Automatic load switching board

Automatic load switching board (ALSB) is used to reconnect the load to a source of power by automatically switching to a second (backup) input when power is lost at the first (main) input. Normally, the switchboard is reset automatically when the main source of power is restored (priority of the first input). The main input is typically a stationary power mains Un = 380 V, f = 50 Hz. The backup input can be a stationary power mains or a diesel generator. ALSBs are widely used at industrial and civil engineering sites, cellular communication stations, etc., and are also used to supply power during scheduled maintenance and repair work.

State-of-the-art electronic devices are used to automate the switchboard. The most frequently used set of control circuits is a full-function phase-monitoring relay; special controllers are specified less often. These devices control power elements — contactors, breakers, or circuit breakers with servo drives.