i don't know why you would ever need such a transformer in real life.
there are weird cases where something needs 30 amps at 120vac, but that's about it.
you can wire it as a 120-240v auto transformer and get a 3:1 ratio which would be useful for generating the actual neutral point from a rotary phase converter if its run from the american 120/240v service, but again, why would you need that, i don't know. (without an isolation transformer the generated neutral is still floating and can't be grounded)