375 rpm is rather slow, its going to be hard to meet 30 watts at that speed.
keep in mind at a more reasonable 3600 rpm, you would get 300 watts with the same torque. if you figure 50% efficiency at 30 watts and 370 rpm, you would have a 1 hp generator at 3600 rpm and 90% efficiency and that's just copper loss, ignoring windage and iron losses which escalate real quick.
A 1/4th hp 1800rpm 90v dc motor would be more suitable for what you need. at 375 rpm you'd get about 18-22 volts.