Date Added: Apr 2010
When UPS application engineers get into a technical discussion eventually the topic of conversation will turn to how big does a genset need to be for a UPS system? When that happens many 'rules-of-thumb1' are expressed with very few, if any, caveats. Unlike many topics in the UPS world the subject of generator sizing has become more complicated with time as UPS topology has changed the nature of the rectifier-charger interface with the upstream power supply, be that mains or standby-generator - but the rules-of-thumb have persisted. This paper will attempt to show that rules-of thumb are hardly ever right and are increasingly misguided.