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i nner face of the stat i onary contact brush ret ai ner ( H ) .
support (K ) and the cont act d i al are as sembled together by means of a mount i ng s crew
( L ) and two l ock- n ut s ( M ) .
B arrel Contact
The d i rect i onal
overcurrent un i t , are shown i n F i g.
boun c i ng.
The stat i on ary contact ( G ) i s mounted on a fl at spi ral spr i n g ( F ) backed
up by a thi n d i aphragm (C ) .
A stai n l es s steel bal l ( B ) i s p l aced i n the tube before the d i aphragm i s as s embl ed.
When the mov i ng contact hi ts the stat i onary contact, the energy of the former i s
i mparted to the latter and thence to the bal l , whi ch i s free to rol l up the i nc l i ned
tube.
Thus the mov i n g contact come s to rest wi th substant i al l y no rebound or
v i brat i on.
To change the stat i onary contact mount i n g s p r i ng, remove the contact
barre l and s l eeve as a comp l ete un i t aft er l oos en i n g the screw at the fron t of the
cont act bl ock.
Un screw the cap ( E ) .
s pr i ng may then be removed.
TIME OVERCURRENT UNIT
The i n ver se t i me and very i n verse t i me overcurrent un i t s cons i s t of a tap ped
current operat i ng coi
coi l i s con nected to taps on the tap bl ock.
coi l s whi ch are connected i n ser i es wi th a d i rect i onal un i t contact.
f l ow i s i n such a d i rect i on as to c l ose the d i rect i onal un i t contacts, the shad i ng
coi l s act to produce a s p l i t -phas e fi e l d whi ch, i n turn, devel ops tor que on the
operat i ng d i sk.
The ext reme l y i nver se t i me overcurrent un i t i s of the wat tmetri c type s i mi l ar
to that us ed i n watt hour meters except as fo
structure has two conce ntr i c wi n d i ngs on the m i dd l e l e g of the magnet i c c i rcui t.
One of the s e i s a tapped current wi n d i ng con nected to taps on the tap bl ock; the
other i s a fl oat i ng wi nd i ng whi ch i s connected i n ser i es wi th the d i rect i on al un i t
contact s, a res i stor,
magnet i c c i rcui t.
un i t contact, the unit devel ops torque on the operat i n g d i sk.
The d i sk s haft carr i es the mov i ng contact whi ch comp l etes the tr i p c i rcui t when
i t touches the stat i onary cont act or contact s .
s pr i n g to gi ve the proper contact - c l os i n g current, and i t s mot i on i s retarded by a
permanent magnet act i ng on the d i s k to produce the des i red t i me character i s t i c .
v ar i abl e retard i ng force resul t i ng from
compensated by the s p i ral shape of the i nduct i on d i sk, whi ch resu l t s i n an i n creased
dr i v i n g force as the spr i n g wi nds up.
The torque cont rol c i rcui ts of both the t i me overcurrent and i n stantaneous
overcurrent un i t s
term i nal s are shorted together by i nternal l y con nected red jumper l ead s when the
rel ays l eave the factory ( s ee F i g.
des i red, these jumper l eads shoul d be removed.
G EK-49849
un i t contacts
( r i ght rear ) whi ch control the i n stantaneous
19.
The se are both mounted i n a s l i ght l y i n c l i ne d tube (A ) .
1
wound on a U-magn et i ron st ructure.
a
capacitor
and
When power fl ow i s i n such a d i rect i on as to c l ose a d i rect i onal
are wi red to term i nal s on the re l ay contact
t o
5
They are spec i al l y construct ed to s uppres s
The contact and i t s fl at s p i ral mount i ng
The U-magnet contai n s wound shad i n g
1 1
ows :
the upper port i on of the i ron
the two coils on the l ower l egs of the
The shaft i s restrai ned by a s p i ral
the grad i ent of the s p i ral s pr i n g i s
i n c l us i ve ) .
If extern al torque control i s
7
14
The stat i on ary contact
The t ap ped operat i n g
When power
bl ock.
The se
The
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