A generator set typically consists of an engine and a generator that are mounted together as a single unit. In certain applications, a generator set may include other components, such as a fuel container, voltage regulator, or an inverter. The primary function of the set is for the electrical generator to convert mechanical energy from the engine into electrical energy. Generator sets can run on a variety of fuel sources, and are often used in locations where electrical power isn't available or has been interrupted. They can range in size from small, hand-operated units to larger sets that are installed in vehicles, on trailers, or even in buildings.
Many generator sets include components other than the necessary engine and electrical generator. Portable generator sets typically include a fuel tank. This can allow these compact, hand-operated units to be moved around as necessary without concern for an additional fuel source. Many other generator sets include things like speed governors to control the rotational speed of the engine; voltage regulators to tightly control the voltage output; and inverters to help make the electrical output better-suited to running delicate electronics.
A generator set can technically run on any fuel source that can power the engine component. Some of the most common fuel sources are often things like gasoline, diesel, propane, and natural gas. The smaller, hand-operated units most often run on gas, while larger, building-mounted units generally be connected to natural gas, if it is available, or operate on tanks of diesel in other applications. Vehicle-mounted generator sets, such as those found in recreational vehicles, often use the same fuel source as the main engine of the vehicle itself. Such units may also have their own fuel tanks if the generator engine and vehicle engine run on different kinds of fuel. If the unit runs on liquefied petroleum gas (LPG), it may simply be connected to the propane tank.
One potentially useful application for a generator set is as a back-up power supply in critical installations. Buildings such as hospitals — where an interruption in power could lead to a loss of life or other undesirable, costly damages — often make use of integrated generator sets. In these cases, a large generator set will often be installed on-site and wired into the building via a tie-in panel. The specifics of the installation will vary, though systems exist that automatically start the generator set after a power failure, switch the building from the failed grid power to the generator, and then shut the generator off again once power has been restored.