Siemens SINAMICS S120 - Page 144

Line connection and line-side power components
3.11 Line connection variants
Booksize Power Units
144 Manual, (GH2), 07/2016, 6SL3097-4AC00-0BP8
Table 3- 34 Engineering information for transformers for Basic Line Modules
Rated power P
n
Required rated power of the
isolating transformer / auto-
transformer
S
n
(1.27 • P
n
)
Required short-circuit volt-
age U
k
Minimum system fault level
required
S
K line
(30 • P
n
)
20 kW
≥ 26 kVA
≤ 10%
≥ 0.6 MVA
40 kW ≥ 51 kVA ≤ 10% ≥ 1.2 MVA
100 kW
≥ 127 kVA
≤ 10%
≥ 3.0 MVA
Note
Ask your local power utility company for the short
-circuit power at the plant connection S
K
factory
.
Example 1
u
k
matching transformer = 3 %
S
K factory
= 50000 kVA
S
K line
= 16 kW • 70 • 0.73 = 820 kVA
According to a)
S
n1
= 1.27 • 16 kW = 21 kVA
According to b)
S
n2
> S
n1
⇒ S
n2
is decisive.
The matching transformer requires a rated power S
n
of 25 kVA for a short-circuit voltage u
k
of 3%.
Example 2:
u
k
matching transformer = 1 %
S
K factory
= 50000 kVA
S
K line
= 16 kW • 70 • 0.73 = 820 kVA
According to a)
S
n1
= 1.27 • 16 kW = 21 kVA
According to b)
S
n1
> S
n2
⇒ S
n1
is decisive.
The matching transformer requires a rated power S
n
of 21 kVA for a short-circuit voltage u
k
of 1%.