Circutor AFQm Series, Instruction Manual

Page: 40 / 108

40
AFQm
Instruction Manual
To calculate this safety factor you must first know the parameter called short-circuit ratio R
SC
,
at the connection point of the PCL transducers (not on the installation input). The short-circuit
ratio is defined as the ratio between the short-circuit current of a mains ( I
SC
) and the rated cur-
rent of the set of non-linear transducers ( I
CNL
) producing the harmonics to be filtered.
(
Equation 6
)
𝑈𝑈
𝑛𝑛
% =
𝑈𝑈
𝑛𝑛
𝑈𝑈
1
∗ 100
𝐼𝐼
𝑛𝑛
% =
𝐼𝐼
𝑛𝑛
𝐼𝐼
1
∗ 100
𝑈𝑈 = �𝑈𝑈
1
2
+ 𝑈𝑈
2
2
+ 𝑈𝑈
3
2
+ 𝑈𝑈
5
2
+ ⋯
𝐼𝐼 = �𝐼𝐼
1
2
+ 𝐼𝐼
2
2
+ 𝐼𝐼
3
2
+ 𝐼𝐼
5
2
+ ⋯
𝑇𝑇𝑇𝑇𝑇𝑇 ( 𝑈𝑈 )% =
�𝑈𝑈
2
2
+ 𝑈𝑈
3
2
+ 𝑈𝑈
5
2
+ ⋯
𝑈𝑈
1
𝑇𝑇𝑇𝑇𝑇𝑇
(
𝐼𝐼
)% =
�𝐼𝐼
2
2
+ 𝐼𝐼
3
2
+ 𝐼𝐼
5
2
+ ⋯
𝐼𝐼
1
𝐼𝐼
𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹
= 𝐼𝐼
𝐹𝐹𝑅𝑅𝑅𝑅
− 𝐼𝐼
𝐶𝐶𝐶𝐶𝐹𝐹𝐶𝐶𝐶𝐶
𝐼𝐼
𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹
(
𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴
) = [
𝐴𝐴𝐹𝐹
ℎ
∗ 𝐼𝐼
𝐶𝐶𝐶𝐶𝐹𝐹𝐶𝐶𝐶𝐶
∗ 𝑇𝑇𝑇𝑇𝑇𝑇 ( 𝐼𝐼 )]
𝑅𝑅
𝑆𝑆𝐶𝐶
=
𝐼𝐼
𝑆𝑆𝐶𝐶
𝐼𝐼
𝐶𝐶𝐶𝐶𝐹𝐹
Equation 6:Calculating the short-circuit ratio R
SC
�
In a real installation, the short-circuit current ( I
SC
) in the PCL can be assessed by having the
voltage at the said point for two different load currents.
For example, full load, I
A
and 10% load, I
B
. If V
OC
is the rated voltage at no-load, the I
SC
, can be
calculated using the formula shown in
Figure 33
:
Figure 33:Graph for calculating I
SC
�
The safety factor ( FS
h
) can be obtained from the graph in
Figure 34
:
Figure 34:Approximate graph for calculating the FS
h
�