adjacent half cycles always equaling 360 u00b0 the welding current is forced to reverse rapidly by a substantial voltage to insure conduction when the welding load is an arc to an aluminum work piece and the aluminum tends to rectify the heights of the positive and negative half cycles are simultaneously adjustable in response to manual control and feedback signals in addition the ratio of the heights of the positive and negative half cycles can be other than 1 1 by selectively enabling a conduction path through a different number of turns on the inductor during the negative and positive half cycles such enabling being either continuous or on an adaptive feedback basis as a function of arc length as determined by arc voltage the height difference is effective in a step fashion since the total ampere turns must remain constant the thyristor network may also be re connected for full wave rectification for d c welding application_number US 57568575 A description fig1 is a schematic circuit diagram of a prior art a c welder supply of the type shown in the aforementioned u s pat no 3 364 334 in this prior art circuit a variable a c source is connected across the input terminals 10 and 12 of a welding transformer across whose secondary output terminals 14 and 16 appears the single phase a c voltage e 2 a diode bridge 18 is connected in series between the terminal 14 and the welding electrode terminal 20 the terminal 22 is connected to the work to be welded and during welding an arc is struck between the electrode and the work the external bridge terminals 24 and 26 are termed the.