I have one auto transformer that we used to convert 3-phase 380V to 3-phase 220V. Now I need to convert 3-phase 220V to 380V. How to use the same transformer for 3-phase 380V output? Please explain the procedure.
If this is a fixed multi taped transformer reversing the input and output will change it from a step up to step down (I an used to auto transformers as variable not multi tapped) if variable Google variacs the connections will Need to be changed stepping down is simple the entire coil is normally used and a wiper provides voltage at the position, stepping up is a little diferent. Taps at approx 10 or 20% in are connected to the line voltage providing a higher output voltage . added: after doing a quick look at 3 different variacs all 3 were only able to tap up 10% of the line voltage so you probably would only be able to reach approx 250 v in a step up mode.