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

SECTION 9-Fused Breakers
There are two types of fused breakers ; A K R U 30, 800
am pere frame and AKRU 50, 1 600 ampere frame. Except
for the open fuse lockout device and the i ntegrally­
mounted fuses on the u pper studs, the AKRU-30 and -50
breakers are identical to the unfused AK R-30 and -50
models. Overcurrent trip devices are the same for both
types.
9 . 1 FUSE SIZES AND MO UNTI NG
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 mo unting
hole per tang , each Class L fuse tang has two holes sized
for one-half inch diameter bolts.
J
Class fuses rated 300 thru 600A have one mounting
hole per tang . The 300, 350 and 400A sizes req uire copper
adapter bars per Fig. 52.
All 1f2-1 3 fuse mounting bolts should be torqued to 200-
-
350 in. lb. The %-1 1 bolts which 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 SPECIAL 2500A FUSE FOR AKRU-50
This fuse provides a melting 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 igu red
and offset to achieve the required pole-to-pole fuse spac­
i ng ; 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 pri mary d iscon nect assem bly from the
fuse tang, acco m pl ished by fi rst loosening the two keys
via their holding screw and pull ing them u pward and out.
After the keys are removed , p u l l the d isconnect asse m bly
off the end of the fuse tang.
NOT E :
This re m o va l does
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 req uied.
d ) Re move the heat sink.
e) Remove the fuse.
f) I nstall the new fuse by reversing the di sassembly
procedure. E nsure that the mating faces of the fuse and
heat sink are clean .
ADAPTER BARS (COPPER)
FIG. 52 - 300 TH R U 600 A M P CLASS J
FUSE MOUNTING
not disturb the
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