Summation Transformers - Danfoss VLT AAF006 Operating Instructions Manual

Electrical Installation

4.2.9 Summation Transformers

Multiple current sources
Summation CTs are needed when the filter is to
compensate current from several sources. This is often the
case if a filter is installed in systems with generator back-
up or where the filter is only to compensate a limited
number of loads, for example, marine installations.
G
PCC1
M M
Illustration 4.11 Summation CTs on Generator Back-up
Applications (PCC-side)
MG90V302
Operating Instructions
PCC1
Illustration 4.12 Summation CTs Example for Individual
Harmonic Compensation (Load Side)
AAF
Summation current transformers are available with
M
multiple (2–5) inputs and a common output. For
applications where summations CTs are used to add
current from several sources, make sure that all CTs
connected to the summation are from the same
manufacturer and that the following aspects are the same:
NOTICE
Use summation CTs with great caution and always
ensure correct phase sequence, current direction,
primary and secondary rating. Incorrect installation
causes problems with filter operation.
The current transformers burden calculation includes all
wires in the installation and must be conducted for the
longest total wire string when using summation CTs.
Danfoss A/S © 09/2014 All rights reserved.
M M
•
Polarity.
•
Primary rating.
•
RMS value.
•
Accuracy (class 0.5).
•
Location (PCC or load-side).
•
Phase sequence.
4
AAF
M
23
4