking system at numerous points, it is possible to determine the position of the average line of current that magnetically represents the arc. This method is called the `magnetic camera' method. It had to be adapted to the circuit breaker studied here. Thanks to the method three phases of the course of the electrical arc are highlighted for a typical experiment: expansion of the arc, commutation from the mobile contact onto the lower rail and displacement through the splitter plates. In order to be more precise about the duration of the commutation phase, during which more than a single line of current must exist, an improved model of the arc motion has been developed.

Evolution of a low-voltage electric arc

The evolution of a low-voltage electric arc is studied with a matrix of microcoils which behaves like a magnetic camera. The arc is assimilated to a series of straight segments. The shape that it assumes in the electrode gap as well as re-striking phenomena are analysed. The influence of insulating and conducting obstacles is stressed.

A magnetic camera for studying the electric breaking-arc

A better knowledge of the electric breaking-arc can be obtained through electrical, optical and magnetic diagnoses. Therefore, a system called 'magnetic camera' has been devised and developed. It consists of a V-shaped matrix, with some 70 probes, each of which gives the shape of magnetic induction versus time in the gap between two electrodes. The various shapes assumed by the arc can be determined by means of data-acquisition and processing software within a few minutes. This type of camera is characterized by a maximum speed of exposure which is five times faster than that of an ultra-high-speed optical camera. Moreover, the diagnosis obtained is closer to the basically electric nature of the arc.