REG 316*4 1MRB520049-Uen / Rev. F ABB Switzerland Ltd
3-127
Alternative 2 with grounding transformer (see Fig. 3.5.11.5):
This arrangement is widespread in North America. The maxi-
mum current for the grounding transformer is chosen to ap-
proximately equal the capacitive component of the E/F current.
I
Emax
» I
C
IC
U
C
GN
=´ ´ ´3
3
w
Rated data of the grounding transformer:
U
U
n
GN
1
3
=
U
2n
= 100; 200; 400 V or 115; 230; 460 V
I
1n
= I
Emax
I
2n
= I
e
where
II
U
U
eE
n
n
=
max
1
2
The grounding resistor R
e
connected to the secondary is give by
R
U
I
U
U
e
GN
E
n
n
=
æ
è
ç
ö
ø
÷
3
2
1
2
max
or for U
U
n
GN
1
3
=
R
U
UI
e
n
nE
=
2
2
1 max
Rated power of the grounding transformer:
S
n
= U
1n
I
1n
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