Static Arc Research Articles

Factors affecting the behaviour of an electric arc under transient conditions

The paper describes an investigation into the relationship between voltage and current in an arc under transient conditions. It is shown theoretically that the arc resistance is a function of the energy in the arc column, while the power loss from the arc is a function of arc resistance. The relationship between arc resistance and change of arc energy has been obtained by injecting pulses into a static arc. This relationship is valid for periods from 3 μs up to at least a millisecond. The relationship between power loss and arc resistance has also been derived experimentally. Measurement of the electrode voltage drop under transient conditions has enabled electrode and arc column effects to be separated. It is shown how the relationship between resistance and energy, as well as between power loss and resistance, is affected by a change of arc length, initial arc current and electrode material. Finally, the experimental results are compared with dynamic arc equations published in the literature.

Approximate solution of a non-linear differential equation giving the temperature distribution in the positive column of a static arc

An approximate method is presented for the solution of the differential equation giving the temperature profile of the positive column of a static arc, when heat conduction only is taken into account. The method of Eyres, Hartree and others is first used to change the dependent variable in order to replace the two non-linear functions of temperature present in the differential equation, namely the electrical and thermal conductivities, by a single non-linear function. When this non-linear function is approximated by a piecewise linear function, the basic differential equation can be integrated directly, and the temperature profile obtained. An example shows close agreement with King's results.

Two-Terminal Analysis and Synthesis of Junction Transistor Multivibrators

The basic junction-transistor multivibrator circuit is analyzed from the point of view of a circuit designer who Wishes to know: (a) how to predict the performance of a particular configuration, and (b) how to synthesize a multivibrator circuit, which may be either astable, bistable, or monostable, from a given set of specifications. The analytical method consists of breaking the multivibrator circuit (two basic, well-known configurations are treated) at a suitable point and using, the two terminals thus obtained as a driving-point pair to derive a useful V-I characteristic. In part I of the paper, the static driving-point resistance characteristics arc derived theoretically and compared to experimental measurements. In part II, transient and high-frequency effects are considered and the two-terminal analysis is extended to derive a prediction of the maximum frequency, or pulse repetition rate, at which the regenerative mode of operation can take place. Part III of the paper treats the problem of circuit synthesis. Using the results of parts I and II, straightforward methods are developed which permit the circuit designer to uniquely determine the seven circuit parameters which must be specified in the design of symmetrical multivibrators. Several design examples of astable, monostable, and bistable configurations are given.