Operating mode Description- Energy Saver System (ESS) mode Critical load is supported securely by utilitypower through the static bypass switch withdouble conversion available on-demandwith typically less than a 2 ms transitiontime, should any abnormal condition be de-tected in the utility. When operating in theESS mode, the load is protected with inher-ent surge suppression. Operating the UPSin the ESS mode increases system effi-ciency up to 99%, allowing significant sav-ings in energy losses without compromis-ing system reliabilityStored energy mode Energy is drawn from a DC backup powersource and converted to AC power by theUPS inverter. Most commonly VRLA bat-teries are introduced to the system for thispurpose, and the mode of operation iscalled the battery modeBypass mode Critical load is supported directly by utilitypower through the UPS static switch.3.2.1 Normal operating modesDuring normal UPS operation, power for the system is derived from a utility inputsource.Unit Online is displayed on the front panel, indicating that theincoming power is within voltage and frequency acceptance windows.3.2.1.1 Double conversion modeFigure6 shows the path of electrical power through the UPS system when theUPS is operating in the double conversion mode.Eaton 9PHD UPS 30–200 kW User's and installation guide© Eaton Corporation plc 2017. All rights reserved. Document ID: P-164000531 23 (127)
