Liebert 610 manual Momentary Overloads, Momentary overload through pulse-parallel static switch

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 pulse-paralleling period, retaining the UPS inverter connection with the critical load.

If an overload condition exceeds 40 milliseconds, the UPS module continues to supply power to the critical load if it remains within the current-versus-time curve of overload capacity. If the system overload capacity is exceeded, the UPS control logic completes an automatic transfer to the bypass line by operating the motorized system circuit breakers (output and bypass). Refer to 3.5 - Auto- matic Operations.

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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