I V
S TAT I C
OVE RCURRENT TR I P
D E V I C E
A .
I NTRODUCT I ON
T h e
A l l i s -Cha l me r s
St a t i c
O v e r cu r re n t T r i p
Dev i ces
a r e
c�n p l e t e l y s ta t i c ;
t h a t
i s
t h e re a re
n o
movi ng
pa r t s o r con t ac t s .
The
c i r c u i t s of t h e dev i ce a re
des i gned
f o r
l i gh t
l
o
a d i
n
g
of
compone n t s a nd a rL
t empe r a t u r e compens a te d fo r a c c u racy a nd s t a b i l i ty
of
ca l i b ra t i on ove r w i de
t empe r a t u re
r a nges
f o r i nd e f i n i t e p e r i ods of t i me .
The s t a t i c ove rcu r re n t
t r i p dev i ces . wh i ch r e p l ace
t he
e l ec t ro -mechan i ca l s e r i es ove r cu r r e n t t r i p
d e v i c e s . pe r f o rm the s ame f u n c t i on w i
t
h
a
h
i
g
h
e r d e g ree o f acc u r a cy and
ve r s a t i. l i ty .
I n c ommon w i t h s e r i e s · over c u r r en t t r i p d ev i ces . a l l e nergy
for ope ra t i on
I s
ob t a i ned f rQn ove r l oa d or fa u l t c u r ren t .
No
ba t t e r i e s or
o t h e r ex t e rna l powe r sou r ces a r e requ i red ,
The
comp l e t e
s ta t i c
o
v
e
r
cu r r e n t t r i p s y s tem cons i s t s
of
t h ree
c u r r e n t t ra n s
f o rme rs , one p e r pha s e , moun t ed o n t h e c i r cu i t b re a k e r p r i ma ry c o n n ec t o r s ,
a
re l ea s e ma g ne t , a n d the s t a t i c ove r c u r r e n t t r i p d ev i ce , Th i s s y s t em
op
e
ra
t e
s
to
t r i p
t he
c
i
r c u
i
t b r eake r
when
a s ys t em ove r l oad cond i t i on
exce ed�
a
p re - s e l ec t ed va l ue of cu r re n t .
T r i pp i ng w i l l
oc c u r
a f t e r a p r ed e t e rm i n ed
t i me d e l ay
o r
i ns t a n t a n eous l y depend i ng upon the adj us tme n t
s e l ected
and t h e
ma g n i t ude
of t h e
ove r l oad .
The
s ta t i c
t r i p dev i ce
con t a i ns t h ree
cu r r e n t
t rans forme rs
wh i ch p r ov i de a
�ma l l
l ow v o l t a ge s econda ry c u r ren t p ropor t i ona l t o
t he
c i r cu i t b r eake r
pr i ma ry c u r r en t .
The
s econda r y of each t ra n s f o rme r i s connec t e d i n s e r i e s
w
i
t
h
a
powe r s u pp l y t ra n s f o rme r and a n a ux i l i a ry t ra n s f orme r .
Th e o u t p u t
of
t h e
powe r s u pp l y t r a n s f o rm e r s i s rec t i f i ed t o p r ov i de
D . C .
ene r g y t o
t h e
r e l ea s e mu gne t t r i p co i
1
a n d a l s o
a
re
g
u
l
a
t
ed
D . C .
powe r s up p l y t o ope ra t e
t rans i s t or
c i rc u i t s .
Pote n t i ome t e r s o r rheos t a t s con nec ted i n pa ra l l e l w i t h
t h e a ux i l i a ry t ra n s f o rme r s p r ov i de a n A . C . s i gna l vo l t a ge p r o po r t i on a l t o
the
p r i ma ry c u r ren t .
Th i !>
ac t s
a s the i n te l l i gence i np u t f o r t h e dev i ce ,
u n d t he mu gn i t u d e o f t h i s
A . C .
v
o
l
t
a
g
e de t e rm i nes whe t h e r
o r
n o t t he b r e a �c r
w i I I t r i p a n d t he t i me d e l ay
b e f o r e
t r i p p i n g . The re l a t i on
between
th i s A . C .
S i !Jild l vo
l t
a
g
e
and
the
p r
i
m
a
r
y c u r r e n t c a n
be
v a r i ed b y
adj us t i n g the
po t e n t i ome t e r s
t o s e t
the
1n i n i mum
p r i ma ry
c u r r e n t a t
wh i ch
t
r i pp i
n
g
w i l l
oc cu r .
T h i s i s
th�
p i c k - u p
adj ustme n t .
A t ra ns i s to r t r i gge r c i r cu i t p reven t s opera t i on o f
the t t rn t n g
c
i
r
c
u
i
t
un l es s
t h e s i g n a l exceeds
95%
o f
p i c k-up
v a l ue .
I f t h e t r i gge r has ope r a ted , a
capac i to r w i l l cha rge y ra d u a l l y
io
a v o l t a ge wh i ch caus es t h e s t a t i c
sw i t �h
to
o�e r a t e , ene r g i z e t he
t r i p
c o i l ,
and
t r i p
t h e b r ea ke r ,
l f a t a ny
t
i
me
b e f o r e
th e s t a t i c
swi tch
a c t ua l l y ope ra t es ,
t h e
p r i ma r y c u r r e n t d e c r e a s e s to
95%
o r
l c s :,;
o f
t he
s e t
p i ck-up , t he
t r i g g e r w i l l t u r n o f f
D
n
d
r e s e t
\'l i l t
t u ke
� l .::.. u � .
5 orut.! m i nc.r
va r i a t i ons i n p i c k - up
a nd
t i me
de l a y may be
expe c t ed
w i t h
t empe ra t u re
f l u c t ua t i ons
f r om an amb i e n t o f
-4o°C .
t o
a n amb i en t
o
f
5 5°C .
A
t y p i ca l b reake r r a t i n g p l a t e
i
s
s hown
i n
F i gure
7A .
The
ma
x
i m
u
m
r a t ed
ampe res
i s
d e t e rm i ned
by
t he c u r ren t
t rans f o rme rs mou n t e d on t h e
c i r c u i t
b r.:: a kc r pr i ma ry connec to r s .
The
max i mum
c u r ren t
ava i l ab l e
i s l i m i t e d b y
t he
c i rc u i t b
r
e
a
k
e
r
f rame s i ze . S i n c e t h e s t a t i c ov e r c u r ren t t r i p
dev i ce
componen ts
art:!
ca I
i b r a t cd
i n t e rms o f
t ra ns f o rmer
s econd a ry c u r r en t . t h e s an.e
dcv i
ce c a n b
e
u� ed
w i t h any o f
the
g r oups of c u r ren t t r a n s f o rme rs ava i l a b l e .
- I I -
Summary of Contents for LA-1600
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