Generator units are “work horses” that fulfill the need for
emergency and standby power. They arem available from small 1 kVA units to
those of several thousand kVA. When properly maintained and kept warm, they
dependably come on line within 8–15 s.
In addition to providing emergency power, engine-driven
generators are also used for handling peak loads and are sometimes used as the
preferred source of power.
They fill the need of back-up power for uninterruptible
power systems. Where well-regulated systems, free from voltage, frequency, or
harmonic disturbances, are required, such as for computer operations, a buffer
may be needed between the critical load and the engine-driven generators.
Diesel Engine Generators
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| Diesel Engine Generators |
Individual models by various companies may be different. Lower speed
units are heavier and more costly, but are more suitable for continuous duty.
Diesel engines are somewhat more costly and heavier in
smaller sizes, but are rugged and dependable. The fire and explosion hazard is
considerably lower than for gasoline engines. Sizes vary from about 2.5 kW to
several MW.
Gasoline Engine Generators
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| Gasoline Engine Generators |
Gasoline engines may be furnished for installations up to
about 100 kW output. They start rapidly and are low in initial cost as compared
to diesel engines.
Disadvantages include a higher operating cost, a greater
hazard due to the storing and handling of gasoline, short storage life of the
fuel, and generally a lower mean-time between overhaul. The short fuel storage
life restricts gasoline engines’ use for emergency standby.
Gas Engine Generators
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| Gas Engine Generators |
Natural gas and liquid petroleum (LP) gas engines rank with
gasoline engines in cost and are available up to about 600 kW and higher. They
provide quick starting after long shutdown periods because of the fresh fuel
supply.
Engine life is longer with reduced maintenance because of
the clean burning of natural gas. However, consideration should be given to the
possibility of both the electric utility and the natural gas supply being concurrently
unavailable.
Unless engine compression ratios are increased, engines lose
approximately 15% in power when operated on natural gas, compared to gasoline.
Considerations in selecting natural or LP gas-fueled engines are the
availability and dependability of the fuel supply, especially in an emergency
situation.
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