Siemens SINAMICS S120 Manual page 44

System overview
2.11 Derating data
Use of an isolating transformer to reduce transient overvoltages according to IEC 61800-5-1
As a consequence, overvoltage category III is reduced to overvoltage category II – which in
turn reduces the demands placed on the insulating capability of air. An additional voltage
derating (reduction of the input voltage) is not required if the following secondary conditions
are maintained:
● The isolation transformer must be fed from a low-voltage supply or a medium-voltage
● The isolation transformer may supply one or several Line Modules.
● The cables between the isolation transformer and the Line Module or Line Modules must
● The following line supply types are permissible for drives equipped with Basic Line
● The following line supply types are permissible for drives equipped with Active Line
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supply and must not be directly supplied from a high voltage supply.
be routed so that a direct lightning strike is completely ruled out, i.e. cables must not be
routed outside.
Modules and Smart Line Modules:
– TN line supplies with grounded star point (no grounded phase conductor).
– IT line supplies (operation with a short circuit must be restricted to the absolutely
shortest possible time).
Modules:
– TN systems with grounded star point (no grounded outer conductor, no IT systems) for
installation altitudes of greater than 2000 m.
Cabinet Modules
Manual, 03/2013, A5E03263538A