Operational Modes
Ctrl Nr: PM375118-004
45
Retransfer = Yes:
•
If
Retransfer = Yes
, the load has an affinity for the Preferred Source. After transferring the load
to the alternate source, when the Preferred Source returns to a condition that is within tolerance
for at least the preset adjustable retransfer time delay, the load will be automatically be
retransferred back to the Preferred Source.
•
The load will always be transferred to the Preferred Source whenever the source is in-tolerance
—
—however long the Preferred Source takes to come back within specification—and will remain
connected to the Preferred Source until it fails or a transfer is manually initiated.
•
Retransfer = Yes
is the default setting for this control.
Retransfer = No:
•
The automatic retransfer to the Preferred Source can be disabled by an authorized user with
administrator, service, or PDI level privileges, by setting
Retransfer = No
.
•
If
Retransfer = No
, there is no affinity to the Preferred Source, except at startup. The logic will
transfer the load from the failing source to the “good” source and will remain on that source even
after the Preferred Source returns to acceptable limits. The only effect of specifying a Preferred
Source is to specify the source used at STS startup.
•
Retransfer = No
also allows the operator verify the power source prior to reapplying the critical
load. After verifying power reliability on the Preferred Source, the operator can force a manual
transfer back.
7.1.3
Manual Transfers
Manual transfers can be made in three ways:
1. In Normal Mode, from
Home
screen, switching the
Preferred Source
to the other source will
manually transfer the load to the other source if:
a. Preferred Source = Current Source, and
b. the new Preferred Source is within acceptable voltage limits and phase tolerances.
The selected transfer algorithm, VSS or POG, is used.
2. In Normal Mode, toggling the
SOURCE SELECTOR
momentary toggle switch on the
ROI panel
is an alternative way to set the
Preferred Source
. Transfer behavior is the same as in (1.) above.
3. In Redundant Mode, from the
ROI panel,
toggling the
SOURCE SELECTOR
momentary toggle
switch directly transfers the load to the other source, if not already on that source and the other
source is within specification. The SAS logic board controls the transfer, not the Monitor logic.
7.1.4
Special Transfer Situations
To keep power flowing to the output load, STS logic responds to several special circumstances:
•
Excessive transfers.
If transfers between sources become excessive, the logic dynamically
adjusts certain transfer parameters to minimize thrashing between sources until one or the other
power source stabilizes.
