Powerware 10001100 kVA Battery Mode, Path of Current Through the UPS in Bypass 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.

Bypass Input

Bypass

Breaker

(CB4)

Static

Rectifier Input

Input

Breaker

(CB1

Rectifier

K1

Switch

K5

Inverter

K3

Output

Breakers Contactors

Closed

Open

Battery

Converter

K2

Battery

Breaker

Battery

Main Power Flow

Trickle Current

Energized

De−Energized

Figure 6-3. Path of Current Through the UPS in Bypass Mode

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.

6−4 EATON Powerware® 9395 UPS (1000–1100 kVA) Installation and Operation Manual S 164201764 Rev 1 www.powerware.com