Fuses; Calculation Example - ABB ACS800-U7 Hardware Manual

116

Fuses

The drive is equipped with aR fuses as standard. Standard aR fuses and optional gG
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
and aR fuses
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:
• ACS800-07-0260-3
• supply voltage U = 410 V
Transformer:
• rated power S
• rated voltage (drive supply voltage) U
• transformer impedance z
Technical data
on page 120,
U
I =
k2-ph
2
2 · R + (Z
c
I = short-circuit current in symmetrical two-phase short-circuit
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
= 7.2%.
k
Quick guide for selecting between gG
or verify the operating time by checking that the short-
2
+ X )
k c
= 430 V
N