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MBS arrangement. (There are some indirect possibilities. For example, stopping the UPS
by pressing the EPO could cause the On Bypass signal from the UPS to the Transformer
Cabinet with MBS arrangement to change, tripping the Bypass Breaker if the UPS Output
Breaker is also closed. These indirect actions will not affect system operation if the system
is operated according to the procedures in
Section 5. Operation (MBS Arrangement
Only)
.)
Some users prefer to use a normally open switch in the REPO system; others prefer a
normally closed switch. Inputs for both types of switches are provided in the Transformer
Cabinet with MBS arrangement, but the normally closed function has to be enabled by
operating a small rocker switch on the Options Control Board. This is to avoid the problem
of not being able to operate the system if the normally closed circuit is missing, as when the
user only chooses to use the normally open configuration, or when the user does not
choose to use the REPO system at all.
Historically, REPO systems have caused a lot of confusion due to systems not being
capable of operation due to a false signal from the REPO switch(es). To address this issue,
the Options Control Board has a yellow LED lamp (DS1 in the upper right corner of
Figure
6)
that indicates that the REPO has been activated. The logic that operates the lamp
latches the indication, so it is possible to determine that the REPO was activated at some
time since power was applied to the system. The latched indication can be reset by
pressing S1 on the Options Control Board.
Some users prefer that power not be restored to the load automatically, if lost, so that they
can manually reapply power to the connected loads using a defined sequence. There is a
rocker switch on the Options Control Board that selects this capability. If the switch is ON
and power is lost (both the utility input power to the cabinet and the power from the UPS),
Breakers #2 and #3 will both trip, assuring that the load cannot be powered without
manually closing one of these breakers. Sometimes this feature is called "Manual Restart".
