You're right about the MOVs, I can't find one rated for more than 10k-100K transient cycles at 150 amps, more of a sacrificial part than I want. TVS diodes may be the way to go as a shunt to soak up reactor spikes when breaking the arc, will investigate, thanks for the tip! Still wondering about a heavy cap in parallel with the output to help with arc stabilization, maybe not needed after all and just another source of oscillation in the loop between reactor, arc, and cap plates? I'm not sure if the Wye system with all the little peaks at the same frequency is going to set up oscillations within the three phase generator circuits or not, am thinking most of the oscillations will be on the DC-output side (welding lead circuit) because that's where the regulator is connected. The alternator's original self-exciting internal circuit had two sets of diodes: a bridge rectifier and another diode which may act as a snubber to prevent loops between the field circuit and the rectified field supply circuit, plus there are diodes in the voltage regulator according to schematics. I bypassed all that because it isn't rated for more than automotive voltage anyway, may have to look at the alternator schematic again and see if I can't duplicate some of the circuitry with higher-voltage components. The auto system also has the advantage of a huge honking battery to soak up a lot of current fluctuations, which the whole reason I feel I will need a reactor in series with the welding lead.