In high-availability designs, critical loads are often fed from two independent power paths. Load Bus Synchronization (LBS) is the feature that keeps those two paths in step so equipment can switch between them without disturbance.

What LBS actually does

LBS keeps the output buses of two separate UPS systems phase-aligned. When dual-corded equipment, or a static transfer switch (STS), moves the load from one bus to the other, the two sources are already synchronized – supporting clean transfer conditions when the complete STS / dual-bus design is properly configured. LBS is a coordination feature: it aligns phase between independent systems. It does not distribute load.

LBS vs parallel operation

These two are often confused, but they solve different problems:

Parallel operationLBS (Load Bus Synchronization)
PurposeShare load / add redundancy on one busPhase-align two separate buses
TopologyMultiple UPS, one common outputTwo independent UPS systems / buses
What it managesLoad distribution and N+X redundancyOutput phase coordination for transfer
Typical useCapacity and redundancy on a single pathDual-bus / 2N, STS-fed dual-corded loads

In short: parallel operation distributes the load across units on one bus; LBS synchronizes two otherwise independent buses so loads can move between them cleanly. A design can use both – parallel units on each bus, with LBS between the two buses.

When do you need LBS?

  • Dual-bus / 2N architectures where every critical load has two independent power feeds.
  • STS-fed dual-corded equipment that must transfer between sources without interruption.
  • High-availability data centers and critical facilities that cannot tolerate transfer disturbances.

LBS on ATENCO UPS

ATENCO supports LBS on selected three-phase UPS platforms designed for coordinated multi-system architectures – for example the RM33E 40 to 50 kVA models include an LBS port for dual-bus synchronization, and larger three-phase and modular TM66E platforms support coordinated architectures by project review. Parallel operation and N+X redundancy are configured separately. See also single-phase vs three-phase architecture.

Project note: Final LBS, parallel, STS, bypass and source-synchronization design should be confirmed against the exact UPS series, site single-line diagram, load type, redundancy target and commissioning procedure.

LBS, parallel operation and redundancy are configured per project. Availability and port options vary by series and model; confirm against the specific UPS and the dual-bus design.

Key takeaways

  • LBS = Load Bus Synchronization – it phase-aligns two independent UPS output buses.
  • It is a coordination feature for dual-bus / 2N and STS-fed dual-corded loads.
  • Parallel operation distributes load on one bus; LBS synchronizes two separate buses.
  • ATENCO supports LBS on selected three-phase platforms (e.g. RM33E 40-50 kVA, TM66E modular) by project review.