Operation
3.3.3Momentary Overloads
An overload in the critical load will continue to be supplied by the UPS module if the overload condi- tion does not exceed the current versus time curve. The overload curve includes 150% of rated current for 30 seconds, 125% for 10 minutes and 104% continuously.
Momentary overloads from 155% to 1000% of rated current is supplied by pulsing the solid state static bypass switch for 40 milliseconds. This provides current from the bypass line in parallel with current from the UPS system output. By providing two power sources simultaneously, high current can be supplied to the critical load with full output voltage regulation. The critical load can be sus- tained through inrush currents and momentary faults without operating the motorized circuit break- ers. Pulse paralleling also serves, under some circumstances, as a backup in the event that an external bypass feeder breaker (e.g., BFB) trips open during this
If an overload condition exceeds 40 milliseconds, the UPS module continues to supply power to the critical load if it remains within the
Figure 44 Momentary overload (through pulse-parallel static switch)
THREE BREAKER MAINTENANCE BYPASS SWITCHBOARD
BFB | MBB |
| Critical |
| Load |
| AC Output |
BIB | MIB |
RIB
UPS MODULE
Static
Bypass
Switch
Static |
|
Switch | Bypass CB |
Disconnects |
CONTROL POWER
Controls |
MAIN INPUT
SWITCHGEAR
INPUT |
CB |
Rectifier/ |
Charger |
Inverter |
MBD |
OUTPUT |
CB |
Battery
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