Static transfer switch [/ˈstætɪk ˈtrænsfər ˈswɪʧ/] n - A static transfer switch (STS) chooses between two independent power feeds for a single load and passes between them in milliseconds, by solid-state thyristors rather than mechanical contacts. It is how a piece of equipment with but one power cord still partakes of two power paths.

Here it differs from the Automatic transfer switch, which is mechanical, switches in seconds, and works at building scale between utility and the The Standby Engine.

Of Its Station

Two independent paths (each with its own Uninterruptible power supply, Power distribution unit, and Busway distribution) feed the STS, and the STS keeps the healthy one. This is the practical means of granting single-corded equipment the benefit of a 2N design from Redundancy topologies, though the equipment itself is not dual-corded.

Most modern servers are dual-corded and carry their own internal transfer logic across two power supplies, so a standalone STS is reserved for legacy or single-corded gear, or else set upstream of a whole rack. Either way it depends upon the two feeds sharing a common Grounding and bonding reference, lest the transfer create a fault.

Part of The Engines of the Hall.