ExcelTech MX‑5‑S‑I‑6‑4 6 kVA Static Transfer Switch for Data Center PLC Modules
The ExcelTech MX‑5‑S‑I‑6‑4 is a high‑reliability static transfer switch (STS) designed to provide redundant AC power to critical loads such as PLC racks, servers, and industrial controllers. Rated at 6 kVA (6000 VA), it accepts two independent AC input sources (preferably from different UPS feeds or utility lines) and seamlessly transfers the load to the healthy source within 4‑8 milliseconds if the primary source fails. The STS uses IGBTs in anti‑parallel configuration, ensuring no mechanical wear and virtually infinite switching life.
Input/Output Electrical Ratings
Nominal voltage: 120/208 V or 230/400 V (selectable via software). Frequency: 50/60 Hz ±5%. Maximum continuous current: 28 A per phase (at 208 V). Input configuration: dual independent 3‑wire plus ground (single phase) or 4‑wire plus ground (three‑phase, split phase). Output: single output bus. Overload capability: 125% for 10 minutes, 150% for 30 seconds (subject to heat sink temperature). Crest factor: up to 3:1 for non‑linear loads. Efficiency: 98.5% at full load.
Transfer Mechanism and Timing
The static switch monitors both inputs for voltage, frequency, and waveform distortion (THD<5% acceptable). Transfer decision is made by a digital signal processor (DSP). Transfer time: less than 1/4 cycle (4 ms for 60 Hz, 5 ms for 50 Hz) for asynchronous sources; for synchronous sources (phase locked), transfer break time is <2 ms. The STS also features “fast transfer” mode that forces transfer when voltage drops below 85% of nominal. An optional “make‑before‑break” mode is available for loads that tolerate a short paralleling (2 ms overlap) but requires sources to be in phase.
User Interface and Monitoring
A backlit LCD display shows source status, voltage, current, active power, and event logs. LED indicators: Source 1 active, Source 2 active, alarm, bypass active. Communication: RS‑232, RS‑485 (Modbus RTU), and Ethernet (Modbus TCP/SNMP) via optional card. The STS can be integrated with data centre PLC modules to automatically start generators or send alerts. Dry contact relays are provided for remote indication of transfer, source failure, and general alarm.
Physical and Environmental
The MX‑5‑S‑I‑6‑4 is packaged in a 2U (88 mm) high, 19‑inch rackmount enclosure. Depth: 350 mm, weight 8 kg. Cooling: front‑to‑rear airflow with two low‑noise fans (speed controlled). Operating temperature: 0‑45 °C (derate 2% per °C up to 50 °C). Storage: -20‑70 °C. Humidity: 5‑95% non‑condensing. Safety compliance: UL 62368‑1, EN 62368‑1, CE. EMC: EN 55022 Class A.
Built‑in Maintenance Bypass
The STS includes a manual maintenance bypass (make‑before‑break rotary switch) that isolates the static transfer module for servicing while maintaining load power. When engaged, the load is directly connected to either source 1 or source 2 via relay contacts. This bypass also serves as an emergency backup if static electronics fail. The unit allows “hot swap” of control logic boards without power interruption.
Applications in PLC Control Systems
Ideal for redundant power supply to OMRON, Siemens, Rockwell PLC racks, distributed I/O, and industrial PCs. By installing an STS, the PLC system remains operational during single power source failure, preventing production stops. The fast transfer time (4 ms) is well within the hold‑up time of typical industrial power supplies (20‑30 ms), making the transfer imperceptible to the load.
