A static inverter is designed for use with emergency lighting systems and other safety-related applications. It performs a similar role to a standard uninterruptible power supply, but provides backup for a longer time, usually either 1 or 3 hours. 

In effect, a static inverter performs in the same way as a UPS system running in Standby operating mode with the bypass supplying the load and no filtering of the mains supply. When a mains failure occurs, the static inverter switches to running off batteries.  

Static inverters must comply with the EN 50171 safety standard for Central Power Supply Systems. One of the criteria this involves is the capability to clear a final circuit fault and continue running without breaking its own circuit protection device.  

Standard UPS systems are not designed to meet EN 50171 specifications and therefore should not be used to back up emergency lighting and similar applications. However, there are specially-designed UPS for emergency applications to meet these requirements.  


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