Distributed Bypass Advantages for UPS Systems

Distributed Bypass systems add no additional cost as there is when a centralized bypass switch is required.  The integral bypass switch is built into each UPS, and so does expand the system footprint.  The Tie cabinet does not need any intelligence. It is simple, reliable, and vendor-independent.  In an N+1 configuration, the distributed bypass design provides redundancy in the event of a failed static switch.


The argument for centralized bypass is simply that simplicity = reliability. The contrary truth is made evident when one considers that a parallel UPS system is more complex than a single large UPS, though parallel UPS systems are commonly designed to provide redundancy and therefore reliability. Likewise, distributed bypass adds a very simple device to each static switch circuit (a contactor) indeed making the bypass path only marginally more complex, yet far more reliable as a result.

Other considerations are:

  • Increased cost: The centralized Static Switch would have to be purchased in addition to the UPS.
  • Increased footprint: The centralized SS would be in a dedicated stand-alone cabinet in addition to the rest of the system
  • Dependence on a single switch, breaker, and motor operator if the switch is momentary, introducing a single point of


In the G9000, the hybrid bypass switch is incorporated in each UPS module. This simple circuit incorporates a thyristor/contactor switch that adds minimum complexity in exchange for greatly increasing each units bypass MTBF to 3,000,000 hrs.