Siemens SINAMICS G130 Engineering Manual page 350

SINAMICS S120
Engineering Information
2nd measure: Use of an isolating transformer to reduce transient overvoltages in accordance with IEC 61800-5-1
The isolating transformer which is used quasi as standard to supply SINAMICS converters for virtually every type of
application reduces the overvoltage category III (for which the units are dimensioned) down to the overvoltage
category II. As a result, the requirements of the insulation strength of the air are less stringent. Additional voltage
derating (reduction in input voltage) is not necessary if the following boundary conditions are fulfilled:
·
The isolating transformer must be supplied from a low-voltage or medium-voltage network. It must not be
supplied directly from a high-voltage network.
·
The isolating transformer may be used to supply one or more drives or drive line-ups.
·
The cables between the isolating transformer and the S120 Infeed or Infeeds must be installed such that
there is absolutely no risk of a direct lightning strike, i.e. overhead cables must not be used.
·
Drives with Basic Infeed and Smart Infeed can be operated on the following types of power supply system:
§ TN systems with grounded star point (no grounded outer conductor).
§ IT systems (the period of operation with a ground fault must be limited to the shortest possible
time).
·
Drives with Active Infeed can be operated on the following types of power system:
§ TN systems with grounded star point (no grounded outer conductor, no IT systems).
The measures described above are permissible for the following drive line-ups with SINAMICS S120 Chassis.
They must be applied to all Chassis and system components of the drive line-up:
·
Drives with Basic Infeed on all voltage levels (380 V – 480 V 3AC and 500 V – 690 V 3AC).
·
Drives with Smart Infeed on all voltage levels (380 V – 480 V 3AC and 500 V – 690 V 3AC).
·
Drives with Active Infeed on voltage level 380 V – 480 V 3AC
(Measures for drives with Active Infeed for 500 V – 690 V 3AC on request).
SINAMICS Engineering Manual – November 2015
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Ó Siemens AG