What is a diesel generator? How does it work?

A diesel generator, or "genset" is machinery that converts the chemical energy in diesel to electrical energy. It does this using a diesel engine and an AC alternator, coupled together. They also normally have a fuel tank, control panel and a radiator. You can review the major components of a diesel generator.

You should read how the diesel engine works then how the AC alternator works.

How are diesel generators used?

The diesel engine spins the alternator creating an AC electrical current. This is used to power electrical equipment. They can be used to supply a range of applications such as schools, hospitals, factories and homes. They can be used either as the main source of power or in case of power failure. Generators have different ratings based on the application, there are four main ratings. Emergency Standby (ESP) and Limited Time Power (LTP) for standby applications, Continuous (COP) and Prime Rated power (PRP) when used as a main source of power. Each rating is limited by hours and load factor.

Generators when used as standby, usually have something called a Transfer Switch. This is a mechanical device that stops the generator being connected to the load at the same time as the mains power supply. When the mains power is present, connecting a generator at the same time needs to be done with special controls to run them in parallel. Without this control system, serious damage to the generator can occur, leading to fires. When the mains supply has failed, connecting a generator without isolating it from the mains will lead to back-feeding the grid - potentially killing someone working on restoring the mains supply and probably damaging your generator when the mains returns.

When used as the prime source of power (for example when there is no mains supply, or the mains is too poor to be used) this is referred to as "Island Mode". Where larger requirements for power exist, multiple smaller units can be connected together in parallel, by using a process known as synchronising.

Do they require maintenance?

Diesel generators require careful routine maintenance at regular intervals. This depends on the manufacturer, but the most important item to be serviced typically is the engine. Engines normally require servicing after 250 or 500 hours, but the service interval is defined by the engine manufacturer. If you relate this to a car, driving at 50mph or 80kph, at 500 hours, that would equate to 25,000 miles or 40,000km!

Typically on a routine service you will do a thorough check, change the air filter, oil filter and fuel filter, replace the oil and some of the belts, such as the radiator fan belt and the charging alternator belt.

Maintaining your generator is an important part of ensuring it delivers the electrical power when you need it!