4 Setting Up the MJ-4A & MJ-4B Control Panel
Siemens Energy, Inc. 31
90% · AutoVRCn% · (rated current).
Example 1
AutoVRC1%I = 60%; AutoVRCset1 = 3%.
I turn-off threshold = lower of:
60% · (1-2 · (3%)) · rated current = 56.4% · rated current
or
90%
· (60%) · rated current = 54% · rated current
Auto VRC will remain active until load current drops to
54% of rated current.
Example 2
AutoVRC1%I = 80%; AutoVRCset1 = 7%.
I turn-off threshold = lower of:
80% · (1-2 · (7%)) · rated current = 68.8% · rated current
or
90%
· (80%) · rated current = 72% · rated current
Auto VRC will remain active until load current drops to
68.8% of rated current.
To choose Automatic mode VRC, view VRC Mode and
select AUT/REM. Use AutoVRCset1 and AutoVRCset2 to
specify the reduction amount. Use AutoVRC1 %I and
AutoVRC 2%I to specify the low current threshold.
AutoVRC settings are overridden by contact closures on
terminal block contacts VRC1 and VRC2.
4.4.4 Voltage Limit Control
Voltage Limit Control (VLC) defines limits for load voltage.
When VLC is active, the microprocessor compares load
voltage with VLC setpoints. If load voltage changes to a
value above VLC Upper, or below VLC Lower, limiting
occurs immediately —that is, without waiting for the Time
Delay timer to count down. The appropriate LED indicator
(VLC Upper/VLC Lower) illuminates to alert the operator
that Voltage Limiting is in effect.
• To activate/deactivate VLC, view VLC Enable; then
use ON or OFF.
• To set the Upper VLC setpoint, view VLC Upper; then
enter a value between 106.0 and 134.0 volts.
• To set the Lower VLC setpoint, view VLC Lower; then
enter a value between 106.0 and 134.0 volts.
Note that the upper and lower limits must not overlap. For
example, if VLC Lower is 115, VLC Upper cannot be
changed to a value less than 115 V.)
4.5 Activating Data Logging—
the <LOG SETUP> Menu
The MJ-4
Control Panel can record status information that
will help reconstruct past occurrences. Two logs are main-
tained: an Event Log, and an Interval Log. Event Log
records are stored when predefined Events occur; Interval
Log records are stored at predefined time intervals. See
Table 4.6; default settings are in bold.
This section describes how to define your logging require-
ments. See Chapter 5, Reading and Interpreting MJ-4
Control Panel Data, for guidance on how to retrieve logged
data.
4.5.1 Event Logging
The Event Log captures present readings when an Event
occurs. You can determine which Events cause logging
activity by selecting the ones you want from the <LOG
SETUP> Menu. When that Event occurs, the following
readings will be logged:
Event Date and Time, Event Cause, Event ID
plus present values for:
Vld, Ild,
Table 4.6 The <LOG SETUP> Menu
DATA ITEM DESCRIPTION VALID INPUT
Log Event Enable event logging On or OFF
Event = Tap Define Tap Change
as event
On or OFF
Event = Neut. Define Tap at neutral
as event
On or OFF
Event = NN R Define Tap raise to
step NN as event
On or OFF NN=16
Event = NN L Define Tap lower to
step NN as event
On or OFF NN=16
Event = VLC Define VLC activa-
tion as event
On or OFF
Event = VRC Define VRC as event On or OFF
Event = PwrFlow Define power flow
reversal as event
On or OFF
Event = PwrCyc Define system
power up as event
On or OFF
Event = Cfg Define configuration
change as event
On or OFF
Event = Alert Define any Alert acti-
vation as event
On or OFF
Clr Event Log? Clear All Event Data Y or N
Clr IntervLog? Clear All Interval
Data
Y or N
Log Interval Enable Interval log-
ging
On or OFF
ResLogMinMax Reset min/max val-
ues at start of inter-
val
On or OFF
Log min/max Panel will log Instan-
taneous or Demand
Min/Max values
Inst, Dmd
Interval Logging Interval NNhrNNmin
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