1 Answer

Portable generators are used to provide limited amounts of electric power for a home or building during power outages. In isolated areas not reached by power lines, the generators serve another useful function by making electricity temporarily available. While the majority of generators sold for home use run on gasoline, some models use diesel fuel, natural gas or propane. The cost, size and weight of a generator depend on the wattage of its output as well as the capacity of its fuel tank. Many portable generators that put out over 5,000 watts are too heavy to be lifted and come with wheels and handles for moving. A generator typically has one or more 120-volt AC sockets for extension cords, to carry power to where it is needed. High-wattage generators may also include a 220-volt option. In most situations, users connect individual appliances such as space heaters, refrigerators or televisions to the generator. Others connect the generator directly into the home circuit breaker box or fuse box to supply power to the entire household system, but this can be dangerous.

Conversion from Internal Combustion to AC Electric Power
Once it has fuel in its tank, a generator is started either with a lawnmower-style pull cord or (in some models) a battery-powered electric starter. In a gasoline-powered generator, the starting procedure requires opening the fuel line, priming the engine with a choke switch, and backing off the choke once the engine is running properly. An alternator (or generator head) takes the energy generated by the internal-combustion engine and converts it to electricity. A speed governor ensures that the engine runs at 3,600 rpm, and the 120-volt output is locked in by a voltage regulator. While home-use generators are capable of running for many hours with pauses only for refueling, most (in particular the smaller models) are not designed to operate for days on end. It is also important to keep up with regular oil changes, as specified in the owner's manual.

Limitations and Hazards
Every generator has a wattage rating that cannot be exceeded. If too many appliances are connected and turned on while the generator is running, the unit's circuit breaker will cut off the power to all outlets and will need to be reset with a button on the generator. To stay within the wattage limit, the user must know the total wattage the appliances require. The owner's manuals for many generator models contain a chart of the average wattages required by many household appliances. The wattages of the appliances, added up, must be less than the rated output of the generator. If the wattages exceed the output, some appliances must be turned off. To prevent the risk of fire or melting of cords, heavy-gauge extension cords must be used to connect appliances (especially high-wattage heaters) to the generator. The generator must be properly grounded with a ground wire before being turned on. Since generators produce carbon monoxide and generate considerable heat while operating, ample ventilation (in other words, outdoor operation only) is essential. Generators require shelter from rain or snow and must rest on dry ground, necessitating operation in an open garage doorway or under a special shelter. Finally, electric utility crews typically advise against wiring a generator into the home electrical system, which can cause not only a fire in the home but also a dangerous external power surge when power is restored to the grid. The directions and cautions in the owner's manual must be closely followed.

Read more: How Do Portable Generators Work? | eHow.com http://www.ehow.com/how-does_4914640_portable-generators-work.html#ixzz25oV2WAOp