Standby or Prime Power, Single Phase or Three Phase Power and Operating Speed?
The first determination you will need to make is whether you will require standby or prime power. Simply stated, prime power is required when you have no other source of power. A standby set is a backup to normal utility power.
Generator sets produce either single or three-phase power. Choose a single phase set if you do not have any motors above five horsepower. Most homeowners will require single phase whereas industrial or commercial applications usually require three-phase power. Three-phase generators are set up to produce 120/208V, 277/480 or 347/600 volts output. Single-phase sets are 120V or 120/240V. Use the low voltage to run domestic appliances and the high voltage for your motors, heaters, stoves and dryers.
Electric equipment is designed to use power with a fixed frequency: 60 Hertz (Hz) in the United States and Canada, 50 Hertz in Europe and Australia. The frequency output of a generator depends on a fixed engine speed. To produce 60 Hz electricity, most engines operate at 1800 or 3600 RPM. Each has its advantages and drawbacks. 1800 RPM, four pole sets are the most common and least expensive. They offer the best balance of noise, efficiency, cost and engine life. 3600 RPM, two pole sets are smaller and lightweight, best suited for portable, light-duty applications.
In simple terms it’s like operating your car at 90 mph, versus 45mph – at 45mph your car will last longer, is quieter, less maintenance and longer life. Most 3600 rpm units are twin cylinder air cooled lawn mower engines, while the water cooled 1800 rpm units are comparable to those found in forklift and tractor engines…the 1800 rpm water cooled units will last longer, offer less maintenance problems and be more fuel efficient.