P.7 - Reactors for filtering - Circutor

Reactors for filtering
Switching micro-drop filtering
in the network and motor
Point PCC
Inverter
Other loads
The impedances of filters are generally
displayed on logarithmic charts, showing
the impedances related to a standard
value in order (in our case 0.1 Ω),
depending on the frequency (axis of
abcissas). The unit is displayed as (dB
/ 0.1 Ω) and defined as:
Z (dB / 0.1 Ω) = 20 · log [Z (filter) / 0.1 Ω]
Filter reactors for power converters
available. However, CIRCUTOR can
design and manufacture the adequate
reactors to cater for any need.
Fig. 2a and 2b show an example of the
typical response of two filter branches
for harmonics 5 and 7. Fig. 2c shows the
response of a bank of filters composed
of branches 5, 7, 11, 13 and an overlapping
stage for n > 15.
PCC voltage without
L red
Motor current without
L mot
PCC voltage with L red
Motor current with
L mot
The speed regulators for direct and alternating
current motors (frequency variators),
UPS systems and, in general, all
converters based on thyristors or power
transistors, are prone to the generation
of alterations in the network or an excessive
rippling in the direct current side
(motor, in the case of dc regulators).
These alterations affect adjoining equipment
and can even affect the operation
of the converter.
Mains current
without L cc
Mains current
with L cc
The basic types of problems are as follows:
Fig.2a. Response in branch frequencies
n = 5
Elimination of micro-drops
and filtering of harmonics
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Micro-drops in the voltage and excessive
di/dt on the network side with
the abovementioned equipment
Other loads
Commutation
choke
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Current peaks in frequency variators,
caused by the connection of capacitors
to the direct current stage
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Excessive rippling and switching
sparks in the motor of dc equipment
Absortion filter
Switching improvement
inductance in dc
All of these problems can be solved with
shock reactors or filters, as shown on
table 2.
Reactors for absorption filters
These filters are composed of the
branches, groups of L-C branches or
harmonics being filtered. The resonance
frequencies of the different groups are
identical to those of the harmonics being
filtered.
Fig.2b. Response in branch frequencies
n = 7
Mains current
without L cc
Table 1. Filter reactors
Mains current
with L cc
In construction terms, each branch is
similar to that of a rejection filter, but the
maximum harmonic current filtered is
the important information in this case, so
that the inductance and capacitor must
be dimensioned for such purposes.
There are many different requirements
and there are no standard components
Fig.2c. Response in filter frequencies with
n = 5, 7, 11, 13, >15
P7-4