Converting 120-volt AC (alternating current) to 240 volt AC will allow you to use higher-voltage appliances without a proper 240-volt supply. Thanks to Ohm's law, we know that current (A) multiplies with voltage (V) equals power in watts. Therefore, increasing the voltage will result in a lower amount of current, but the same power output. Be sure to check the wattage requirements of your load before connecting it to the transformer to be sure that there will be enough power to operate it.
Things You'll Need
120V to 240V step-up transformer
Extension cords (optional)
Select an appropriate transformer. To increase voltage from 120 to 240 volts, you will need a step up transformer with a turn ratio of 1:2. This will double the voltage output and halve the current, but the power output in watts will remain the same, less any losses due to inefficiencies. For example, a standard 120-volt, 15-amp household power outlet will be transformed into 240 volts at 7.5 amps, both outputting a maximum of 1,800 watts.
Connect the output power terminal from the 120V generator to the primary coil side of the transformer. Use either an extension cord, or the cable from the primary side of the transformer (if equipped).
Connect the load to the labeled secondary side of the transformer. This should be the load that requires 240 volts but draws no more than 7.5 amps. The power rating of the load appliance should be no more than 1,800 watts.
Turn on the 120-volt generator. Once running, the generator will begin outputting 120 volts and the transformer will convert it to 240 volts through the transfer of the electromagnetic fields between the transformer's two coils.