Eaton 93PR - Stored Energy and Battery Mode; Figure 2-11: Path of Current through the UPS in Battery Mode

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Eaton 93PR 60-1200 kW UPS

Installation and Operation Manual

2.2.2. Stored Energy and Battery Mode

When running normally in double conversion or ESS mode, the UPS automatically transfers to

supply the load from batteries or other stored energy source if a utility power outage occurs, or

if the utility power does not conform to specied parameters. The UPS status indicated on the

display is “On Battery”, and the UPM status is “Active”. In Battery Mode, the battery provides

emergency DC power which is converted to regulated output power by the inverter.

Figure 2-11

shows the path of electrical power through the UPS system when operating in Battery Mode.

Figure 2-11: Path of current through the UPS in Battery Mode

During a utility power failure, the rectier no longer has an AC utility source from which to supply

the DC output current required to support the inverter. The input relay K1 opens and the UPS

output is powered from batteries through the inverter. As the inverter operates uninterrupted

through the transition, the load remains supported continuously without disturbance. If the UPS

static bypass is supplied from the same source as the UPS rectier, the backfeed protection

contactor K5 also opens. The opening of K1 and K5 prevent system voltages from bleeding

backwards and re-entering the input source through the static switch or rectier.

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 a set

of audible and visual alarms indicating that the batteries are having a minimal capacity left and

a system shutdown is imminent. Unless utility power is restored, the output can be supported

for maximum 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.

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