Control system and method for switching and intercepting power supplies

A method of controlling a power supply switching and intercepting control system including a central processor 130 for producing signals for controlling switching operations of a power switching section 140 for switching main and backup power supplies A and B, and a power intercepting section 150 for performing trip and return operations with respect to the input power supplies, phase signal input sections 122 and 122′ for inputting phase difference information of the main and backup power supplies to the central processor, voltage signal input sections 126 and 126′ for inputting signals corresponding to voltage values of the respective power supplies to the central processor, and reference voltage generating sections 124 and 124′ for generating and inputting reference voltages to the central processor and the voltage signal input sections, the method comprising the steps of:

• producing an intercepting control signal to the power intercepting section in case that the main power supply is supplied with its voltage below a predetermined lower limit value Vr−Vo for an undervoltage trip delay time t0;
• producing to the power switching section a switching control signal for switchover to the backup power supply after a first predetermined delay time tB in case that the undervoltage is supplied due to a failure of the main power supply;
• producing a restoring control signal to the power intercepting section after a predetermined return time tr elapses after the power intercepting section produces the intercepting control signal;
• producing again to the power switching section a switching control signal for switchover to the main power supply after a second predetermined delay time tA after the power switching section produces the switching control signal for switchover to the backup power supply;
• producing an intercepting control signal to the power intercepting section in case that the main power supply is supplied with its voltage above a predetermined upper limit value Vr+Vo′ for an overvoltage trip delay time t0′;
• and
• producing again a restoring control signal to the power intercepting section after a second return time tr′ elapses after the power intercepting section produces the overvoltage intercepting control signal;
• wherein the power switching control signal for switchover to the main power supply is performed at a time point where the phase difference between the main and backup power supplies that is detected from the phase difference signal inputted from the phase signal input sections is within a predetermined range x;
• the trip delay times t0 and t0′, the return times tr and tr′, the first and second delay times tB and tA, the upper and lower limit values Vr-V0 and Vr+Vo′ and the predetermined range x can be adjusted by a determining section 300;
• and optimum parameters for characteristics of loads and system can be selected by inputting values adjusted by the determining section to the central processor;
• whereby the loads are prevented from being adversely affected by the supply of the overvoltage or the undervoltage, and the loads and system are prevented from being adversely affected by a serge current occurring during the power switching operation or an ark occurring from the power switching section.