Eaton Power Xpert 9395P-1100/1100 Installation And Operation Manual

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118 Eaton® Power Xpert® 9395P-1200 Installation and Operation Manual 164000500—Rev 1166..22..66 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 65 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 either bucks or boosts the voltage so that the inverter cansupport the customer's load without interruption. If bypass is common with the rectifier input, the backfeedprotection contactor K5 also opens. The opening of contactors K1 and K5 prevent system voltages frombleeding backwards through the static switch and rectifier snubber components and re-entering the inputsource.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 output can be supportedfor only two minutes before the output of the system shuts down. If the bypass source is available, the UPStransfers to bypass instead of shutting down.If at any time during the battery discharge the input power becomes available again, contactors K1 and K5 closeand the rectifier begins to supply DC current to the converter and inverter. At this point, the unit returns toOnline mode. Depending on the total load and the duration of the battery discharge, battery current limit alarmsmay be seen for a short time due to the current required to recharge the battery.Figure 65. Path of Current Through the UPS in Battery ModeK1 K3K5K1 K3K2Main Power FlowTrickle CurrentEnergizedDe-EnergizedContactorsBreakersBypass InputRectifierInputInputBreaker(CB1)BatteryBreakerOutputClosedOpenRectifier InverterStaticSwitchBatteryConverterBatteryNOTE On a UPS configured as an IOM, the bypass input, static switch, bypass breaker (CB4), and K5 are not present.NOTE On a UPS configured with a Continuous Static Switch (CSS), bypass breaker (CB4) is not present.Understanding UPS Operation