Technical data
115
Quick guide for selecting between gG and aR fuses
The table below is a short cut in selecting between gG and aR fuses. The
combinations (cable size, cable length, transformer size and fuse type) in the table
fulfill the minimum requirements for the proper operation of the fuse.
The following parameters can affect the correct operation of the protection:
• cable length ie, the longer the cable the weaker the fuse protection, as the long
cable limits the fault current
• cable size ie, the smaller the cable cross-section the weaker the fuse protection,
as the small cable size limits the fault current
• transformer size ie, the smaller the transformer the weaker the fuse protection, as
the small transformer limits the fault current
• transformer impedance ie, the higher the z
k
the weaker the fuse protection as
high impedance limits the fault current.
The protection can be improved by installing a larger supply transformer and/or
bigger cables, and in most cases by selecting aR fuses instead of gG fuses.
Selection of smaller fuses improves the protection, but may also affect the fuse life
time and lead to unnecessary operation of the fuses.
In case of any uncertainty regarding the drive protection, please contact your local
ABB representative.
Fuses (UL)
UL class T or L fuses for branch circuit protection per NEC are listed below. Fast
acting class T or faster fuses are recommended in the USA.
Check from the fuse time-current curve that the operating time of the fuse is
below 0.1 seconds. The operating time depends on the supply network impedance
and the cross-sectional area and length of the supply cable. The short-circuit current
can be calculated as shown on page 112.
Drive type
ACS850-04…
Cable type Supply transformer minimum apparent power S
N
(kVA)
Copper Aluminum Maximum cable length with gG
fuses
Maximum cable length with aR
fuses
10 m 50 m 100 m 10 m 100 m 200 m
-430A-5 2 x (3x120) Cu 3 x (3x95) Al 530 570 670 370 370 370
-521A-5 3 x (3x95) Cu 3 x (3x150) Al 660 720 840 500 570 760
-602A-5 3 x (3x120) Cu 3 x (3x185) Al 660 720 840 520 570 760
-693A-5 2 x (3x240) Cu 3 x (3x240) Al 880 980 1200 580 670 880
-720A-5 3 x (3x150) Cu 3 x (3x240) Al 880 980 1200 610 670 880
Note 1: The supply transformer minimum power in kVA is calculated with a z
k
value of 6% and
frequency 50 Hz.
Note 2: The table is not intended for transformer selection - that must be done separately.
00556489 A
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