Electric Characteristics of Plasma Arc Produced by Bi-Anode Torch

In order to improve the voltage of the plasma arc used for thermal spray, a new plasma torch was designed and constructed. The torch, called bi-anode torch, has two anodes that were inter-insulated and have different distances from the cathode tip. The position of the arc root can be controlled to attach to either anode surfaces during operation. When the anode arc root attached to the first anode, which is near to the cathode, the arc behaves just like a normal one and the arc root position can be determined by Steenbeck’s minimum principle. When it is attached to the second anode, the arc voltage is remarkably enhanced because the arc length is increased. Experimental work has been carried out to compare the electric characteristics of the arcs whose anode roots were attached to different anode surfaces. The results show that the arc has different electric characteristics when changing the anode arc root from first anode to second one. Their mechanisms were discussed in this investigation.