7
05.01
7.2 Voltage matching
7-213
©
Siemens AG 2012 All Rights Reserved
SIMODRIVE 611 Configuration Manual (PJU) – 02/2012 Edition
Case 3:
If S
K plant
is less, then a transformer with a higher rating must
be selected, e.g. S
K plant
= 3000 kVA; otherwise as for Case 1:
S
n2
= 34 kVA
3000
820
3
(3000 – 820)
100
S
n2
> S
n1
% S
n2
is decisive
The matching transformer requires a rated power S
n
of 34 kVA
at a uk of 3%.
Case 4:
When compared to Case 3, the uk of the matching transformer
is reduced to, e.g. uk = 1%:
S
n2
= 11.3 kVA
3000
820
1
(3000 – 820)
100
S
n1
> S
n2
⇒
S
n1
is decisive
The matching transformer requires a rated power S
n
of 21 kVA
at a uk of 1%.
Note
S
n2
for the matching transformer can be reduced by reducing uk.
Condition a)
The rated power (Sn) of the matching transformer must always be:
S
n1
1.27
Pn (I/R module [kW])
[kVA]
Condition b)
In order to avoid faults and disturbances at the other loads, that are con-
nected to the secondary side of the matching transformer, the sum of the
system fault level (short–circuit power) of the plant connection and that of
the matching transformer at the connection point (S
K
line supply) must con-
tain at least the values shown in Table 7-1, Chapter C.1.3. Depending on the
vector group of the transformers, e.g. YYn0, asymmetric loading of the N/MP
may not be permitted.
Consequently, the required rated power S
n2
of the matching transformer is cal-
culated.
S
n2
[kVA]
S
K plant
S
K line
uk
(S
K plant
– S
K line
)
100
The system fault level at the plant connection S
K
plant plays a decisive role in
dimensioning/selecting the matching transformer.
From the rated power (Sn
1
or S
n2
) calculated under a) and b), the higher must
be used for the matching transformer.
S
n
calculation of
the matching
transformer for
several loads
Note:
7 Line Supply Connection
05.08
