Safety Functions; Maintenance Functions - Danfoss VLT AQUA FC 202 Design Manual

VLT® AQUA Drive FC 202
Design Guide

5.2.2 Safety Functions

5.2.2.1 Safe Torque Off (STO)
STO is the required base for drive-based functional safety as defined per EN IEC 61800-5-2, as the STO function brings the drive
safely to a no-torque state. STO is typically used for preventing an unexpected start-up (EN 1037) of machinery, or for an emergency
stop fulfilling stop category 0 (EN 60204-1).
When STO is activated, it immediately switches off the drive output to the motor. Motor speed then coasts to a stop.
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Illustration 21: Motor Speed Coasts to Stop After Activation of STO

5.3 Maintenance Functions

Danfoss VLT® drives feature preventive and condition-based monitoring functions.
5.3.1 Preventive Maintenance
Schedule maintenance based on a running hours counter. When planned maintenance occurs, the drive shows a message. Action
flags can be transferred via fieldbus. Parameter group 18-0* Maintenance Log contains the last 10 preventive maintenance events.
Maintenance log 0 is the latest log and maintenance log 9 is the oldest.
Parameters 18-00 to 18-03 show the maintenance item, the action, and the time of the occurrence.
The alarm log key gives access to both alarm log and maintenance log.
5.3.2 Condition-based Monitoring
The function uses the drive as a smart sensor for monitoring the condition of the motor and application. The VLT AQUA Drive fea-
tures licensed functions that enforce predictive maintenance actions, such as:
• Motor stator winding monitoring.
• Vibration monitoring.
• Load envelope monitoring.
Set various thresholds and determine the baseline with different methods according to relevant standards and guidelines such as
the ISO 13373 standard for Condition Monitoring and Diagnostics of Machines or the VDMA 24582 guideline for condition monitor-
ing.
The condition-based maintenance parameters are in parameter group 45-** Condition Based Monitoring.
5.3.2.1 Motor Stator Winding Monitoring
Motor winding failures lead to stop of operation and, thus, unwanted downtime. Motor winding failures start with a short circuit
between 2 windings. Over time, the short circuit leads to a motor short circuit fault. By using the motor stator winding monitoring
function, motor isolation faults are detected at an early stage, allowing maintenance of the motor before the winding fails entirely
due to overheating.
• By analyzing the motor current signature, the drive detects motor winding damage at an early stage.
• The function does not require any external sensors.
• The drive sends a warning/alarm to the LCP or fieldbus.
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