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Power Efficiency

Static Transfer Switch

STS

An electronic switch that transfers a critical load between two independent power sources in under 4 milliseconds.

Unit: A / kVA

Full Definition

<p>A Static Transfer Switch (STS) uses thyristors (SCRs) to transfer a load between two synchronised AC power sources — typically the A and B feeds of a dual-bus data centre — without interruption to the IT equipment. Transfer time is typically 2–4 ms, within the hold-up capability of most server PSUs.</p><p>An STS is installed downstream of the UPS and upstream of the PDU, providing a second layer of redundancy against single-bus faults. Unlike a manual changeover switch or a bypass panel, the STS operates automatically on detecting a disturbance — overvoltage, undervoltage, frequency deviation or loss of phase.</p>

Also Known As

automatic transfer switchATSstatic bypass switch

Source Reference

IEC 62310-1; Eaton STS product series

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