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Troubleshooting
Once the motor temperature reaches an acceptable level and the digital input from MCB 112 is deactivated, perform 1 of the
following:
Send a reset signal via bus or digital I/O.
Press [Reset].
7.2.68 ALARM 72, Dangerous Failure
Cause
Safe Torque Off (STO) with trip lock.
Troubleshooting
An unexpected combination of STO commands has occurred:
VLT
®
PTC Thermistor Card MCB 112 enables X44/10, but STO is not enabled.
MCB 112 is the only device using STO (specified through selection
[4] PTC 1 alarm
or
[5] PTC 12 warning
in
parameter 5-19 Termi-
nal 37 Safe Stop
). STO is activated, but X44/10 is not activated.
7.2.69 WARNING 73, Safe Stop Auto Restart
Cause
STO activated.
Troubleshooting
With automatic restart enabled, the motor can start when the fault is cleared.
7.2.70 ALARM 74, PTC Thermistor
Cause
The PTC is not working. Alarm is related to VLT
®
PTC Thermistor Card MCB 112.
7.2.71 ALARM 75, Illegal Profile Sel.
Cause
There was an attempt to write the parameter value while the motor was running.
Troubleshooting
Stop the motor before writing the MCO profile to
parameter 8-10 Control Word Profile
.
7.2.72 Warning 76, Power Unit Setup
Cause
The required number of power units does not match the detected number of active power units.
Troubleshooting
When replacing a drive module, this warning can occur if the power-specific data in the module power card does not match the
rest of the drive. Confirm that the spare part and its power card are the correct part number.
7.2.73 WARNING 77, Reduced Power Mode
Cause
The drive is operating in reduced power mode (less than allowed number of inverter sections). The warning is generated on power
cycle when the drive is set to run with fewer inverters and remains on.
7.2.74 ALARM 78, Tracking Error
Cause
The difference between setpoint value and actual value exceeds the value in
parameter 4-35 Tracking Error
.
Troubleshooting
Disable the function or select an alarm/warning in
parameter 4-34 Tracking Error Function
.
Investigate the mechanics around the load and motor. Check feedback connections from motor encoder to drive.
Select motor feedback function in
parameter 4-30 Motor Feedback Loss Function
.
Adjust the tracking error band in
parameter 4-35 Tracking Error
and
parameter 4-37 Tracking Error Ramping
.
AU275636650261en-000101 / 130R0334
712 | Danfoss A/S © 2022.12
Troubleshooting
VLT AutomationDrive FC 301/302
Programming Guide