UPS specifications & performance

Many UPS systems do not perform as their purchasers intended leading to unreliability, expensive investigation of deficiencies and even litigation. The technical reasons are often a failure to appreciate and incorporate in the tender the system requirements: classically the nature of the typical nonlinear load causes many problems. For example, the paper shows how these waveforms can be defined and interpreted for performance against UPS specifications. UPS are needed where the loss of power can cause loss greater than the UPS cost, where safety and the law require a high integrity of supply, and where wind/solar installations need energy storage for continuity of supply. Some of these applications can stand short discontinuities whilst contactors operate or even longer for stator engine driven generators. In this review the classical UPS is examined with the inverter feeding the load and a static bypass is always available