Design Guide | iC7 Series Air-cooled System Modules
In an IT system, filter losses in a single phase ground fault depend on the setup. All capacitances to ground should be minimized
to minimize the fault current. The fault current increases the losses, and continuous operation during the ground fault cannot be
guaranteed, especially if the filter is already in the limits without the fault. The filter has temperature protection against too high ground
fault currents.
If drives are connected in parallel, the recommended common connection point for motor cables is at the motor terminals. See
Recommended Installation of Motor Cables
7.3
LCL Filter
The LCL Filter is used with the AFE module, and it ensures correct power quality and minimal interruption to the grid. Each AFE power
unit has its own LCL Filter. The LCL Filter is designed for the nominal AFE switching frequency. It is safe to increase the switching
frequency, but decreasing the switching frequency below the nominal value increases the risk of overheating and unwanted resonances.
An increased switching frequency leads to derating of the AFE module. See
10.7 Derating the Output Current
.
NOTICE
Use aR-type AC fuses with the LCL Filter. Select the fuses according to the frame and the current rating of the system module.
When designing the fuse installation, refer to the wiring diagrams of the AFE modules.
7.4
The Pre-charging Unit
The pre-charging unit is used for the pre-charging of the system modules that are connected to the same DC bus. There are 3 electrical
sizes and an IEC and an UL variant of these. The pre-charging unit is available as an accessory.
e3
0b
k5
47
.1
0
1
2
Figure 38: Pre-charging Units
1
Pre-charging unit, IEC
2
Pre-charging unit, UL
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