INTRODUCTION
As the zeal for change over on public power supply and
stand-by generator increases, Engineers have researched deep into the different
ways and methods of achieving power change-over both manual and automatic
types.
It may not be considered a serious issue in some places where
supply is up-to 90% constant or where intermittent outage causes no great
damage. However, places like the business centers, industrial areas, and even
cold rooms need almost 100% power supply. So in this case there is need to
provide a stand-by power supply in the event of power outage. The important
thing is to make sure an effective stand-by power supply which is constant and
reliable is provided to eliminate the problem of long time outage.
Before, this time, changeovers are operated manually, there
by making it difficult for power continuity without a time wastage. This is
because an operator must always be available at any point in time. This
manually operated change-over switch has two switchable positions-(main and
generator) an arm is also provided from where the operator can have access to
the switching. Here, the effectiveness, i.e. the fastness of the switching
anytime power needs to be changed is slow, and largely depends on the operator,
which means that the system will be in-effective whenever the operator is not
available.
The
second generation of change over switch were made semi-automatic in which the
main power supply directly powers the contactors. This arrangement is made in
such a way that if the main power supply fails, the contactors will all drop,
leaving the supply to the generator position. The effectiveness of the system
will now depend on the operator to start the generator on time.
The main problem suffered by the manual and semi-automatic
systems is that the operator must have to be continuously be on duty for it to
be very effective. This depends on fully closed loop system to operate.
With more research by the scientists and engineers to improve
on the earlier ones, the present day technology has made it possible for the
change over switch to be more effective and fast with less labour more
improvements has be made in terms of number of designs, using the closed loop
system at feed back control. Some also use comparators, logic circuits and
electronics timers to achieve the task.
The design of this project is in such
a way that control or switching is done without any noticeable sign. It uses a
combination of comparators digital switches (relays) and electromagnetic
switches to achieve a very fast and effective change-over in the case of power
failure. This type of switch does not depend on any operator to function well.
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