Abstract: A control system for switching and intercepting power supplies which can reduce the generation of arc during the switching operation of main and backup power supplies and adjust the delay time required for the switchover of the power supplies. The control system includes a phase signal input section for detecting phases of the main and backup power supplies, a reference voltage generating section for generating a reference voltage, a supply voltage signal input section for detecting voltages of the main and backup power supplies, and a control section for receiving and processing output signals of the phase detecting section, reference voltage generating section, and supply voltage detecting section.