Saturday, January 24, 2009

Diesel generator

A diesel generator is the combination of a diesel engine with an electrical generator (often called an alternator) to generate electric energy. Diesel generating sets are used in places without connection to the power grid or as emergency power-supply if the grid fails. Small portable diesel generators range from about 1kVA to 10kVA may be used as power supplies on construction sites, or as auxiliary power for vehicles such as mobile homes.

The packaged combination of a diesel engine, a generator and various ancillary devices such as base, canopy, sound attenuation, control systems, circuit breakers, jacket water heaters, starting systems etc, is referred to as a generating set or a gen set for short.
While the larger industrial generators can range from 8kVA - 30kVA for homes, small shops & offices up to 2000kVA used for large office complexes, factories. A 2000 kVA set can be housed in a 40ft ISO container and be fully packaged and portable. Sizes up to about 5 MW are used for small power stations and these may use from one to 20 units. In these larger sizes the engine and generator are brought to site separately and assembled along with ancillary equipment
Diesel generators, sometimes as small as 250 kVa are widely used not only for emergency power, but also many have a secondary function of feeding power to utility grids either during peak periods, or periods when there is a shortage of large power generators.

Diesel generator on an oil tanker
Ships often also employ diesel generators, sometimes not only to provide auxiliary power for lights, fans, and winches, etc. but also for main propulsion. With electric propulsion the generators can be placed in a convenient position, to allow more cargo to be carried. Electric drives for ships were developed prior to WW I. Electric drives were specified in many warships built during WW II because manufacturing capacity for large reduction gears was in short supply, compared to capacity for manufacture of electrical equipment. Such a diesel-electric arrangement is also used in some very large land vehicles.
Generating sets are selected based on the load they are intended to supply power for, taking into account the type of load, ie emergency or for continuous power, and the size of the load, and size of any motors to be started which is normally the critical parameter.

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