Operating Characteristics of a kW Class Cascade Plasma Torch with External Magnetic Field

Abstract

The voltage measurements were conducted for a kW class cascade plasma torch with an external magnetic field. Pure argon was used as working gas at atmospheric pressure. To study the voltage-current characteristics of the plasma torch, the operating current and the anode-cathode distance were changed from 40 A to 100 A and 0 mm to 10 mm, respectively. The external magnetic field was applied by a permanent magnet with the maximum strength of about 0.39 T, generating about 0.27 T on the center axis of the plasma torch. The results show that applying the external magnetic field and separating the anode-cathode distance tend to increase the time-averaged voltage for each operating condition. With the external magnetic field, the amplitude of the voltage fluctuation is reduced under certain conditions where the power spectra of the arc voltage show a peak around 2 kHz. This peak is attributed to the arc rotational movement.