Siemens SINAMICS G130 Engineering Manual page 101

Fundamental Principles and System Description
Engineering Information
Precharging with G130 and G150 converters via a separate precharging rectifier and precharging resistors
The principle of precharging involves the use of ohmic resistors and is, therefore, subject to losses. This means that
the precharging resistors must be thermally dimensioned to support precharging of the DC link for their G130 or
G150 converter without becoming overloaded. Additional DC link capacitances cannot be precharged. For this
reason, other S120 Motor Modules, for example, must not be connected to the DC link of a SINAMICS G130 or G150
converter. Complete precharging of the DC link is only permitted every 3 minutes.
In the case of Basic Line Modules for the SINAMICS S120 modular system equipped with thyristors, the DC link is
charged via the rectifier thyristors by changing the firing angle (phase angle control). During this process, the firing
angle is increased continuously for 1 second until it reaches the full firing angle setting. This precharging principle
results in hardly any losses, which means that an extremely high DC link capacitance could be precharged. The
permissible DC link capacitance for the connected inverters (S120 Motor Modules), however, must be limited to
protect the thyristors against an excessive recharge current entering the DC link capacitance when the voltage is
restored following a line voltage dip. Despite this, the limit for the permissible DC link capacitance is relatively high
due to the robust line-frequency thyristors.
The maximum permissible DC link capacitance for the different S120 Basic Line Modules can be found in the section
"Checking the maximum DC link capacitance" of the chapter "General Information about Built-in and Cabinet Units
SINAMICS S120".
Precharging with S120 Basic Line Modules equipped with thyristors via phase angle control of the thyristors
In the case of Basic Line Modules for the SINAMICS S120 modular system equipped with diodes, precharging is
carried out via resistors, which create losses. To precharge the DC link, the rectifier is connected to the supply
system on the line side via a precharging contactor and precharging resistors. Once precharging is completed, the
bypass contactor is closed and the precharging contactor is opened again. Due to the power losses that occurs in the
resistors during precharging, the DC link may be completely precharged only every 3 minutes and the permissible DC
link capacitance of the connected inverters (S120 Motor Modules) is limited to lower values than in the case of Basic
Line Modules with thyristors.
The maximum permissible DC link capacitance for the different S120 Basic Line Modules can be found in the section
"Checking the maximum DC link capacitance" of the chapter "General Information about Built-in and Cabinet Units
SINAMICS S120".
Precharging with S120 Basic Line Modules equipped with diodes via precharging contactor and precharging resistors
SINAMICS Engineering Manual – November 2015
101/528
Ó Siemens AG