Siemens SINAMICS G130 Engineering Manual page 121

Fundamental Principles and System Description
Engineering Information
All the DC link capacitance connected to the DC busbar is precharged by the precharging circuit of the SINAMICS
S120 Infeed. When the drive configuration is engineered, therefore, it is absolutely essential to check whether the
Infeeds precharging circuit is adequately dimensioned. For further information, please refer to section "Checking the
maximum DC link capacitance" in chapter "General Information about Built-in and Cabinet Units SINAMICS S120".
When directly connected to the DC busbar, all Motor Modules are supplied with DC voltage as long as the SINAMICS
S120 Infeed is in operation. With this connection variant, it is not possible to switch Motor Modules on or off
selectively, i.e. the complete drive configuration must be switched on or off.
Electromechanical connection to the DC busbar by means of a switch disconnector
For some applications, it may be necessary to disconnect the Motor Modules separately from the DC busbar. This
might be necessary in cases where special safety requirements need to be fulfilled, e.g. visible isolating distances
during servicing, or where plant sections need to be switched on or off as required. For such applications, the
modules must be connected to the busbar by means of separable contact points.
A switch disconnector is used to provide an electromechanical connection between the Motor Module and the DC
busbar. The disconnector must be wired up in a 2-pole arrangement.
Electromechanical connection of a Motor Module to the DC busbar
If the Motor Modules to be connected are equipped with integrated, fast semiconductor fuses (such as the air-cooled
Motor Modules in Chassis format), these internal fuses provide protection against internal short circuits. Therefore,
with Motor Modules of this type, the switch disconnector does not need to be fitted with any additional fuses which
means that the switch disconnector can be fitted with bar conductors.
If the Motor Modules to be connected do not feature integrated fuses (such as the liquid-cooled Motor Modules in
Chassis format), the switch disconnector must be fitted with fast semiconductor fuses, which will provide protection in
the case of internal short circuits.
These fuses are not required to protect the Motor Modules against overload, as overload protection is already
realized by the control electronics of the Motor Module.
All the DC link capacitance connected to the DC busbar is precharged by the precharging circuit of the SINAMICS
S120 Infeed. When the drive configuration is engineered, therefore, it is absolutely essential to check whether the
Infeeds precharging circuit is adequately dimensioned for the maximum possible number of Motor Modules
connected to the DC busbar. For more detailed information, refer to section "Checking the maximum DC link
capacitance" in chapter "General Information about Built-in and Cabinet Units SINAMICS S120".
With the electromechanical connection variant, individual Motor Modules may only be switched on or off when the DC
busbar is de-energized. It is not possible to switch individual Motor Modules on or off during operation due to the
absence of a precharging device, i.e. the Motor Modules can be switched on or off only when the power supply to the
entire system is disconnected and the DC link is de-energized.
Electrical connection to the DC busbar by means of a switch disconnector and a contactor assembly
If the application requires individual Motor Modules to be switched on and off selectively while the plant is in
operation, e.g. in order to disconnect defective Motor Modules from the live DC busbar, to connect standby units or
reconnect repaired units, the electrical connection must be made using a contactor assembly including precharging
device.
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Ó Siemens AG