FORM 160.77-O2
ISSUE DATE: 11/15/2011
SECTION 5 - DISPLAY MESSAGES
JOHNSON CONTROLS
125
5
Pri VSD Fault: High DC Bus Voltage XY
All DC bus voltages are continuously monitored and
compared to an over-voltage trip level of 2063VDC
(125% of 1650VDC). If any DC bus voltage exceeds
this level, the unit initiates a shutdown and the control
panel displays the message “PRI VSD FAULT: HIGH
DC BUS VOLTAGE XY”, where X denotes the Power
pole phase location (A, B or C) and Y denotes the loca-
tion of the cell within that phase (U, upper or L, lower).
Pri VSD Fault: Ground Fault
During startup and while running the drive will moni-
tor the peak value of the current being conducted (via
a DC current transformer) through a high impedance
earth referencing resistor tied between the neutral con-
nection of the three inverter power assemblies (which
are connected in a WYE) and the earth (ground) lug.
If the ground current continuously exceeds six milli-
amperes for 200 milliseconds, the control initiates a
safety shutdown and the system control panel displays
the message “PRI VSD FAULT: GROUND FAULT” .
Pri VSD Fault: Input Power Supply
The 120 VAC control supply that feeds the various DC
power supplies powering the MV VSD controls cir-
cuitry will be continuously monitored. If the 120 VAC
control supply drops to a nominal trip threshold of
84 VAC, the unit initiates a shutdown and the control
panel displays the message “PRI VSD FAULT: INPUT
POWER SUPPLY”.
In addition, the input voltage to the drive is monitored
using two potential transformers connected line-to-line
across the input of the unit’s power transformer. If the
cycle-by-cycle RMS value of the transformers input
voltage drops to a level of 70% of the nameplate volt-
age rating of the drive, the unit initiates a shutdown
and the control panel displays the message “PRI VSD
FAULT: INPUT POWER SUPPLY”.
Pri VSD Fault: Run Signal
Upon receipt of either of the two run commands (digi-
tal communications Run signal or hardwired 120 VAC
Run signal), a 5 second timer commences timing. If the
missing run signal is not asserted within the 5-second
window the MV VSD unit initiates a shutdown and the
control panel displays the message “PRI VSD FAULT:
RUN SIGNAL”.
Although this message can be generated by either run
signal being missing, it is almost always due to the loss
of the hardwired signal. This is because the loss of the
digital communications most likely will cause an ini-
tialization failure or serial communications message.
Pri VSD Fault: Interlock Fault
All doors that provide access to the areas that contain
medium voltage are either mechanically interlocked
via the input disconnect switch, or they contain micro-
switches to detect an open door. The micro-switches
act as door interlocks and drop out the input supply
vacuum switch if the doors are opened with medium
voltage applied to the unit.
In addition the drives display, which is mounted on
the inside of the low voltage compartment, contains a
display interlock switch that contains the capability to
prohibit the unit from be started by an external run sig-
nal. If the micro-switches for the doors are not closed
and control power is supplied or if the display interlock
switch is not closed, the drive initiates a safety shut-
down and the system control panel displays the mes-
sage “PRI VSD FAULT: INTERLOCK FAULT”.
Pri VSD Fault: Gate Driver XYZ
The unit contains three inverter power poles, one per
output phase. Each inverter power contains IGBT gate
driver control boards. These boards monitor the satu-
ration voltage appearing across IGBT’s #1 & #5 (two
upper most in the cell) and #4 & #8 (two lower most
in the cell) while gated on, and the isolated gate driver
power supply. If the IGBT’s saturation voltage exceeds
a prescribed limit, the gate driver will make the deter-
mination that a short circuit is present. This in turn will
cause the unit to initiate a cycling shutdown.
In addition, if the isolated power supply level falls be-
low a predetermined limit a cycling shutdown will be
initiated. The control panel will display the message
“PRI VSD FAULT: GATE DRIVER XYZ”, where X
is either A, B or C corresponding to the unit’s inverter
power cell connection to output terminals T1, T2 and
T3 respectively, Y denotes the location of the IGBT in
the pole in relation to its connection, either to the inter-
nal neutral connection of the poles or to the motor ter-
minal (N, neutral, indicates connection to the neutral,
M, motor, indicates connection to the motor terminal)
and Z denotes the location of the device relative to the
internal neutral connection (U, upper - #1 or #5 or L,
lower - #4 or #8).
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