Design and construction of three-way single phase automation transfer switch.
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In an era where the harnessing of variable renewables has gained momentum to fight against climate change and long power outages, the efficient switching devices capable of interchanging between different sources of power quickly and automatically must be given the desired attention. The existing three-way automatic transfer switches experience two common problems: slow switching speed and damaging of the electromagnetic relays by arcs encountered during their transition from one source to another. It is from this background that we proposed using a hybrid relay switching technique to overcome the damaging of contacts of the electromagnetic relay and high power loss in the solid-state silicon AC switches. This technical strategy reduces wastage of power and increases load and relay reliability. The other issue of slow switching speed is solved by reducing the delays in the control algorithm and choosing components with a higher-speed response. The project started with designing the hardware of the new system, and software needed to achieve the objectives of the research. The system designing was divided into switching units, voltage transducer units, control unit, and display unit. The switching units consist of the SRD-05VDC-SL-C electromagnetic relays and triacs (BTAL2-600B). The control unit is made up of the ATMega328p microcontroller on the Arduino Uno. The display unit is made up of blue, yellow, and green light-emitting diodes. The HI-Link HLK-PM01 AC-DC 220V to 5V Step-Down Power Supply Module is the voltage sensing unit for all three power sources. The Proteus software version 8.8 was employed to run the simulation, and Arduino IDE software to help in compiling the code. After simulating with Proteus software, we built the prototype of the switch and integrated the hardware and software algorithm. The constructed prototype was tested using a 7 W LED bulb as the load and AC power sources with voltages that lie in the scope. The prototype has a very quick switching response of 20ms, prioritizes grid electricity with the alternative energy source as the second option, and the diesel generator as the last option. It also eliminates any possibility of arcs. However, certain challenges were encountered along the way, some of which were solved. The issue of reverse current was overcome by connecting diodes where it was discovered. We recommend that a more advanced switching design capable of handling a bigger load is made with even an option of switching between more than three power sources.