Hi,
I don't know the transformer configuration nor the voltage waveform.
I assume you should adjust your winding ratio for the lowest input voltage and the highest output voltage.
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Why 50 Hz switching? Double the frequency and you will need about half the size of the transformer.
( your transformer is about 150kg, isn't it?)
Full wave rectifier with 120A... I expect at least 2V voltage drop, this makes at least 250W of power dissipation. A lot of heat..
Decide synchronous rectifying.
Klaus