Clearing confusion with UPS systems

It is widely believed that there are only two types of UPS (Uniterruptible Power Supply) systems, namely standby UPS and online UPS. These two commonly used terms do not correctly describe many of the UPS systems available. Many misunderstandings about UPS systems are cleared up when the different types of UPS topologies are properly identified. UPS topology indicates the basic nature of the UPS design. Various vendors routinely produce models with similar designs, or topologies, but with very different performance characteristics.  A variety of design approaches are used to implement UPS systems, each with distinct performance characteristics:

 

 

Practical

Power

Range

(kVA)

 

Voltage

Conditioning

 

Cost Per

VA

 

Efficiency

 

Inverter

Always

Operating

Standby

0 – 0,5

Low

Low

Very high

No

Line interactive

0,5 - 5

Design

dependent

Medium

Very high

Design

dependent

Standby-ferro

3 - 15

High

High

Low –

medium

No

Double conversion online

5 – 5 000

High

Medium

Low –

medium

Yes

Delta conversion online

5 – 5 000

High

Medium

High

Yes

 

Take Note

  • There are at least five distinct UPS system designs.
  • Each UPS system design is best suited to specific applications.
  • The basic quality of design implementation and manufactured quality are dominant in determining ultimate performance.

 

Published as: Different types of UPS systems

By N Rasmussen, Schneider Electric

Electricity+Control: January 2012 (pgs 38 – 41)