AC Power
For Business-Critical Continuity™
Liebert®
STS2 Static Transfer Switch2 
The Cornerstone of High-Availability Power Systems
The Power to Protect Your
Critical Operations 
For maximum availability applications, the Liebert Static Transfer Switch2 (STS2) provides an automatic, seamless transfer between your critical load and the outputs of two independent UPS systems in a dual-bus power configuration. If the primary UPS should fail, the switch will automatically transfer the loads to the alternate UPS.
Liebert is the market leader in dual-bus power systems, building the world’s most reliable UPS and Static Transfer Switch products. Liebert STS2 further extends our market leadership with design benefits unmatched by competitive products.
Standard Features Of The
Liebert STS2 Provide Greater
Overall Protection
Reliability:
100% rated, fuseless design.
Hot-swappable circuit breakers.
Flash memory enables firmware updates while supporting critical load.
Rack-out control/power assembly on units up to 600A to allow maintenance, service or full replacement without disrupting the critical load.
Flexibility:
Internal CANBUS protocol: high-bandwidth communication between system components via twisted-pair cables. Options can be added as simple network nodes.
Dual-lug installation bus with pem nuts for single-hand installation and “hot” torque service.
Low Total Cost Of Ownership:
Conservative design margins and excellent overload capacity.
UL listed.
Color Touch-Screen Interface
The color touch-screen LCD interface allows you to quickly check the status of the unit and identify problems. The controls of the Liebert STS2 are intuitive and simple.
The color LCD monitor is divided into three segments. In addition to a system mimic diagram, there is a Status/Alarm panel and a section dedicated to operator instructions and menus. The screen allows you to configure the unit, including the control of the preferred source, auto/manual retransfer selection, alarm notification and other system setpoints. You benefit from improved operator effectiveness, reduced training time, and less chance of operator error.
2
For units up to 600 amps, the entire power and control module can be removed as an assembly.
True Front-Access Design
All mechanical and electronic components of the Liebert STS2 are accessible from the front of the unit for installation and service—no side or rear access required.
This gives you several immediate benefits:
Greater freedom in system design. The Liebert STS2 can be placed adjacent to or in back of other equipment. It can also be placed against a wall or partition.
Simplified installation, with ample space for cable connections through top and bottom access plates.
Less floor space required for maintenance access.
Designed for maintainability, with all key components visible and accessible from the front of the unit, without shutting down the connected load.
A separate compartment for option modules provides safe and convenient field access.
True Internal Redundancy
The Liebert STS2 has tripleredundant logic. Each DSP controller is capable of working independently, and each helps monitor the other two. If one malfunctions, the other two lock it out. Each controller has power feeds from both power supplies.
The two power supplies feature true dual-bus power distribution. Both have dual inputs, one from each AC input source. All power connections have diode protection, so that internal or external faults cannot propagate. The result is a rugged, fault-resilient package that is optimized for realworld applications.
One-Line Diagram
|
Source 1 |
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Source 2 |
|
CB1 |
|
CB2 |
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|
K1 |
|
K2 |
|
K2 K3 |
CB4 |
CB3 |
K1 K3 |
CB5 |
System Output
3
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