Siemens SINAMICS S120 - Page 145

Line connection and line-side power components
3.11 Line connection variants
Booksize Power Units
Manual, (GH2), 07/2016, 6SL3097-4AC00-0BP8
145
Example 3:
If S
K factory
is smaller, the transformer must be stronger.
u
k
matching transformer = 3 %
S
K factory
= 3000 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 34 kVA for a short-circuit voltage u
k
of 3%.
Example 4:
If S
K factory
is lower, you can use, alternatively to example 3, a transformer with a lower u
k
.
u
k
matching transformer = 1%,
S
K factory
= 3000 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%.
Note
S
n2
for the matching transformer can be reduced by reducing u
k
. In the examples above, the
power drawn from other loads has not bee
n taken into account.