Operating instructions

14 Operating Instructions
2.0 O
PERATING
I
NSTRUCTIONS
After the initial equipment start-up, the following operating guidelines can be used for standard
equipment operation. These guidelines should be reviewed for any special equipment modifica-
tions, special site conditions, or company policies that may require changes to the standard equip-
ment operation.
Description of Static Switch Operation—The Static Switch uses pairs of silicon controlled
rectifiers (SCRs) connected in paralleled opposing pairs to function as a switching contact. Three
pairs of SCRs connect the AC load to the selected “Preferred” source as long as the preferred
source is available. A second set of SCRs stands ready to transfer the AC load to the “Alternate”
source should the preferred source fail. The switching action is a very fast break-before-make
with less than a 1/4 cycle break in the AC waveform.
During static switch transfers and retransfers, the conduction state of the SCRs is carefully mon-
itored and controlled to prevent a current path from one source to the other. This technique pre-
vents a good source from feeding into the other faulted source.
The “Preferred” source is the source that will normally carry the load when both sources are avail-
able. The “Preferred” source is selectable by the user from the operator control panel. The unse-
lected source is referred to as the “Alternate” source and will carry the load if the “Preferred”
source should fail or if a manual transfer is initiated.
Maintenance Bypass—Manually operated, key-interlocked maintenance bypass provisions
allow bypassing of the Static Switch to either source and isolation of the Static Switch for mainte-
nance or repair. Refer to the Static Switch one-line diagram (Figure 7) and the maintenance
bypass operating instructions. While operating on maintenance bypass, all voltages can be
removed from the Static Switch electronics to facilitate safe repair.
All breakers of the Static Switch are plug-in types, which can allow any breaker to be replaced
without de-energizing the output bus. The Merlin Gerin breakers have an interlock in the plug-in
base, which prevents the breaker from being withdrawn in the ON position. The breaker will trip
OFF before it disconnects from the plug-in base.
2.1 Operator Control Panel
The Static Switch is furnished with a menu-driven operator control panel, which provides opera-
tor information and control of the Static Switch. A full-graphic liquid crystal display (LCD) is
used to display a mimic one-line diagram of the switch, monitored parameters, system status,
alarm information, history information, system setpoints, meter calibration, and operational pro-
cedures. Below the LCD are push-button switches for menu selection, alarm reset, and alarm
silence. The typical operator control panel is shown in Figure 10.
NOTE
Before unit is placed into service for the first time, after equipment
relocation, or after the equipment has been de-energized for an extended
period of time, a thorough equipment inspection and supervised start-up by
qualified personnel are strongly recommended. Contact your local Liebert
representative or Liebert Global Services at 1-800-543-2378 to arrange for
equipment inspection and start-up.