system.
In
areas
with
several
periods each day.
Extreme caution
generator
locations,
a
standby
must be used if the 60 percent and 40
generator is provided for each three
percent generators are used at the
or four generator locations.
This
same time to meet a maximum (100
generator is moved to the proper
percent) demand.
It requires highly
location when one generator is taken
skilled
personnel
to
match
the
out
of
service.
For
mechanical
and
electrical
interchangeability and to reduce the
characteristics
of
two
or
more
stock of repair parts, the same size
generators of different sizes applying
generators should be used throughout
a single load.
This combination
the system.
usually serves best to meet varied
demands at different times of the day
(1) Three of equal size.
Three
with
only
one
of
the
generators
generators of equal size, each with a
supplying the demand at any one time.
capacity just greater than two-thirds
of the maximum demand of the load, may
(3) Two of equal size.
Two
be
used.
This
combination
of
generators of equal size, each with a
generators provides slightly more than
capacity just greater than the maximum
100 percent more generating capacity
demand of the load, may be used. This
than the load and allows for one
combination of generators provides 100
machine to be out of operation without
percent more generator capacity than
affecting service during the peakload
the load and allows for one machine to
periods.
This
combination
is
be out of operation without affecting
reasonably
flexible
and
quite
the service during peakload periods.
efficient.
It allows for an increase
This combination is rather inflexible
in load of 33-1/3 percent without
and inefficient.
Since the peakload
preventing the performance of major
occurs during a small portion of the
maintenance and repair work on one of
day, the machines must operate at
the
machines
during
the
peakload
halfload or less most of the time.
periods.
During light-load periods,
This combination may be advantageous
the machines operate at approximately
when space is allotted for a third
half-load, which lowers the efficiency
unit, providing a large increase of
somewhat.
Overall efficiency of the
the load is expected to occur later.
plant
is
lower
than
for
the
11. GENERATORS AVAILABLE
combination described in (2) below and
greater than that described in (3).
This combination is preferred for
Table
4
shows
the
family
of
loads expected to grow slowly in
generators available for theater of
maximum demand.
operations installations.
The 15 KW
is
perhaps
the
most
widely
used
(2) Three of varying size. Three
because of its versatility and its
generators can be used, with one just
capability of transportation by a 2-
larger than the maximum demand and the
1/2 ton truck.
others about 60 and 40 percent of the
12. GENERATOR FIELD PROBLEMS
size
of
the
largest
machine,
respectively.
This combination of
generators provides 100 percent more
The following are examples of the
generating capacity than the load and
types of problems involving the use of
allows any one machine to be out of
generators which may be encountered in
operation without affecting peakload
the field.
performance.
This combination allows
efficient operation, since only one
a. Example
1.
The
commanding
generator is required at a time and
officer
of
a
unit
has
requested
the proper generator can be chosen to
that
his
tent
be
equipped
with
meet the varying loads.
Normally,
an
electric
light.
Your
task
each unit runs for approximately equal
1-11
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