ABB DCS 400 - Connection of Single and Three Phase Filters; Three-Phase Filters

II K 5-7
Installation
2
Three-phase filters
EMC filters are necessary to fulfil EN 50081 if a converter shall be
run at a public low voltage line, in Europe for example with 400 V
between the phases. Such lines have an earthed neutral conduc-
tor. ABB offers suitable three - phase filters for 400 V and 25
A...600 A and 500 V filters for 440 V lines outside Europe (see Ap-
pendix A).
Lines with 500 V to 1000 V are not public. They are local lines in-
side factories, and they do not supply sensitive electronics. There-
fore converters do not need EMC filters if the
y
shall run with 500 V
and more (see also
6).
3 Single-phase fil-
ters for field
supply
Many field supply units are single - phase converters for up to 50 A
excitation current. The
y
can be supplied b
y
two of the three input
phases of the armature supply converter. Then a field supply unit
does not need an own filter as shown at the connection example
(
24).
If the phase voltage to the neutral conductor shall be taken (230 V
in a 400 V line) then a separate filter is necessar
y
as shown below.
ABB offers such filters for 250 V and 6...55 A (see Appendix A).
3-PH FILTER
1-PH FILTER
0
L1
L2
L3
N
Figure 5.2 - 2 Connection of single and three phase filters
4 Line chokes
(Commutation
chokes)
Converters cause short-duration short circuits at their AC inputs, so
- called commutation notches. Such notches down to 0 V (100%
depth) can be accepted at the secondary windings of converter
(dedicated) transformers (operation without line chokes). However,
their depth must be reduced if the same transformer shall supply
more than two converters of comparable power. In such case line
chokes are necessary. They must cause about 1% relative voltage
drop at rated current. So - called 1% chokes are also necessar
y
if
the power of the converter is very low compared with the available
power of the transformer or supply line. ABB offers suitable 1%
chokes.
According to the European product standard EN 61800-3, the
commutation notches must be kept below 20% of the line volta
g
e
in the first environment, whereas an upper limit of 40 % is specified
for the second environment. This tar
g
et can be achieved with the
aid of line chokes. The inductance of these chokes to be applied in
the first environment must have 4 times the value of the network
inductance at the converter’s connection point (point of common
couplin
g
, PCC) as shown in Fi
g
ure 5.2-3. Therefore in man
y
cases
so-called 4% chokes are necessary, and therefore ABB offers also
suitable 4% line chokes besides the 1% chokes.