Static Transfer
A static transfer switch (STS) — also marketed as ATS in single-phase low-current contexts — uses solid-state semiconductors (typically SCR thyristor pairs) to transfer the load from a preferred AC source to an alternate source on detection of a fault on the preferred. Because the transfer is solid-state, the cut-over takes milliseconds rather than the tens of milliseconds typical of mechanical contactor-based ATS units.
For Riello’s Multi-Switch ATS product, the page cites IEEE 1100-1999 (a 21 ms holdup specification across 100–240 VAC) and ITIC-CBEMA-table-compliant transfer time. STS units are commonly placed downstream of two parallel UPS strings to give a single rack output that can survive the failure of either UPS.
Implemented by
- Multi-Switch ATS — single-phase 30 A static transfer switch
Connections
- Multi-Switch ATS — implements_feature, source: https://standbysystems.co.za/ups_products/multi-switch-ats/
- Parallel Redundancy — relates (downstream of parallel UPS strings), source_status: inferred