This series control cabinet phase AC voltage is rectified by a step-down transformer, and then by individual (three phase) bridge rectifier unit obtains DC 220V voltage. The entire control cabinet by the automatic air switch, rectifier transformer, rectifier unit, DC contactors and other major components; circuit is provided with a short-circuit and overvoltage protection devices and other protective devices; has a simple structure, small size, light weight, reliable operation, easy maintenance and so on.