Many industrial machines and equipments are working on Three Phase AC Voltage Scanner. To prevent or control the damage against one of the phase failure or phase reversal, the protection device such as our LVS-3 must be employed in the system. Our manufactured model LVS-3, measures and displays three incoming phases, monitors the status of their levels. It also, compares with the preset high and low limits and gives alarm (trip contact) in case the levels are abnormally high or low. Moreover, it gives the alarm output, in case of phase failure and phase reversal.