High Current Arc Discharge Phenomena with Particular Reference to the Plasma Torch

  • J.E. Harry

    Student thesis: Doctoral ThesisDoctor of Philosophy


    The purpose of this investigation was to study high current
    arc discharge phenomena with particular reference to the plasma
    torch, The principle object was to provide basic information where
    required to enable the factors affecting the operation of a plasma
    torch used for industrial process heating to be evaluated. This has
    been achieved.

    An extensive literature survey of
    ( i) Arc discharge processes relevant to the operation of a plasma torch, -
    (ii) Existing arc devices used for heating gases
    has been made. A plasma torch operated from both direct current and
    alternating current has been used to establish the areas where further
    research was required.

    The preliminary investigations indicated that further fundamental
    information on the behaviour of arcs rotated at high velocities
    between co-axial electrodes in an axial magnetic field was necessary.
    In particular the conditions required for the apparently diffuse nature
    of the arc that had been observed at high rotational velocities and the
    variation of the erosion rate of the arc electrodes with arc velocity
    were required, These were investigated experimentally and the results
    employed in an a.c. plasma torch operating at 410V 50 Hz at power
    inputs up to 60 kW and with conversion efficiencies greater than 60%,
    measured in terms of electrical power input to the arc and the useful
    heat output.

    The results from the literature survey, basic investigations
    and the final version of the plasma torch have been used to establish
    the design criteria for a d.c,. or a.c, plasma torch suitable for
    industrial process heating.

    In addition results of a wider application have been obtairad
    including the development of a synchronous switch suitable for supplying
    accurately controlled high current pulses, improved methods of
    arc ignition and a new definition of arc stability that enables quantitative
    measurements of arc stability to be made.
    Date of Award1968
    Original languageEnglish


    • high current arc discharge
    • plasma torch

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