JOHNSON CONTROLS
238
FORM 201.23-NM2
ISSUE DATE: 3/9/2015
SECTION 8 - MICROPANEL
High Motor Current (Hardware) Fault
The three output lines to each phase of the compres-
sor motor are monitored via three current transformers
within the VSD. The unit’s three phases of instanta-
neous output current will be compared to a predeter-
mined limit, which is contained in hardware. The nom-
inal peak current trip level is 575.5 Amps (554A min.,
597A max.). 380VAC, 60Hz and 400VAC, 50Hz nomi-
nal peak current trip level is 649.5 Amps (626 Amps
min., 674 Amps max.). The variation in trip point is
the result of component tolerances on the VSD Logic
Board. If the peak current limit is exceeded, the unit
will fault and shutdown immediately.
This fault is an auto-restart safety that will lock out
system on the 3rd fault in 90 minutes. The fault will
be an individual system/compressor fault for all units.
Following is a sample Status display fault message:
SYS X YYYYYYYY HIGH MOTOR CURRENT
X indicates the system and YYYYYYY indicates the
system is in a “FAULT” condition and will restart or
“LOCKOUT” and will not restart until the operator
clears the fault using the keypad.
Motor Current Overload (Software) Fault
The Motor Current Overload will compare the highest
of the 3 phases of motor current per compressor to the
compressor’s 105 % FLA ADJUST (overload) potenti-
ometer setting on the VSD Logic Board. If the current
exceeds the setting continuously for 20 seconds, the
compressor will trip.
This safety will lock out a system on the 1st fault and
shut down with a controlled ramped shutdown. The
fault will be an individual system/compressor fault for
all systems. A sample Status display fault is shown be-
low:
SYS X YYYYYYYY MOTOR CURRENT OVERLOAD
X indicates the system and YYYYYYY indicates the
system is in a “LOCKOUT” condition and will not re-
start until the operator clears the fault using the keypad.
Motor Current Overload (Hardware) Fault
The Motor Current Overload will compare the highest
of the 3 phases of motor current per compressor to the
compressor’s overload ADJUST potentiometer setting.
If the current exceeds the setting continuously for 30
seconds, all compressors will fault and shut down im-
mediately.
The fault will be a unit fault and will lock out all sys-
tems on the first fault. A sample Status display fault is
shown below:
UNIT YYYYYYYY
MOTOR CURRENT OVERLOAD
YYYYYYYY indicates the unit is in a "Lockout" con-
dition and will not restart until the operator clears the
fault using the keypad.
IGBT Gate Driver (Hardware) Fault
The unit’s phase bank assembly(s) contains one IGBT
gate driver control board per compressor. These boards
monitor the saturation voltage drop across each of the
six IGBT’s while gated on. If the IGBT’s saturation
voltage exceeds the prescribed limit, the gate driver
will make the determination that a short circuit is pres-
ent. This in turn will cause the system to trip. During
normal operation, the voltage drop across a saturated
IGBT is low. When a short or shoot occurs, the ex-
tremely high current causes the voltage across the de-
vice to increase. When the electronic hardware on the
IGBT Gate Driver Board senses the current rise, it im-
mediately turns off all IGBT’s in the module and the
system will shut down immediately.
Additionally, if the IGBT’s Gate Driver board’s power
supply voltage falls below the permissible limit, this
same fault will be generated.
This is an auto-restart safety that will lock out on the
3rd fault in 90 minutes. The fault will be a system fault
for all units. Following is the Status display fault mes-
sages for all systems.
SYS X YYYYYYYY GATE DRIVER
X indicates the system and YYYYYYY indicates the
system is in a “FAULT” condition and will restart or
“LOCKOUT” and will not restart until the operator
clears the fault using the keypad.
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