PCC1
AAF
M
M
M
130BB514.11
Illustration 4.33 Current transformers installed on load side for
group compensation.
If the current transformers are installed on the source
(PCC) side the filter will expect a sinusoidal (corrected)
signal feedback form the three sensors. In case the sensors
are installed on the load side the received signal will be
subtracted from the ideal sine wave to calculate the
needed corrected current.
NOTE
Erratic filter operation can be a result of incorrect current
transformers connection point programming
4.5.8 Auto CT Detection
The VLT Active Filter is able to perform an auto detection
of the installed CT. The CT auto detection can be
conducted both while the system is running and at no
load conditions. The filter injects a prefixed current of
known amplitude and phase angle and is measuring the
returned CT input. The performance is conducted on each
phase individually and for several frequencies to reassure
phase sequence and RMS is set correctly.
The Auto CT detection is pending on the follow conditions:
-
Active Filter bigger than 10% of CT RMS rate
-
CTs installed on source (PCC) side (auto CT not
possible for load side CT installation)
-
Only one CT per phase (not possible for
summation CTs)
-
CTs are part of below standard range:
600
750
1000
1250
1500
2000
2500
3000
3500
4000
Table 4.6 Primary Rating [A]
Most restrictions on the current transformers comes from
the installation, such as needed cable length, temperature
conditions, square section of conducts, standard or split
core layout, etc. A broad range of different current
transformers can be used independently of brand and
type.
For specific CT requirements contact the local supplier or
go to
http://www.deif.com/Download_Centre/Search.aspx?search-
string=dct:
Secondary Primary
Accuracy Burden
Type
Description
5 or 1A
30 -
7500A
0.2 - 0.5-1 1.0 - 45V
A
ASR
ASK
EASR
EASK
Measuring
current
transformer
for cables
and bus bars
5 or 1A
100 -
5000A
0.5 - 1
1.25 -
30V A
KBU
Split core
current
transformer
5 or 1A
5 or 1A
0.5 - 1
15 - 30V
A
KSU/
SUSK
Summation
current
transformer
Table 4.7 Standard CT Range from Deif - Fits Most Applications
4.5.9 Summation Transformers
Multiple current sources:
In case the filter is to compensate current from several
sources it is needed to install summation CTs. This is often
the case if filter is installed in systems with generator back-
up or where the filter is only to compensate a limited
number of loads.
How to Install
VLT Active Filter AAF 00x
MG.90.V2.02 - VLT® is a registered Danfoss trademark
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