296 Technical data
■
Calculating the short-circuit current of the installation
Make sure that the short-circuit current of the installation is at least the value
given in the fuse table.
The short-circuit current of the installation can be calculated as follows:
I
=
k2-ph
2
2 ·
R
c
where
I k2-ph
Short-circuit current in symmetrical two-phase short-circuit
U
Network line-to-line voltage (V)
R c
Cable resistance (ohm)
Z k = z k · U n 2 / S n = transformer impedance (ohm)
Z k
z k
Transformer impedance (%)
U n
Transformer rated voltage (V)
S n
Nominal apparent power of the transformer (kVA)
X c
Cable reactance (ohm)
Calculation example
Drive:
•
ACS580-01-145A-4
•
supply voltage = 410 V
Transformer:
•
rated power S
rated secondary voltage (supply for drive supply) U
•
•
transformer impedance z
Supply cable:
•
length = 170 m
•
resistance/length = 0.398 ohm/km
•
reactance/length = 0.082 ohm/km.
U
2
+ (Z
+ X
)
k
c
= 600 kVA
n
= 7.2%
k
= 430 V
n