18 Digitax ST Installation Guide
www.controltechniques.com Issue: 2
4.3 EMC
4.3.1 Internal EMC filter
It is recommended that the internal EMC filter is kept in place unless there is a specific
reason for removing it.
Special attention is required when using a DST120X model on an ungrounded supply
(IT supply). In the event of a ground fault in the motor circuit the drive may not trip and
the filter could be overstressed. In this case, either the filter must be removed or
additional independent motor ground fault protection must be provided.
The internal EMC filter reduces radio-frequency emissions into the mains supply. Where
the motor cable is short, it permits the requirements of EN61800-3 to be met for the
second environment.
For longer motor cables, the filter continues to provide a useful reduction in emission
level, and when used with any length of shielded cable up to the limit for the drive, it is
unlikely that nearby industrial equipment will be disturbed. It is recommended that the
filter be used in all applications unless the ground leakage current is unacceptable or
the above conditions are true.
Figure 4-2 Removing the internal EMC filter and line to ground varistors
1. Internal EMC filter. Remove the bottom screw as shown.
2. Line to ground varistors. Remove the top screw as shown.
The supply must be disconnected before removing the internal EMC filter or line to
ground varistor screws.
WARNING
1
2
The line to ground varistors should only be removed in special circumstances.
NOTE
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