PQI’s challenge was to improve transformer efficiency & reduce the subsystems’ zero-sequence impedances
PQI’s challenge was to improve transformer efficiency & reduce the subsystems’ zero-sequence impedances
2 PagesCASE STUDY Johns Hopkins University School of Medicine, Preclinical Building Facility Description The Preclinical Building is located in a relatively small four- story building that was completed in 1981. This preclinical building consists mainly of small medical offices. When compared to the facility’s combined 277-volt lighting and 480-volt HVAC loads, its 120-volt office loads actually consume more energy. This load group’s harmonic current-generating switch-mode power supplies create the facility’s best energy-saving opportunity. Existing Conditions • Two large inefficient pre-NEMA TP 1 distribution transformers • 14.9% daytime loading of the transformers • Unacceptable levels of positive-, negative- and zero- sequence harmonic currents • Unacceptable
