3
CFW-11M RB |3-9
Installation and Connection
0 0.2 0.4 0.6 0.8 1
1.2
1.4
t
0.4 s
t
0.6 s
Figure 3.12 -
Current during the pre-charge
Table 3.6 -
Sizing of the pre-charge
Peak current during the pre-charge (A)
0,82∙(Vline/R)
Energy stored in the capacitor bank (J)
400 V line
N∙0.04∙Vline
2
600 V line
N∙0.02 Vline
2
Pre-charge duration (s)
400 V line
0.09∙N∙R
600 V line
0.04∙N∙R
Where R is the ohmic value of the resistor used for each phase and N is the number of power units.
NOTE!
;
N corresponds to the total number of power units: the CFW11M RB power units plus the output
CFW11M power units which are fed by the CFW11M RB.
;
In case the CFW11M RB is feeding other converter, WEG must be consulted.
E.g.:
The following values are obtained with an converter composed by three power units at the CFW11M RB
input and three power units at the CFW11M output, where the input line voltage is 380 Vrms (400 Vline):
- N = 6.
- Energy stored in the capacitor bank: 6∙0.04∙(380)
2
= 34656 J.
- By using three 20 Ω resistors (one per phase), each resistor must withstand 11552 J.
- The resistor manufacturer should be able to inform the power supported by the component.
- The peak current during the pre-charge would be 15,5 A and the pre-charge duration would be of
10.8 s.
