480/240 = 2:1 ratio. So 415 input will give to a 207.5V output. Whether or not the input is Y or Delta is immaterial (but it will be Y by the way). But a standard 480-240V transformer is not going to be Y on the output, it will be Delta only and you need Y on the output, so that isn't going to work. That is likely why waross suggested the other version, it is a way to end up with a Y on the side you need it on. Or like he said, have a custom one made.
If you go custom, then you have another issue. If a transformer is designed for 60Hz, applying 50Hz to it will put it into a low flux situation and the output capacity may be reduced because the magnetizing current will increase. So for the same amount of load on the transformer, it will run hotter at 50Hz and therefore the output capacity at full load will be reduced. So when you have a custom transformer made, make sure they know you are going to be using 50Hz up front, you can get into trouble if they build it for 60Hz.
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