Page 58 - ELECTRONICON_Key-Components-50Hz

DEFINITIONS AND SELECTION CRITERIA

I. Non-adapted Rating:
The non-adapted reactor is matched to a power capacitor with standard rating at system voltage. This allows for use of capaci-
tors “off the shelf”. However, with the increased output of kvar due to voltage rise inside the LC circuit, more power output is
installed than actually required: the kvar output of a capacitor depends on the voltage it is charged with, and at higher voltage,
equal capacitance delivers more kvar (in the example below: 26.9 instead of 25 kvar). In this case, the rated power of the capa-
citor is used to define the reactor rating.
»!« Caution: Bear in mind that the capacitors to be detuned will be exposed to increased voltage; excessive voltage

load may lead to reduced life or even failure or destruction of the capacitor!
»!« Check capacitance and general state of the capacitors before adding detuning reactors to existing non-detuned
sys tems as these may have been harmed by their previous operation without reactor protection!

DEFINITIONS AND SELECTION CRITERIA
Capacitor 275.186-516600 (page 27) with 25kvar 400V 50Hz 3 × 166μF (498μF) shall be detuned to 189Hz (p = 7%).
Example
Calculation Step 1: Determination of the reactor

Capacitor Reactance Required reactance of the reactor Required inductance
1 X

X = X · p = 6.39 Ω · 0.07 = 0.45 Ω
L =
X = = 6.39 Ω C 2 πf L = 1.432 mH
L
C
2 πf · C
Step 2: Calculation of resulting PFC current and net kvar output into the mains
PFC current
X = X -X = 5.94 Ω Real PFC output into mains

C
L
total
U 400 V Q = U mains · I = 400 V · 67.3 A
LC
C
I = mains = 67.3 A* = 26.9 kvar
=
C
X total 5.94 Ω
Selection Step 1: Determination of the reactor
from catalogue Alternatively, reactors matching the most common capacitor ratings can be selected directly from our data charts
of reactors with “non-adapted rating” (page 48):
Look up the mains voltage 400 V Select the capacitance of your Find 444.125-40D2A
in combination with 7 % intended capacitor (3 × 166 μF) “FK-Dr 25/400/50/7/D“

Step 2: Determination of net kvar output into the mains and calculation of PFC current

Calculate PFC current:
Look up the kvar value under Q (U ):
N
LC
26.9 kvar I = Q lc 26.900 var = 67.3 A*
=
U
C
N
400 V
(*current over three phases = phase current · 3 )
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