Siemens SINAMICS S120 - Page 142

Line connection and line-side power components
3.11 Line connection variants
Booksize Power Units
142 Manual, (GH2), 07/2016, 6SL3097-4AC00-0BP8
An isolating transformer / autotransformer (matching transformer) must be dimensioned for
the total of all loads connected to it. The apparent power required for the Line Modules must
be determined and added as indicated in table "Transformer configuration instructions". If the
transformer is underdimensioned (S
n
or S
k
), this can lead to increased line voltage dips and
faults in the line supply and in other loads at this connecting point.
If other loads are connected to the secondary side of the matching transformer, the boundary
conditions indicated under a) and b) must be complied with when selecting the matching
transformer.
S
n1
, S
n2
= calculated rated power of the transformer resulting from a) and b)
u
k
= short-circuit voltage of the matching transformer in %
(must be between 1% and 3% for Active Line Modules and Smart Line Modules)
S
K
= short-circuit power.
Supplementary condition
Limitation a)
The rated power of the matching transformer S
n1
must as a minimum always be a factor of
1.27 higher than the rated power P
n
of the Line Module.
S
n1
≥ 1.27 • P
n
Example:
The minimum rated power of a matching transformer for a 16 kW Line Modules is 21 kVA.
Limitations b)
In order to avoid faults and disturbances at the other loads that are connected to the
secondary side of the matching transformer, the short-circuit power of the plant connection
(S
K factory
) and that of the matching transformer at the connection point (S
K line
) must reach at
least the following values.
S
K line
≥ 70 • P
n
(for Active Line Module and Smart Line Module)
S
K line
≥ 30 • P
n
(for Basic Line Module)
Special case:
When operating with only one supply at a transformer, the values may be reduced to a factor
0.73.
S
K line
≥ 0.73 • 70 • P
n
(for Active Line Module and Smart Line Module)
S
K line
≥ 0.73 • 30 • P
n
(for Basic Line Module)
For example S
K line
for 16 kW Active Line Module: S
K line
= 0.82 MVA = 820 kVA