The suitability for welding of manual metal arc welding transformers depends on the no-load voltage and on the electro-magnetic behaviour of the reactor. The latter is related to the curvature of the actual magnetization characteristic. The analysis aims at the quantitative establishment of that dependency. The fulfilling of the imposed task is performed through the approximate evaluation of the current waveforms in the two simplified welding circuits that have been designed with equal parameters except the data of the reactors. The reactors have diverse magnetic circuits and when altering the two extreme working duties of the transformers, a distinctive difference arises between both the changes (for both reactors) of the magnetization characteristic curvature. The evaluation is done with a specially elaborated numerical method. When considering the results the two transformers with nearly the same proportions of the current shape at one working duty, appear to have entirely different proportions at the other working duty.