Uninterrupted Transfer

2.5.1

The static bypass transfer switch shall automatically cause the bypass ac

power source to assume the critical load without interruption when the

bypass control logic senses one of the following conditions and the UPS

inverter output is synchronized to the bypass ac power source:

a.

Inverter overload exceeds unit's rating.

b.

Battery protection period is expired and bypass is available.

c.

Inverter failure.

2.5.2

Interrupted Transfer

If an overload occurs and the UPS inverter output is not synchronized to

the bypass ac power source, the UPS inverter output shall current-limit for

200 milliseconds minimum. The inverter shall then turn off and an

interrupted transfer to the bypass ac power source shall be made. If the

bypass ac power source is beyond the conditions stated below, an

interrupted transfer shall be made upon detection of a fault condition:

a.

Bypass voltage greater than plus or minus 10 percent from the UPS

rated output voltage.

b.

Bypass frequency greater than plus or minus 0.5 Hz from the UPS

rated output frequency.

c.

Phase differential of ac bypass voltage to UPS output voltage

greater than plus or minus 3 degrees.

2.5.3

Manual Transfer

It shall be possible to make a manually-initiated static transfer from the

system status and control panel by turning the UPS inverter off.

2.5.4

Automatic Uninterrupted Forward Transfer

The static bypass transfer switch shall automatically forward transfer,

without interruption after the UPS inverter is turned "on", or after an

instantaneous overload-induced reverse transfer has occurred and the load

current has returned to less than the unit's 100 percent rating.

2.5.5

Forced Transfer

The control logic circuitry shall provide the means of making a forced or

reverse transfer of the static bypass transfer switch on an interrupted

basis. Minimum interruption shall be 200 milliseconds when the UPS

inverter is not synchronized to the bypass ac power source.

2.5.6

Overload Ratings

The static bypass transfer switch shall withstand the following overload

conditions:

a.

2000 percent of UPS output rating for two cycles.

b.

200 percent of UPS output rating for 5 minutes.

SECTION 16265A

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