Mains supply with battery back-up - switched in by relay stages to maintain continuity esp. in hospital

摘要

An electrical power supply system has a mains supply (1) and an emergency supply (2) in the form of a battery (3) powered a.c. inverter (4). Load circuits (5) are connected to the mains via relays (H1, H2) and a transformer (T) that provides isolation as required in hospital systems. The back-up supply is connected via a pair of relays (N1, N2) with output lines commoned onto the mains supply lines. As the back-up supply is switched in, the mains is switched out by the action of links (12, 13). ADVANTAGE - High level of functional security, even if fault arises on switching elements, good chance of switch-over remains.