I have a 7.5 hp motor that was wired 480 volts 3 phase rated at 14 amps and I need to change from 480 volts down to 208 volts. What would the breaker size need to be rated for at that voltage.

It should be sized according to Table 430.150 of the NEC, and a 7.5 HP motor is rated at 24.2 amps, and the breaker can be no larger than 250%, or 60 amps.

Don't forget to change the overload heaters that should be in the mag starter controlling the motor. These need to be 125% of the actual running load amps.

I have a travel trailer that is only 30 volts. This limits what can be running at the same time. I would like to change the trailer to 50 volts. Can that be done?