Why Use Diesel Generators
Diesel Generators are most preferred way to Generate Power for emergency, stand
by power generation and to increase the capacity of existing Generating Stations.
Diesel combustion does not produce carbon mono-oxide a worst pollution so it is
much safer than Nuclear, Hydro Power or Petrol Generators.
Diesel powered generators, or electrical generator sets, are used in countless industrial
and commercial establishments. The generators can be used for small loads, such
as in homes, as well as for larger loads like industrial plants, hospitals, and
commercial buildings. They can either be prime power sources or standby/back-up
power sources. They are available in various specifications and sizes. Diesel generator
sets rating 5-30KW are typically used in simple home and personal applications like
recreational vehicles. Industrial applications cover a wider spectrum of power ratings
(from 30 kW to 6 Megawatts) and are used in numerous industries throughout the globe.
For home use, single-phase power generators are sufficient. Three-phase power generators
are primarily used for industrial purposes.
Diesels sound scary to some people who are unfamiliar with them, but they are actually
simpler in design and construction than gas engines. It requires less service. The
only maintenance generally required is changing the oil, and changing the fuel,
air, and oil filters. This much is the same as on a gas engine. What you won’t have
to deal with is tune-ups. No carburetor adjustments, no distributor or magneto to
burn out, and no spark plugs to need periodic cleaning and replacement.
 Diesel
generators can be operated together (in parallel). The use of parallel running generators
provides the advantages of more capacity, efficiency and redundancy. A power plant
driven by diesel generators will typically include between three and six machines.
Generators can be connected together through the process of synchronization. Synchronization
involves matching voltage, frequency and phase before connecting the generator to
a live busbar. Failure to synchronize before connection could cause a high current
short-circuit or wear and tear on the generator and/or its switch gear. The synchronization
process can be done automatically by an auto-synchronizer module. The auto-synchronizer
will read the voltage, frequency and phase parameters from the generator and busbar
voltages, while regulating the speed through the engine governor or ECU (Engine
Control Module). Load can be shared among parallel running generators through load
sharing. Like auto-synchronization, load sharing can be automated by using a load
sharing module. The load sharing module will measure the load and frequency at the
generator, while it constantly adjusts the engine speed to shift load to and from
the remaining power sources. As the prime mover of a diesel generator runs at constant
speed, it will take more active load when the fuel supply to its combustion system
is increased, while load is released if fuel supply is decreased.
AMF Panel can automatically start and stop diesel generators in case of mains failure
and restoration.
Diesel engines can suffer damage under certain conditions that are sometimes encountered
when used in a generating set- namely internal glazing and carbon buildup due to
prolonged periods of running at low speeds and/or low loads. Such conditions may
occur when an engine is left idling as a 'standby' generating unit, ready to run
up when needed, if the engine powering the set is over-powered for the load applied
to it by the alternator, or if the generator set's maximum output is far in excess
of the normal loads placed on it, causing the diesel unit to be under-loaded. This
is a common problem in generator sets. For example, a diesel generator set powering
the lighting circuit of a building would be designed to be able to cope with the
load of every light in the building being on. However, this situation rarely occurs,
so for the vast majority of its operating life the diesel engine in the set will
not be heavily loaded (maybe as little as 10% of the maximum load). Ideally diesel
engines should run at least around 60-75% of their maximum rated load, and at around
75% of their maximum speed (although the phasing requirements of engines in generator
sets can make these speeds hard to achieve). Glazing occurs due to low combustion
temperatures and pressures in the engine cylinder. When an engine is loaded correctly,
the load resists the movements of the crankshaft and piston during combustion. This
causes the combustion pressure to rise as the volume of the cylinder cannot increase
directly in line with the increase in pressure during combustion. Running an engine
under low loads low cylinder pressures and consequent poor piston ring sealing –
these rely on the gas pressure to force them against the oil film on the bores to
form the seal. Low initial pressure causes poor combustion and resultant low combustion
pressures and temperatures. This poor combustion leads to soot formation and unburnt
fuel residues which clogs and gums piston rings. This causes a further drop in sealing
efficiency and exacerbates the initial low pressure. Glazing occurs when hot combustion
gases blow past the poorly-sealing piston rings, causing the lubricating oil on
the cylinder walls to 'flash burn', creating an enamel-like glaze which smooths
the bore and removes the effect of the intricate pattern of honing marks machined
into the bore surface. Hard carbon also forms from poor combustion and this is highly
abrasive and scrapes the honing marks on the bores leading to bore polishing, which
then leads to increased oil consumption (blue smoking) and yet further loss of pressure,
since the oil film trapped in the honing marks maintains the piston seal and pressures.
Un-burnt fuel leaks past the piston rings and contaminates the lubricating oil.
At the same time the injectors are being clogged with soot, causing further deterioration
in combustion and black smoking.
The most important class of three-phase load is the electric motor. A three phase
induction motor has a simple design, inherently high starting torque, and high efficiency.
Such motors are applied in industry for pumps, fans, blowers, compressors, conveyor
drives, and many other kinds of motor-driven equipment. A three-phase motor will
be more compact and less costly than a single-phase motor of the same voltage class
and rating; and single-phase AC motors above 10 HP (7.5 kW) are uncommon. Three
phase motors will also vibrate less and hence last longer than single phase motor
of the same power used under the same conditions. Large air conditioning, etc. equipment
use three-phase motors for reasons of efficiency, economy and longevity. Resistance
heating loads such as electric boilers or space heating may be connected to three-phase
systems. Electric lighting may also be similarly connected. These types of loads
do not require the revolving magnetic field characteristic of three-phase motors
but take advantage of the higher voltage and power level usually associated with
three-phase distribution. Fluorescent lighting systems also benefit from reduced
flicker if adjacent fixtures are powered from different phases.
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