A Dynamic Electroheat Model for an AC Plasma Torch

A lumped-parameter dynamic model of the thermal characteristics of an ac plasma torch is developed. Particular emphasis is placed upon developing a model directly suited to the requirements of automatic control analysis. It is shown that the magnetic flux density and supply voltage are desireable control inputs since they lead to the least complex dynamic representation. A state-variable approach is adopted, and the system matrix coefficients are evaluated for a typical plasma torch configuration. The variations of these coefficients with gas flow and magnetic flux density are determined. The model will be of use to engineers concerned with the application and control of plasma torches in electroheat processes.