A study on medium voltage power conversion system for plasma torch

This paper investigates the medium voltage power conversion system for plasma torch application. The plasma torch rated for 3MW, 2kA and having the physical size of 1 m long is selected. The dynamic characteristics of the DC arc in plasma torch are investigated using advanced 3D magneto-hydrodynamics simulation. The parameters of Cassie-Mayr arc model are calculated based on 3D simulation. Two-phase staggered series connected 3-level dc/dc converters is proposed to be a suitable power converter topology. Simulation shows that the ripple of arc current can be maintained within plusmn11.5% of its rated value, 460A under the existence of load disturbance of plusmn10% in arc voltage. This power converter topology provides high ignition voltage around 5kV during ignition phase and high arc stability under the existence of intrinsic arc disturbance noise.