Tuesday, December 25, 2007
2-71 Detroit Diesel "Eveready Bunny" generator
I haven't done much to it yet. I added a muffler (still pretty loud), AND I discovered that the voltage was quite high, because it was running at 1800 rpm (90 Hz) instead of 1200! Here it is running at 51 Hz or just over 1000 rpm and 119 volts phase-neutral, into a ~1500 watt load. I probably need to adjust the voltage down to keep it under 130V at 1200 rpm/60 Hz, and let the phase-phase voltage be whatever it is. Anywhere from 208-260 would be fine.
I was happy to find that the overvoltage problem was caused by an overspeed condition; that's easier to fix than a problem in the field control circuit, which is what I initially suspected. 1800 rpm is not enough to hurt the engine; in fact that is a more common running speed for a 2-71 than 1200.
These railroad sets were actually two-speed switchable via a solenoid. They were used on reefer cars; the 1200 rpm position gave rapid cooling and standard 60 cycle electrical power, and they could be switched to 800 rpm for times when demand was lower. This gave 40 cycle power, which simply slowed the 3-phase motors that powered the refrigeration compressors.
I have some ideas for using it in the 40-cycle setting, for reduced noise and fuel consumption.
I plan to run it on waste vegetable oil, at least during the hot summer months.