how to calculate the secondary current of the transformer for example 1200 amps in primary ,primary voltage is 220kv and the secondary voltage is 34.5 kv of the transformer .
That is a good answer 7652 amps. 7300 amps is more realistic, considering transformer losses, but I don't think any one has built that large a transformer, so surprises are likely. Even at 1% that many amps, 3 phase is likely. Neil
For an ideal transformer, the voltage ratio is set by the turns ratio, so the transformer is a stepdown with the ratio of 220/34.5. The current ratio is also set by the turns ratio, but current goes up as voltage goes down, so the secondary voltage is 1200 x (220/34.5). Again, for an ideal transformer only.
