Fuse Sizes And Mounting; Special 2500A Fuse For Akru 50 - GE AKR-30 Series Maintenance Manual

SECTION 9-Fused Breakers
There are two types of fused breakers; AKRU 30, 800
ampere frame and AKRU 50, 1 600 ampere frame. Except
for the open fuse lockout device and the i ntegrally­
mounted fuses on the upper studs, the AKR U-30 and -50
breakers are identical to the u nfused AKR-30 and -50
models. Overcurrent trip devices are the same for both
types.
9.1 FUSE SIZES AND MO UNTING
Table 6 lists the range of fuse sizes available for these
breakers. The Class L fuses are mounted as shown in Fig .
5 1 . Other than the 800A size, which has a single mounting
hole per tang , each Class L fuse tang has two holes sized
-
for one half inc h d iameter bolts.
J
Class fuses rated 300 thru 600A have one mounting
hole per tang. The 300 , 350 and 400A sizes require copper
adapter bars per Fig. 52.
All V2-1 3 fuse mounting bolts should be torqued to 200-
350 in.- lb. The %-1 1 bolts whic h attach the C shaped fuse
adapters to the breaker studs should be torqued to 300-
525 in.-lb.
FIG. 51 - TYPICAL MOUNTING C LASS L
FUSES
9.2 S P ECIAL 2500A FUSE FOR AKRU-50
This fuse provides a melti ng time-current characteristic
that coordinates with 1 600A trip devices. Com pared physi­
cally with a 2500A N EMA Class L fuse, the special fuse is
more compact (shorter) ; its tangs are specially conf igured
and offset to achieve the required pole-to-pole fuse spac­
ing; a special primary disconnect assembly mounts directly
on the outboard tang of the fuse. Considering their unique
mounting provisions, when replacing these fuses the fol­
lowing procedure should be adhered to ( Refer to Fig. 53) :
a) Remove the primary d i sconnect assem bly from the
fuse tang, acco m p l ished by first loosening the two keys
via their holding screw and pulling them u pward and out.
After the keys are removed , pull the d isconnect assem bly
off the end of the fuse tang.
NOT E : This removal d o e s n o t disturb
disconnect's clamping force adjustment.
b) Remove the upper barrier.
c) Detach the inboard end of the fuse by removing the
two 1 /2 inch - 1 3 bolts. A ratchet and socket with a short
extension will be requied.
d) Remove the heat sink.
e) Remove the fuse.
f) I nstall the new fuse by reversing the disassembly
procedure. E nsure that the mating faces of the fuse and
heat sink are clea n .
�DAPTER BARS (COPPER)
FIG. 52 - 300 T H R U 600 AMP C LASS J
FUSE MOUNTING
the
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