Parallel UPS Configuration 101

In today’s world where almost everything is dependent on machines, data’s, servers, an unexpected power loss or power fluctuation even for a minute can be very damaging.  Hence, to avoid such risk in the system, a multiple UPS system is set up to ensure backup when the first power backup supply fails.

What is it?

In parallel UPS configuration, two or more UPSs’ are both electrically and mechanically connected to create a combined system with only one output where each UPS acts as a backup ready to take over the load from another UPS whenever necessary, without breaking the supply. The modern parallel UPS configuration is independent of any external switch control and is auto aligned to serve the purpose for which it is made.

There are basically two types of parallel UPS configuration systems namely Parallel Redundancy and Parallel Capacity.

  • Parallel-redundant UPS system is made up of one or more UPS modules running in parallel arrangement known as N+X. Here X stands for the number of additional UPS modules other than the first UPS module in the arrangement.
    • All UPS modules share the load and in case one of the UPS fails, the other UPS modules will fulfill the power requirement assuring there is no break in power supply. The standard number of UPS modules in Parallel-redundant UPS configuration is eight which can be maximized to ten.
    •  Parallel-redundant UPS configuration is most commonly used in places which require the highest levels of power supply.
  •  A Parallel-capacity System (N) comprises of multiple UPS working in parallel but without redundancy. It does not increase resilience but definitely is an inexpensive option than the Parallel Redundant UPS system. The capacity of this system is dependent on the total number of UPS modules used in a configuration.

The advantage of a parallel-redundant system over a parallel-capacity system is that it allows the maintenance work to be carried out without any disruption whereas; a parallel-capacity configuration has to be entirely detached. This gives the parallel redundant system an edge over the latter.


How it works?

To design a parallel UPS system, the whole system needs to be sized so as to ignore overloads in case any of the modules fail. This means that the system should be designed for higher loads thereby leaving no room for any possible mishaps and reducing potential dangers associated with overloads.


  • At times when incoming mains power supply (or generated supply) is present, each of the UPS modules in both a parallel-redundant and a parallel-capacity system will equally share the load. The same holds true when the system is operating in battery mode.


  • In case there is a fault in any of the UPS, it will be automatically disconnected and its load will be shared by other UPS modules without disrupting the power supply. Now, if another module from the system fails, the faulty modules are bypassed and the additional load is shared between the remaining UPS modules equally.


UPS installations generally rely on common main power supply for both the UPS and static bypass. It creates a big risk of power failure. Using dual input supply from two or more different sources, resolves this problem. In designing uninterrupted power backup for reliability, there is a growing trend towards parallel UPS system. This system is an ideal option where power protection is critical requirement.


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