Battery Charger Efficiency Optimization

Energy can be saved in a telephone office by controlling each power plant rectifier so that its load is close to the value for which efficiency is highest. An example is given where energy savings of over $1,400 per year result when current sharing is added to a group of five 800 amp rectifiers (based on electricity that costs 5 cents per kwh). Previously these rectifiers ran mostly at full load or at no load. The amount of savings depends on how the total plant load varies with time, on how the rectifier efficiency varies with load, on the number of spare rectifiers and on how the rectifiers are controlled to share the load. How to calculate the exact energy loss per year for virtually any rectifier plant is explained in a step-by-step procedure. A detailed example is given. The procedure is used to present the yearly energy savings for eight typical combinations of rectifier type, plant load variation pattern and energy saving control. General conclusions are drawn about the situations where is should be practical to current share and where it is worth considering the turnoff of unused spares.