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6.4.2. CT' s connection topology: cases
The location of the CT' s is critical to ensure the proper operation of the active
filter. The CT' s are the " eyes" of the filter and it will react in accordance with
the information supplied by them.
The location of the CT' s must always be in closed loop configuration. This
means that the CT' s must see the load current and the filter current.
In some cases, summation CT' s might be needed to fulfil the closed loop
requirement.
Typical circuit topologies and adequate CT' s location are described hereafter
in the following order:
Case 1: Global compensation – one feeding transformer.
Case 2: Individual compensation – one feeding transformer.
Case 3: Global compensation – transformer busbar not accessible.
Case 4: Two independent feeding transformers.
Case 5: Back up generator.
Please bear in mind that the active filter always needs 3 CT' s: one per phase.
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This is the most frequent configuration: one transformer feeds several non-
linear loads. The active filter is installed in central position and filters the
combined harmonic currents.
This configuration and the proper location of the CT' s is represented
hereafter.
Figure 6.1. Global compensation – one feeding transformer.
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PQF
Asea Brown Boveri Jumet S.A.
PQFA Instructions Manual
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LOAD LOAD LOAD
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