Active Infeed - Siemens SINAMICS G130 Engineering Manual

SINAMICS S120
Engineering Information
6.5.3

Active Infeed

In the case of SINAMICS S120 Active Line Modules with associated Active Interface Modules, which are available as
S120 Chassis (air-cooled and liquid-cooled) and S120 Cabinet Modules, the DC link is precharged by a precharging
circuit with resistors in the Active Interface Modules, a process which incurs heat losses. To precharge the DC link,
the Active Interface Module with associated Active Line Module is connected at the line side to the line supply via a
precharging contactor and precharging resistors. Once the DC link is precharged, the bypass contactor is closed and
the precharging contactor opened again.
SINAMICS S120 Active Infeed: Precharging by means of precharging contactor and precharging resistors
IMPORTANT:
It is absolutely essential that the precharging contactor and the bypass contactor are controlled by the internal
sequence control of the S120 Active Line Module (precharging contactor via connector -X9:5,6 and bypass contactor
via connector -X9:3,4). When a circuit breaker is used as the bypass contactor, it is essential that breaker opening is
controlled by an instantaneous release. For this reason, only circuit breakers equipped with instantaneous
undervoltage release may be used.
For S120 Active Line Modules in Chassis format with associated Active Interface Modules in frame sizes FI and
GI, precharging circuit and bypass contactor are integral components of the Active Interface Module. The precharging
circuit in the Active Interface Module is designed short-circuit-proof and does not require an external fuse protection
by the customer.
For S120 Active Line Modules in Chassis format with associated Active Interface Modules in frame sizes HI and JI,
the bypass contactor is not an integral component of the Active Interface Module. In this case, the bypass contactor
must be provided externally by the customer, and also the fuse protection for the precharging circuit must be
provided externally by the customer. The fuses recommended for this purpose are listed in the table below.
Owing to the brief period of overlap when the precharging contactor and the bypass contactor are closed at the same
time, it is essential to ensure that the precharging circuit has the same phase sequence as the main circuit.
For S120 Active Line Modules with associated Active Interface Modules in Cabinet Modules format, the
precharging circuit either does not require fuse protection (because of a short-circuit-proof design in the Active
Interface Modules of frame sizes FI and GI), or fuse protection is provided as standard inside the Line Connection
Module which is connected in series upstream of the Active Line Module with associated Active Interface Module.
The following table specifies the rms values of the line currents which occur at the beginning of the precharging
process in the case of line supply voltages 400 V or 690 V. Due to the principle of precharging using resistors, the
specified values apply irrespective of the DC link capacitance to be precharged. Where other line voltage values
apply, the line currents must be converted in proportion to the line voltage.
The specified precharging currents decay according to an e-function until the precharging process is completed after
a period of typically 1 to 2 s. Due to the temperature rise in the precharging resistors during the process, the
minimum permissible interval for complete precharging of the DC link is 3 minutes.
SINAMICS Engineering Manual – November 2015
361/528
Ó Siemens AG