YASKAWA VS-505WII - Page 12

MAINTENANCE (Cont'd )
3 . Place
the main circuit thyristor moduleon a
work bench . Remove the snubber board (4PCB-
U, V, W) mountingscrews (3 for
260
A
or below,
4 for 420 A or
more),
and
take out the snubber
board . (Fig . 18)
4 . Loosen the
fin mounting nuts alternately,
turning 1/4 turn at a time . Then, remove the
leaf spring .
5 .
Remove the fin and take out the leaf spring .
6 . Clean the contact surfaces of the new
thy-
ristor and the fin, and thinly coat
these surfaces
with joint compound,
JOINTAL Z madeby Nippon
Light
Metal Co ., Ltd .
7 . Align the
fin
locating
pin and the thyristor
locating hole, after making sure that the polarity
of the thyristor is correct .
8 . Keeping the leaf spring and the fin in paral-
lel, finger-tighten the clamping nuts .
Then,
tighten
them alternately through
1/4
turn at a
time, three times each with a socket wrench .
Now, the thyristor fin has been
installed
.
12
Thyristor Protective
Fuse Replacement
2 . Remove the two fuse
mounting bolts .
VS-505W
11, 230 V at 25 to 105 A, 460 V at 50 to
105 A
1 . Pull up the fuse blown indicating
microswitch
with the leads
connected .

(Fig .
19)
3 . Mount
the replacement fuse by reversing
the
removing procedure,
after checking it for model
and
capacity
.
9 . Tighten the snubber board mountingscrews
.
Then, mount
the
thyristor module by reversing
thedisassembling procedure, tightening the
screws firmly .
THYRISTOR
GATE (G)
CATHODE (K)
TERMINALS
FUSE
K (RED)
G (WHITE)
THYRISTOR
681-193
(a) With Thyristor Removed
Fig . 18 Thyristor Replacement
(b) Thyristor
Fig . 17 Main
Circuit Thyristor
(460 V, 420 A)
Fig . 19 Main Circuit
Fuse Assembly
(460 V,
105 A)