Installation and User Manual
3.9Open SCR Protection
The STS design includes sensing circuits to detect an open SCR and in addition to the following actions, will initiate audible and visual alarms:
In the event of an open SCR in the active source powering the load, the unit will alarm and immediately transfer to the inactive source. Then the SCR isolation switch on the previously active source will be shunt tripped. Automatic retransfer will be inhibited under such conditions until repair is made and the system is reset.
3.10Source Cross-Connection Protection
The STS transfer logic will check that the two input sources, of any combinations, are never connected in a fashion to allow current flow from one source to the other without first passing through the load. The logic circuitry has protective sensing circuits that prohibit this conduction. Transfers and retransfers between sources will be break-
3.11Bypass Procedure
Bypass Load to Source #1
1.The Source #1 SCR Switch #1 must be indicated closed on the display panel. If not, transfer the load to Source #1 by turning the Manual Control key switch on the front display panel to the “ON” position and pressing the Change Preferred Source Pushbutton. The STS should transfer to Source #1.
2.Open Source #2 isolation switch, CB2. (For
3.Lock Source #2 bypass switch, CB5, and remove the key.
4.Using the key(s), unlock and close Source #1 bypass switch, CB4. CB1, CB3A and CB3B (if installed) will shunt trip, isolating the static switch section.
Return to Normal Operation (load on Source #1)
1.Close Source #1 isolation switch, CB1.
2.Wait for indication on the display panel that Source #1 SCR Switch #1 is closed.
3.Close Output isolation switch(es), CB3A and CB3B (if installed).
4.Open Source #1 bypass switch, CB4, and lock.
5.Close Source #2 isolation switch, CB2. (For
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