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.

1.1 BACK GROUND

The background to this project work is traced to the in tense demand of the populace and industries, residential homes, and many more demand for change of power supply switch for effective and continuity of power supply without a notice interruption or delay in such process to any alternative supply if the main supply goes off.

Earlier to this time, such process is manually operated or not in used at all. The manual type which is always strenuous and time delayed was a little bit useful but not to a satisfactorily level. More level and expenses are always