File Name: design and construction of an automatic changeover switch .zip
Power failure or outage in general does not promote development to public and private sector. The investors do not feel secure to come into a country with constant or frequent power failure. These limit the development of industries.
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However, if the starting of the generator is automatically done by a relay which switches the battery voltage to ignition coil of the generator while the main power relay switches the load to either public supply or generator, the down time would greatly be reduce thereby maintaining the tempo of production in such industries.
A manual change-over switch consists of a manual change over switch box, switch gear box and cutout fuse or the connector fuse . The approach used in this work is the modular approach where the overall design is first broken into functional blocks as shown in the above block diagram. The 3-phase automatic change-over switch has been divided into eight 8 blocks as shown in Fig.
Each of these blocks carries out a specific function in the entire system as shown by the interconnections between the blocks. The Public Power Supply has a nominal three phase or phase-to-phase voltage level of a. The Circuit Power Supply is tapped from the public power Supply and rectified to power the circuitry. The main function of the circuit power supply is to convert a. The first stage makes full wave rectification from the a. The rectified d.
Finally, appropriate voltage regulators LM78XX are then selected to keep the d. Voltage RegulatorIn this design, and regulators are used, which can provide up to 2A guaranteed with only 1. Input voltage must be around 15V, otherwise the regulator temperature will increase as input voltage increases . If the two voltage levels are equal, there will be no output from the sensor but if a reasonable discrepancy is experienced, an output will be obtained from the sensor.
The comparator stage is used to sense when the public power supply voltage has dropped below a certain preset level. The input public power supply voltage is converted to d. The unregulated voltage varies as the public supply input varies. Remember, V a. It is being taken as dangerously low voltage for appliances meant to operate with a nominal voltage of V a. At the 3-phase power supply V a. Looking at Fig.
Assuming a maximum adjustable reference voltage of 2. As the Public Power Supply input drops below 1.
As the output goes above 1. A base resistor; R B is required to ensure perfect switching of the transistor in saturation . Physical size and pin arrangement: A relay is chose based on the existing PCB to ensure that its dimensions and pin arrangement are suitable for the designed project. Coil Voltage: The relay coil voltage rating and resistance were taken into consideration.
Coil Resistance: The circuit must be able to supply the current required by the relay coil. Also, the logic stage implemented in section 4.
The result clearly shows the relationship between the input, regulated and the unregulated voltage levels. The result in Table 2 shows a deviation between the practical and calculated values. This is attributed to losses and stray capacitances in the implemented circuit.
However, these losses do not affect the performance of the switch. Table 3 shows the switching sequence of the compared voltages for 3-input AND gate The sequence 1,1,1 produces an output of '1'. This when coupled to the BC transistors turns them 'ON' thus initiating a switch via the relay. All other sequences from the table are those at which the compared voltages has no or negligible difference.
When these sequences with '0' or 'OFF' are coupled to the transistors, no changeover is initiated thus the circuit only monitors. The system worked according to specification by monitoring phase failure and under-voltage thereby changing over to the alternative power supply.
This automatic electronic system operates without human intervention hence the sluggishness of manual operation is eliminated and production downtime reduced to the barest minimum thereby reducing production losses and costs. Calculated Dif. BetweenV R2 V C Input voltage: This is an a. Related Papers. Development of A Cost Effective 2.
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It is designed in several blocks all combined to from one functional unit. The output of the BCD — Decimal decoder is used to select the phase in priority through a transistor driver stage and electromagnetic relay that activates contactors. The least prioritized phase is the Gen set which contains a circuitry that automatically starts and stops the Gen set. The system is realized with TTL chips market. LEDs and AC panel lamps are used to indicate the status of the system while a manual switch is used to demonstrate the mode of operation of the system. Power control and automation is a part of this field which is applied in virtually anywhere electrical power is used, generated or transmitted. Manual power change-over switches have been in existence and in different forms and shapes.
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Most industrial and commercial processes are dependent on electrical power. In the event of power interruptions, the change-over from power supplied by a public utility to a generator is usually performed manually, often resulting in wasted time. Moreover, machine damage sometimes occurs because of human errors.
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It is designed in several blocks all combined to from one functional unit. The output of the BCD — Decimal decoder is used to select the phase in priority through a transistor driver stage and electromagnetic relay that activates contactors. The least prioritized phase is the Gen set which contains a circuitry that automatically starts and stops the Gen set. The system is realized with TTL chips market. LEDs and AC panel lamps are used to indicate the status of the system while a manual switch is used to demonstrate the mode of operation of the system. Approval page ii.
Старик утратил к нему всякий интерес, прихожане встали и запели гимн. Ноги у него свело судорогой. Хорошо бы их вытянуть.
- Ему не стоило напоминать о поразительной способности Мидж Милкен предчувствовать беду. - Мидж, - взмолился он, - я знаю, что ты терпеть не можешь Стратмора, но… - Это не имеет никакого значения! - вспылила. - Первым делом нам нужно убедиться, что Стратмор действительно обошел систему Сквозь строй. А потом мы позвоним директору. - Замечательно.