APC Bypass Static User Manual download pdf (Page 6)

Page 6 10/05/09

and service of the UPS. The MBC shall completely isolate both the UPS input and output

connections. The MBC shall be used for paralleling of multiple UPS units.

2.3 INPUT POWER CONVERTER

A. General: The input power converters of the system shall constantly control the power imported

from the mains input of the system, to provide the necessary UPS power for precise regulation of

the DC bus voltage, battery charging, and main inverter regulated output power.

B. Input Current Total Harmonic Distortion: The input current THD shall be held to 5 percent or

less at full system load, while providing conditioned power to the critical load bus, and charging the

batteries under steady-state operating conditions. This shall be true while supporting loads of both

a linear or non-linear type. This shall be accomplished with no additional filters, magnetic devices,

or other components.

C. Soft-Start Operation: As a standard feature, the UPS shall contain soft-start functionality, capable

of limiting the input current from 0 percent to 100 percent of the nominal input over a default

15 second period, when returning to the AC utility source from battery operation. The change in

current over the change in time shall take place in a linear manner throughout the entire operation

(di/dt = constant).

D. Magnetization Inrush Current: The UPS shall exhibit 0 inrush current as a standard product. If

provided with an optional isolation transformer, inrush shall be limited to six times the nominal input

current of the transformer.

E. Input Current Limit: The system input current limit, shall be designed to provide 100 percent load

while fully charging the batteries at 10 percent of the system rating. The system shall be capable of

this with up to a +15 percent, -20 percent variation of the nominal input voltage.

F. Charging:

1. The battery charging shall keep the DC bus float voltage of ±220 volts, ±1 percent.

2. The battery charging circuit shall contain a temperature compensation circuit, which shall

regulate the battery charging to optimize battery life.

3. The battery charging circuit shall remain active when in static bypass and in normal operation.

4. The UPS shall be capable of limiting the energy sourced from the mains for purposes of battery

charging. As a default setting, the battery charge energy shall be set to 100 percent of its

nominal value. When signaled by a dry contact, (such as from an emergency generator) the

UPS shall be capable of limiting the battery charge energy taken from the mains. This shall

take place in Owner-selectable increments of 75 percent, 50 percent, 25 percent, 10 percent

and 0 percent of the nominal charge power. The selection shall be made from the UPS front

panel display/control unit.

G. Back-Feed Protection: The logic-controlled input contactor shall provide the back-feed protection

required by UL 1778.

2.4 OUTPUT INVERTER

A. General: The UPS output inverter shall constantly recreate the UPS output voltage waveform by

converting the DC bus voltage to AC voltage through a set of IGBT driven power converters. In

both normal operation and battery operation, the output inverters shall create an output voltage

independent of the mains input voltage. Input voltage anomalies such as brown-outs, spikes,

surges, sags, and outages, shall not affect the amplitude or sinusoidal nature of the recreated

output voltage sine wave of the output inverters.

B. Ov

erload Capability: Steady-state overload conditions, of up to 150 percent of system capacity,

shall be sustained by the inverter for 30 seconds in normal and battery operation. Overloads of

125 percent shall be sustainable by the inverter for up to 60 seconds. Should overloads persist past

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