Without an isolation (or step down) transformer. Your 20 ampere circuit breaker can happily trip when oven hot wires touches ground by using proper hot, neutral and grounding wire sizes. No problem about it.
But when you add an isolation (or 220/110v step down) transformer. There is now the core size that can limit the current. So when you use small size transformer, and the wire touches ground in the oven (given proper wire sizes for all), the 20 ampere circuit breaker can no longer trip because the core limits the current, right?
What must then be the proper transformer size given 20 ampere circuit breaker. Does it mean I need to buy a 20 ampere 220v-110v transformer even if the oven is only 1 ampere just to make it trip?
Note I live in a country with only 220v output and let's say I need to use an important equipment that is rated only at 110v. I don't know the answer above so even if the answer is obvious. Please confirm it.