Abstract: In this paper, we propose a new Auto Transfer Switch (ATS) using only the magnetic contactor without relay unlike conventional ATS. In order to design the ATS, a triple power source is used such as a first power source, a second power source and an emergency generator power source. First power operation design conditions, second power operation design conditions and emergency generator design conditions are presented. The designed ATS did not use any relays and it was implemented with only the magnetic contactor. In the automatic mode, it is possible to solve the short circuit accident due to the phase difference between the different Distribution Line (D/L), and to solve the trip problem due to the neutral line problem between each D/L.
Keywords: Auto transfer switch (ATS), Magnetic contactor, Distribution line (D/L), Emergency generator. Short circuit.