Siemens Sinamics S120 Manual page 143

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
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
u = short-circuit voltage of the matching transformer in %
k
(must be between 1% and 3% for Active Line Modules and Smart Line Modules)
S
K
Danger to life through electric shock as well as fire hazard due to overcurrent protective
devices that trip too late
Overcurrent protective devices that do not trip or trip too late can cause an electric shock or
fire.
• To protect personnel and for fire protection purposes, at the infeed point, the system
Supplementary condition
Limitation a)
The rated power of the matching transformer S
the rated power P
S
n1
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 plant
least the following values.
S
K line
S
K line
Booksize Power Units
Manual, (GH2), 04/2014, 6SL3097-4AC00-0BP6
, S = calculated rated power of the transformer resulting from a) and b)
n2
= short-circuit power.
WARNING
fault level and loop impedance must correspond to the specifications in the
documentation in order for the installed overcurrent protection devices to trip within the
specified time.
of the Line Module.
n
≥ 1.27 • P
n
) and that of the matching transformer at the connection point (S
≥ 70 • P (for Active Line Module and Smart Line Module)
n
≥ 30 • P (for Basic Line Module)
n
Line connection and line-side power components
or S ), this can lead to increased line voltage dips and
n k
must always be a factor of 1.27 higher than
n1
3.11 Line connection variants
) must reach at
K line
143