I need a 10-15 : 1 step-down transformer for an electrolysis project. It needs to be capable of about 150A. I have an old ex-military transformer/rectifier, but it outputs 200A at upto 230V DC. It has a humungous transformer in it , and some banks of BIG diodes, so if I get a variac from ebay that will handle 0-240V ac at about 15-20A, and feed the output of that into the transformer, I'm thinking I should get 0-24V at 150A no prob. Obviously, the diodes and rest of it provide the most awesome DIY rectifier kit in the world. The one problem is that the transformer is 3 phase. It has inputs of 440,415 and 380 V, and outputs of 220,210 &200 V. There is also a 0 and 30V connection. There is a second 0 which has tabs for + & - 2% on either side. I guess this is for the neutral input. Questions: 1) The transformer is in the form of 3 coils, all on the same laminated frame but with about 50mm air gap between them. The frame runs the full width top and bottom, but not down between the individual coils. What will happen if I connect one of the 3 coils to 240V supply. Will the others, which are on the same laminated core frame, be energised and cause problems? I only need to use one of the coils. 2) I fear that the inrush current might suck the whole of the national grid into my workshop and turn the universe into a huge black hole! Could I feed the input through a 30A triac, and start with it turned off, to build it up slowly, or would the triac stand no chance? 3) If it won't work well in its 3 phase form, would it be ok to cut the frame between the coils with a Stihl saw, and use the coils separately?