during the design of power transformer,or any distribution
tfr the load current is taken into account ,and the windings
of the secondary side are accordingly designed that is the
load currents it can sustain ,insulation and cooling system
are taken into consideration...
suppose in your designing u r designed the windings to
sustain a 30 amp load current while reversing the windings
and taking the out put from primary as u stated, the load
current will be decreased at the 415 voltage side and the
current in the 220 voltage ll be increased to a factor of
transformation ratio as it has to work in same power..so the
windings of the 220 side may burnt out..if its not capable
of sustaining the increased current.