Powerware 650825 kVA operation manual Battery Mode

UNDERSTANDING UPS OPERATION

The internal bypass is comprised of a solid−state, silicon−controlled rectifier (SCR) static switch (SSW), a motorized wraparound bypass breaker CB4, and a backfeed protection contactor K5. The static switch is rated as a momentary−duty device that is used instantaneously anytime the inverter is unable to support the applied load. The static switch is wired in series with the backfeed protection contactor, and CB4 is wired in parallel with this combination. Together they are wired in parallel with the rectifier and inverter.

The static switch, being an electronically−controlled device, can be turned on immediately to pick up the load from the inverter while bypass breaker CB4 closes and inverter output contactor K3 opens to isolate the inverter. When breaker CB4 closes, the static switch stops conducting. The backfeed protection contactor is normally always closed, ready to support the static switch unless the bypass input source becomes unavailable.

If 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.

6.2.4Battery Mode

The UPS automatically transfers to Battery mode if a utility power outage occurs, or if the utility power does not conform to specified parameters. In Battery mode, the battery provides emergency DC power that the inverter converts to AC power.

Figure 6-4shows 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 output current required to support the inverter. The input contactor K1 opens and the battery instantaneously supplies energy to the battery converter. The converter either bucks or boosts the voltage so that the inverter can support the customer’s load without interruption. If bypass is common with the rectifier input, the backfeed protection contactor K5 also opens. The opening of contactors K1 and K5 prevent system voltages from bleeding backwards 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, the battery continues discharging until a DC voltage level is reached where the inverter output can no longer support the connected loads. When this event occurs, the UPS issues another set of audible and visual alarms indicating SHUTDOWN IMMINENT. Unless the rectifier has a valid AC input soon, the output can be supported for only two minutes before the output of the system shuts down. 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, contactors K1 and K5 close and the rectifier begins to supply DC current to the converter and inverter. At this point, the unit returns to Normal mode. Depending on the total load and the duration of the battery discharge, battery current limit alarms may be seen for a short time due to the current required to recharge the battery.

EATON Powerware® 9395 UPS (650–825 kVA) Installation and Operation Manual S 164201725 Rev 2 www.powerware.com 6−5