7
05.01
7.2 Voltage matching
7-212
©
Siemens AG 2012 All Rights Reserved
SIMODRIVE 611 Configuration Manual (PJU) – 02/2012 Edition
Condition a)
The rated power (Sn) of the matching transformer must be:
S
n1
1.27
Pn (I/R module [kW])
[kVA]
Example: The minimum rated power of a matching transformer
for I/R module 16/21 is 21 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
This means:
Sn1, Sn2
Calculated rated power of the matching transformer
uk
Short–circuit voltage of the matching transformer as % (see Table 7-2)
S
K
Short–circuit power.
S
K plant
if necessary, consult the utility company
S
K line
= at least the value contained in Chapter C.1.3,Table 7-1
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.
Matching transformer for 16/21 kW I/R module sinusoidal current:
uk matching transformer = 3%; S
K plant
= 50000 kVA ; S
K line
for I/R 16/21 kW
sinusoidal current according to Table 7-1: S
K line
= 1120
0.73
=
820 kVA
based on a)
S
n1
= 1.27
16 kW = 21 kVA
based on b)
Calculation of Sn2
Case 1:
S
n2
= 25 kVA
50000
820
3
(50000 – 820)
100
S
n2
> S
n1
⇒
S
n2
is decisive
The matching transformer requires a rated power S
n
of 25 kVA
at a uk of 3%.
Case 2:
If the uk of the matching transformer is less than, e.g. uk=1%
for otherwise unchanged conditions for Case 1:
S
n2
= 8.3 kVA
50000
820
1
(50000 – 820)
100
S
n1
> S
n2
⇒
S
n1
is decisive
The matching transformer requires an Sn rated power of 21 kVA
at a uk of 1%.
S
n
calculation of
the matching
transformer for an
NE module
Note:
Examples
7 Line Supply Connection
05.08
