Eaton Power Xpert 9395C Installation And Operation Manual

Eaton Power Xpert 9395C UPS Installation and Operation Manual 164000821—Rev 06 91If the UPS transfers to Bypass mode from Normal mode due to any reason other than operator intervention,the UPS automatically attempts to transfer back to Normal mode (up to three times within a ten minute period).The fourth transfer locks the critical load to the bypass source and requires operator intervention to transfer.66..22..55 BBaatttteerryy MMooddeeThe UPS automatically transfers to Battery mode if a utility power outage occurs, or if the utility power does notconform to specified parameters. In Battery mode, the battery provides emergency DC power that the inverterconverts to AC power.Figure 56 shows the path of electrical power through the UPS system when operating in Battery mode.During a utility power failure, the rectifier no longer has an AC utility source from which to supply the DC outputcurrent required to support the inverter. The input contactor K1 opens and the battery instantaneously suppliesenergy to the battery converter. The converter boosts the voltage so that the inverter can support thecustomer's load without interruption. The opening of contactor K1 prevents system voltages from bleedingbackwards through the static switch and rectifier snubber components and re-entering the input source.If the input power fails to return or is not within the acceptance windows required for normal operation, thebattery continues discharging until a DC voltage level is reached where the inverter output can no longersupport the connected loads. When this event occurs, the UPS issues another set of audible and visual alarmsindicating SHUTDOWN IMMINENT. Unless the rectifier has a valid AC input soon, the battery continuesdischarging until a DC voltage level is reached where the inverter output can no longer support the sharedloads. If the bypass source is available, the UPS transfers to bypass instead of shutting down.If at any time during the battery discharge the input power becomes available again, contactor K1 closes andthe rectifier begins to supply DC current to the converter and inverter. At this point, the unit returns to Normalmode. Depending on the total load and the duration of the battery discharge, battery current limit alarms maybe seen for a short time due to the current required to recharge the battery.Figure 56. Path of Current Through the UPS in Battery ModeStaticSwitchretrevnIreifitceRK1BatteryConverterBatteryBatteryBreakerMain Power FlowTrickle CurrentEnergizedDe-EnergizedClosedOpenBreakers ContactorsBypass InputRectifierInput OutputUnderstanding UPS Operation