Functions
68
7UM62 Manual
C53000-G1176-C149-3
Conversion to
Secondary Values
The factor K can be derived from the unbalanced load characteristic according to
Figure 2-23 by reading the time corresponding to the
at the point I
2
/I
N
= 1.
Example:
t
perm
= 20 s for I
2
/I
N
= 1
The constant K
primary
= 20 s determined in this way is valid for the machine side
(primary side).
The factor K
primary
can be converted to the secondary side by means of the following
formula:
The calculated asymmetry factor K
sec
is set as
at address
Setting value at address
Figure 2-23
Example of an Unbalanced Load Characteristic Specified by the Machine
Manufacturer
Example:
I
N Machine
= 483 A
I
N CT prim
= 500 A
Factor K
primary
= 20 s
K
sec
K
primary
I
N Machine
I
N CT prim
------------------------
è
ø
æ
ö
2
⋅
=
20 s
483 A
500 A
---------------
è
ø
æ
ö
2
⋅
18,7 s
=
FACTOR K
=
10
100
1000
50
500
0.06
1.0
0.5
0.4
0.3
0.1
0.2
0.11
t/s
I
2
/
I
N
max. perm. I
2
/I
N
in permanent operation
max. perm. I
2
/I
N
in case of a system fault
20
30
40
