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AFQm IP54
To avoid this phenomenon, it is best to oversize the active filter by multiplying the initial current of
harmonics measured in the load by a safety factor (FS
Where:
I
(AFQm): rated current of the active filter.
FILTER
FS
: safety factor > 1.2.
h
I
: maximum current of the load.
LOAD
THD(I): harmonic distortion of the load current.
To calculate this safety factor you must first know the parameter called short-circuit ratio R
connection point of the PCL transducers (not on the installation input). The short-circuit ratio is de-
fined as the ratio between the short-circuit current of a mains (I
non-linear transducers (I
In a real installation, the short-circuit current (I
the said point for two different load currents.
For example, full load, I
A
using the formula shown in
The safety factor (FS
) can be obtained from the graph in
h
Instruction Manual
���� = �����
+ ����
2
1
������������ ( ���� ) % =
I
(AFQm) = [FS
FILTER
������������ ( ���� ) % =
����
= ����
�������� ���� ������������
Equation 6: Rated current of the AFQm.
����
( ���������������� ) = [ ��������
�������� ���� ������������
) producing the harmonics to be filtered. (
CNL
����
Equation 7: Calculating the short-circuit ratio R
SC
and 10% load, I
. If V
is the rated voltage at no-load, the I
B
OC
:
Figure 23
Figure 23: Graph for calculating I
+ ����
+ ����
+ ⋯
2
2
2
2
3
5
�����
+ ����
+ ����
+ ⋯
2
2
2
2
3
5
����
). In other words:
1
h
* I
* THD(I)]
h
LOaD
�����
+ ����
+ ����
+ ⋯
2
2
2
2
3
5
����
1
− ����
������������
��������������������
∗ ����
∗ ������������(����) ]
ℎ
��������������������
) and the rated current of the set of
SC
Equation 7
����
=
��������
����
��������
������������
.
SC
) in the PCL can be assessed by having the voltage at
.
SC
:
Figure 24
, at the
SC
)
, can be calculated
SC
117
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