Siemens sinamics dcp - Page 341

Operation
7.11 Closed-loop control
SINAMICS DCP
Operating Instructions, 09/2019, A5E34382853K
339
Figure 7-70 Limiting the reactor current in the overvoltage range of a 120 kW device
Example for the 120 kW device
1)
:
– Assumed values:
U
S1
= 600 V (rated voltage)
U
S2
= 850 V (operation in the overvoltage range)
– Side 2 is the side with the higher voltage; as a consequence, the following is obtained
from the diagram above:
I
max, reactor
= 116.7 A
– Side 1 is the side with the lower voltage. As a consequence, the current on this side
corresponds to the reactor current; however, due to the voltage on side 2, is limited to
I
max, reactor
.
– Therefore, in this operating state the device only provides a maximum power of:
P
max
= U
S1
× I
max, reactor
= 600 V × 116.7 A = 70 kW
– This is the reason that side 2 can only be operated with a maximum current given by:
I
max, S2
= P
max
/ U
S2
= 70 kW / 850 V = 82.35 A
1)
Conversion losses were not taken into account in this example.