In order to improve the efficiency of high power plasma torches, we have studied the cold crucible with TRIFOU, the 3D electromagnetic field computation software developed by EDF. The computation gives information that can not be obtained experimentally, (e.g.: current distribution) but that is necessary for efficiency improvement. We also give
the influence of parameters such as the number and the thickness of the cold crucible sectors. It is then possible to define the characteristics of the best torch, depending on the fact we want a good efficiency, a high power
in the plasma or a low power loss.