"...the risk of a fire from overloading the outlet?"
Assuming that the receptacle is wired according to the NEC, there will be no fire.
Why would you expect it to catch fire? Do your other household receptacles burst into flame occasionally? Probably not, I would guess. That's because they are protected with circuit breakers of the correct rating, are fed by the correct gauge of copper wire, and are wired correctly.
For comparison, a typical microwave oven draws 1200 Watts. A typical large transformer, such as a Lionel ZW, draws 275 Watts. That's the equivalent of about 3, 100-Watt light bulbs, or one-third of the microwave.
