Summation current transformers are available with
multiple (2-5) inputs and 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
CT have the following:
-
The same polarity
-
The same primary rate
-
The same RMS value
-
The same accuracy (class 0.5)
-
The same location (PCC or load-side)
-
The same phase sequence
NOTE!
Use summation CT with great caution and always ensure
correct phase sequence, current direction, primary and
secondary rate. If installation is incorrect the filter will not
work according to expectations.
The current transformer's burden calculation has to include
all wires in the installation and must be conducted for the
longest total wire string when using summation CTs.
4.5.10 Active Filter Operating with
Capacitor Banks
The VLT Active Filter is able to run in conjunction with
capacitor banks as long as the resonance frequency of the
capacitor bank is not in the operation range of the active
filter.
NOTE!
Always use detuned capacitor banks in installation with
Adjustable frequency drive and active filters to avoid
resonance phenomena, unintended tripping or even
component break down.
For the case of detuned capacitors, the resonance
frequency capacitors should be tuned for an inter-
harmonic number lower than the third harmonic. The VLT
Active Filter has to operate in selective compensation
mode if the filter is installed in conjunction with capacitor
banks of any kind.
Capacitor bank should ideally be installed upstream from
the filter/towards the transformer. If that is not possible,
the current transformers should be installed in a way that
they do not measure both needed current compensation
and the capacitor corrected current.
PCC1
M
M
AAF
130BB517.11
Figure 4.36 Capacitor bank mounted up-stream and CT's instal-
lation does not measure capacitor current.
shows recommended installation of the active
filter and CT placement in installations holding capacitor
banks.
How to Install
VLT Active Filter AAF 00x
MG.90.V2.22 - VLT
®
is a registered Danfoss trademark
4-27
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