Static Transfer Switches

A Static Transfer Switch (STS) is a solid-state electrical device that ensures continuous power to critical loads by seamlessly switching between two independent AC power sources without interrupting the load.Unlike traditional Automatic Transfer Switches (ATS) that rely on slow, mechanical moving parts, an STS utilizes Silicon-Controlled Rectifiers (SCRs) or thyristors to manage the power path. This solid-state architecture allows the STS to detect upstream power anomalies in under 1 millisecond and execute a "break-before-make" transfer, typically in less than a quarter-cycle (under 5ms). Because this transfer happens far faster than the hold-up time of standard power supplies, sensitive IT equipment, medical devices, and industrial automation networks remain fully operational without rebooting or experiencing data loss.

An Automatic Transfer Switch (ATS) uses mechanical relays or contactors to switch between primary utility power and backup generators, which takes tens to hundreds of milliseconds and will cause sensitive IT equipment to reboot. A Static Transfer Switch (STS) is a solid-state device utilizing Thyristors/SCRs to switch between two synchronized, high-quality power sources (like two UPS systems). Because it has no moving parts, the STS detects faults in <1ms and transfers the load in a fraction of an electrical cycle, usually under 4 millisecond (ms), keeping critical equipment running truly uninterrupted.

STATIC POWER STS units utilize a digital detection algorithm that identifies a source anomaly in under 1 millisecond. For synchronous sources, the solid-state SCRs execute a complete break-before-make zero-current transfer in less than a quarter-cycle (typically <4ms). If the sources are asynchronous, the STS employs intelligent algorithms to safely manage the transfer time (up to a half-cycle) to prevent dangerous inrush currents when transformers or motors are present.

With a high MTBF (>800,000 hours), our STS variants require minimal maintenance. While solid-state architecture inherently eliminates mechanical wear and requires less maintenance, our high-availability models are designed for true concurrent maintainability. Models like the iRack B-Series and iDUAL feature integrated maintenance bypasses with overlapping CAM switches and hot-swappable power modules. This allows technicians to fully isolate, test, or swap the entire solid-state switching block without dropping power to the critical downstream load.

Our high-availability models are designed for concurrent maintainability. They feature an integrated maintenance bypass utilizing mechanically interlocked circuit breakers or overlapping CAM switches. This enables technicians to securely route power around the solid-state switching block. For our rack-mount models like the B-Series and iDUAL, the active power module is entirely hot-socket field replaceable, allowing rapid servicing without load interruption.

Fuseless STS units, such as our iMAX series, are essential in heavy industrial sites, airports, and large data centers where extreme fault currents are possible. These ruggedized units replace internal fuses with high-capacity circuit breakers, allowing the STS to safely ride through and clear massive short circuits (up to 36kA for 1 cycle on the iMAX G) without requiring physical fuse replacements after an event.

In mission-critical environments like data centers or multi-speciality hospitals, an STS prevents catastrophic data loss and keeps life-saving equipment online during upstream source failures. By executing sub-cycle, phase-synced transfers between redundant power paths (like two UPS systems), an STS also ensures servers and medical imaging machines never experience the voltage dips typical of mechanical ATS units, preventing dangerous reboot cycles and equipment damage.