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Characteristics of Thermal-Magnetic Dual Overload
The general
with invers e
t ime de lay charac ter i s t i c s in Fi g .
s e tt ing of the pointer on the s c a l e
un i t and tha t value of current w i l l j u s t
3 0
minu t e s
or l onger in a normal
thumb s crew t ownrd the
curr ent in minm:;e s t ep s as d e s i red .
Amb i en t c orre c t i on i s explained in F i g . 3 as
b ra t i on for each 2 o c .
for 2 4 o c . amb i ent , but if it i s
i s t i c s o f
Fig .
5
be s e t at approx imat ely
The cali b ra t i on adju s tment can therefore
normal running
current o f the
t emperature ,
frequency of s tarting , e t c .
f orded under a l l c ondi ti on s o f opera t i on .
Ful l deta i l s f or
ne t i c trip a t t achment are explained in F i g . 3 .
Replacement of Overload Attachments
B o th type s of overl oad trip uni t s may be eas i ly r emoved . From the
rear , take out two s crews that fa s t en the magne t a s s emb ly to the main pane l
and di s c onne c t the trip uni t upper
p o l e uni t shunt s e c t i on .
and large nut mus t al s o b e removed .
plac ement i s s imply the rever s e o f thi s pro c edure .
Af ter the uni t i s s e curely mounted t o the pane l , only one ad jus t
m en t i s n e c e s s ary f or c orre c t operat i on wi th t h e breaker .
c on s i s t s of s e t t ing the s crew in the
to pr operly
trip the breaker
magne t , as exp lained in Figs . 2 and 3 .
Electric Closing Mechanism
,
El e c tri cally operated
ent i re ly s el f - c on tained
s i de of the breaker frame .
t o a c curately l o cate the m e c hani s m in s�lating bas e . B y r em oving three b o l t s
thi s c ompl e t e a s s embly can be taken o f f the breaker without di s engaging any
par t s ex c e p t the wiring .
The c l o s ing
shaft mot or wi th
las t the l i fe of the
motor s haft and the
the upper end of the
Thi s gear a s s embly i s
of norma l s erv i c e .
grea s e from running down int o the motor winding s .
The mot or i s de s i gned t o d e v e l op an exc ep t i onal ly hi gh t orque f or
i t s s i z e ,
and i s ther e f or e rated f or interm i t t en t s ervi c e .
frequently than onc e e very 3 minu t e s
i s c l o s ed more
motor may o verheat .
l ower end - b e l l of the motor
v o ltage,
and t o pr event
has cut off the motor curren t .
DK- 1 5
DK-2 5
Type
and
arrangement of thi s
amb i ent t emperatur e .
150%
cal ibra t i on s e t t ing rai s e s the minimum tr ipping
r i s e in t emperature .
d e s ired to mee t the calibra t i on c harac t e r
at 4 o o c . , f o r i n s tan c e , the c al ibrati on ad j u s tment should
108%
for m inimum tripping at normal current rat i ng .
m o t or as i s de s ir e d ,
a d j u s tment and maint enan c e
In the c a s e o f
wi th a thin spa c er b etween the
DK
c ir cui t
mot or me chan i sm
Two of the t oggle l i nkage p i n s s er v e as dowel s
motor i s a
s ingle pha s e
ball b ear ings
s ea l e d wi th
apparatus .
A s ingl e
me chan i sm crank i s a c c omp l i shed w i th a worm mounted on
motor shaft engaging a worm
lub r i cated on a s s embly
An o i l s eal on the
A c entri fuga l s p e ed l imi t ing dev i c e i s bui l t i n t o the
to pr even t ex c e s s i ve s p eed at normal and over
c oa s t ing o f the
Breaker
Air Circuit
attachment i s
7 .
pla t e i s the normal rat ing of the trip
trip the b r eaker i n approx imately
The at tachment i s
b e s e t a s c l o s e t o
C ompl e t e pro t e c t i on i s thus af
t erminal where i t i s b ol ted t o . the main
drawout s tuds the f inger c lu s t er
The trip uni t may now b e removed .
out er end of the
break er s are
11 )
( fi g .
moun t e d on
c ommu ta t or type ,
lubri cant that w i l l
redu c t i on o f sp eed
g ear on the crank s haft .
suffi c i en t for s everal y ear s
motor s haft
me c hani sm a f t er the l im i t swi t ch
3
F i g . 3
shown in
100%
The
calibrat i on
Adjus tment of the
1%
i n c rea s e in c a l i
cal ibra ted
depending o n
amb i ent
of the therma l - mag
Thi s ad jus tment
trip armature lever
armature and
equ ipped with
the
r i ght
v er t i cal
normally
be tween the
preven t s any o i l
If the breaker
f or l ong p er i ods , the
the
R e
a n
or
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