Fuses; Calculation Example - ABB ACS800-04 Hardware Manual

86

Fuses

gG and aR fuses for protection against short-circuit in the input power cable or drive
are listed below. Either fuse type may be used if it operates rapidly enough. Choose
between gG and aR fuses according to the table under
between gG and aR fuses
the short-circuit current of the installation is at least the value given in the fuse
table. The short-circuit current can be calculated as follows:
where

Calculation example

Drive:
• ACS800-04-0260-3
• supply voltage U = 410 V
Transformer:
• rated power S
• rated voltage U
• transformer impedance z
Supply cable:
• length = 170 m
• resistance/length = 0.112 ohm/km
• reactance/length = 0.0273 ohm/km.
Technical data
U
I =
k2-ph
2
R + (Z
2 ·
c
I = short-circuit current in symmetrical two-phase short-circuit (A)
k2-ph
U = network line-to-line voltage (V)
R = cable resistance (ohm)
c
2
Z = z · U /S = transformer impedance (ohm)
k k N N
z = transformer impedance (%)
k
U = transformer rated voltage (V)
N
S = nominal apparent power of the transformer (kVA)
N
X = cable reactance (ohm).
c
= 3000 kVA
N
= 430 V
N
= 7.2%.
k
2
U
N
·
Z = z · = 0.072
k k
S
N
on page 91, or verify the operating time by checking that
2
+ X )
k c
2
(430 V)
= 4.438 mohm
3000 kVA
Quick guide for selecting