Arrangement Of Motor Modules Along The Dc Busbar - Siemens SINAMICS G130 Engineering Manual

Fundamental Principles and System Description
Engineering Information
With this connection variant, the Motor Modules are connected to the DC busbar by means of a switch disconnector
with fuses and a contactor with precharging device (precharging contactor with precharging resistors). The switch
disconnector and the contactors must be wired up in a 2-pole arrangement.
Electrical connection of a Motor Module to the DC busbar
Fast semiconductor fuses ensure short-circuit protection in the case of short circuits in the electrical coupling
assembly. 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 Modules.
The electronics of each Motor Module controls the precharging contactor and the contactor. The precharging device,
comprising precharging contactor and precharging resistors, enables the Motor Modules to be switched on or off
individually at any time while the DC busbar is energized.
As precharging contactors DC contactors must be used, as it may be necessary to disconnect the maximum possible
precharging DC current in the event of a fault. This scenario arises, for example, if a defective Motor Module with a
short circuit in the power unit is connected to the DC busbar. In this case, a precharging DC current of the magnitude
needs to be reliably controlled and disconnected by the precharging contactor.
As contactors, either DC contactors or, under certain boundary conditions, AC contactors can be used.
When low-cost AC contactors are used, no-load switching is an essential requirement. For this reason, the gating
pulses for the IGBTs in the Motor Modules must be disabled (pulse inhibit) when the Motor Modules are connected or
disconnected. Since no-load switching is a requirement, the system must be engineered to ensure that the contactor
cannot drop out in operation, i.e. the control voltage for the disconnector coil must be supplied by a reliable source
such as an uninterruptible power supply (UPS).
1.8.2.2

Arrangement of Motor Modules along the DC busbar

The SINAMICS S120 Motor Modules can be arranged on the DC busbar according to two basic principles:
·
Arrangement according to the power rating (power rating-related sequence).
·
Arrangement according to the position of the drives in the production process (process-related sequence).
SINAMICS Engineering Manual – November 2015
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I = V / (2 • R
Precharging DCLink
)
Precharging