Westinghouse DK-15, Manual

Page: 50 / 96

Type
DK- 1 5 and DK-25 Air Circuit
Breaker
The mechani sm crank engag e s a hardened s t eel cam on the rol ler
le ver . The relat i ve mo t i on of the crank roller wi th respe c t to thi s cam
surface i s to produ ce the max imum mechani cal advan tage when the c l o s ing
l oad i s great e s t . A limi t swi t ch s egment on the mechan i sm crank shaft
posi tively carries the crank r ol l er p a s t the cam af t er a c l o s ing op eration ,
s o tha t the br eaker can b e c l o s ed ei ther manual ly o r e l e c tri cally wi thou t
interferenc e or me chan ical di s engagement . The only requirement i s that the
limi t swi t ch mu s t be allowed to cu t off the motor c l o s ing curr ent .
One adjus tment between the motor me chan i sm and the br eaker rol ler
lever should be checked for proper operati on . Cl o s e the br eaker manua lly
and rotate the motor by hand . Thi s ·i s done by removing the pla te at the
l o�er end and rotating the armature in the di rec t i on of the arrow , un t i l
the crank roller i s j u s t pas s ing over the heel of the cam . There should b e
from
1/64
to
1/32
inch c l earan ce b e tween the ro ll er surface and the cam
surface at thi s p o in t . If b inding oc curs, the minimum c l o s ing vol tage will
be unduly high , and i f too much clearance i s pr e s ent , the me chani sm may
fa il to move the breaker toggle l i nkage t o the c omplet ely cl o s ed p o s i t i on .
Thi s adjustmen t i s ma in tained by adding or taking out a spa c er between the
molded t i ebar and the c a s t roller lever on the right s i de .
The mo tor c l os ing current is g iven in the fo l l ow ing tab l e f o r
s tandard c ontr o l v o l ta ge ra t ings :
Vol tage Ra ting
110
Vol t , A- c .
220
Vo l t , A- c .
125
Vol t ,
D- e .
250
Vol t ,
D- e .
Shunt
Trip
Attachment
Cl o s i ng Curr ent
a t Normal Vol tage
30
Amperes
15
Amp er e s
30
Amperes
15
Amperes
The s hunt trip a t tachment, w hen supp lied , i s mounted rigidly to
the breake r frame behind the fa ce p la te . The trip bar bra cke t is a t tached
t o i t s lowe r end . 'When the shunt trip i s no t supp lie d , i t s p lace is taken
by a long trip rod he ld by a ca se
identica l in out s ide appearance w i th the
shunt trip ca se . Both type s are inte rchangeable and can be readily removed
and replaced . In re plac ing the shunt trip a s s embly, make sure the moving
c ore and trip rod a s sembly is fre e to move without b inding a ga ins t the guide
hole-s or c o il .
The shunt trip i s de s i gn ed for i n t ermi t t ent duty . The tripping
curr en t mus t always be cut off by an auxi liary swi tch on the breaker . The
norma l tripp ing curren t s for s tandard c ontrol vol tages ar e :
Vol tage Rating
110
V ol t , A- c .
220
Vo l t , A- c .
125
V o l t ,
D- e .
250
Vol t ,
D- e .
Wiring Diagram
Tripping Curr ent
7
Amp eres
4
Amp er e s
2 . 5
Amperes
1 . 5
Amperes
The s tandard wiring diagram for the motor me chan i sm and shunt
trip a t tachmen t s are gi ven in Fig .
10 .
The mo tor c on trol circui t can be
supp l i e d with a special r elay as an integral part of the e l e ctri cally oper­
ated br eaker that preven t s r e c los ure un t i l after the ext ernal control
swi t ch has been opened . S ee Fig .
8 .
Thi s pr events the br eaker from pumping
if c l o s e d agains t a high ov erl oad or shor t circui t . A further feature of
the c ontrol wiring i s the preven t i on o f e l e c tr i c ally inching the breaker
c l o s ed after the moving c ontact a s s emb ly has s tarted to c l os e .
4
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