GE AK-1-15 Instructions Manual page 21

FIg. 17 Type E«:-I Series Overcurrent Tripping hvlce
21
.1Ql1' SIll( VIEt SMOIIUI;
U1lGTMoaATlIIfDUlIllliM
IO--Jlj....-:i~
I I--'--llt..,.;
1?---lII:--,f-Ij\l
~=~,
13---;A+-I-~ '--t<=---=41
SELECTIVE TRIPPING
Selective overcurrent tripping is the applica-
, tion of circuit breakers in series so that only the
circuit breaker nearest the fault opens. Anyone Or
combination of two or more of the preceding over-
current devices maY 'IJe used
m
a selective system.
The breaker having the shorter time setting and
lower pickup will trip before the breaker having
the longer setting allldhigher pickup, provided the
fault is on the part of the line protected by the
breaker having the lower setting.
In
order to reduce the possibility of damaging
the equipment and to provide. maxbnum' safety to the
operator, the overload caused by a famt is removed
in a minimum amount of time by selective tripping.
Overloads producing current which is less than the
short time delay pickuP are removed in a matter
of a few seconds, while currents
in
excesS
of
this
value are removed
in
a fraction of a second.
For the exact characteristics and setting of
each breaker in a selective system, reference
should be ma,de to the coordination chart furnished
for the particular system.
~==~20
Air
Circuit Breakers Type AK-1-1l5 and AK-1-25
GEH-1807
~~-9
1Il:--IlI--
8
~1I--7
-+r;::~\
I
v-t-ItlI--6
'Vf;~lt:--5
4
1. Seriell CbU
6. Driving Sepent 11. L.r.D. Calibration SprihK 16. Cylinder
2;
~8gnet
7.
8.!l'.D. Mlll8ture
12. Ihlltantaneoull Trip Spring
17. calibration Plate
3. Pallet
8. S.r.D.
CaHbratiOn Spring
13.
Spring
Holder 18. Trip Padd.l.e
4.
PiniOn
9.
Trip Paddle Adjusting Screw
14.
Calibration'C1&mp Nut
19.
Trip Ana
5. Escape 1heel Ilh L.1'.D. Al'1IIature 15. Plunger 20. d8lllPing Bradtet
LONG TIME DELAY TRIPPING, FIG. 17
WTSIOEVlflStlOIIMG
ImT TIlE DElAT IlItiC:MMISIII
'.. The 'armature
(10)
is retained by the calibra-
tion spring
(11).
After the magnetic force, produced
bY an overcurrent condition, overcomes this re-
8\I'aining force, the armature movement is further
retarded by the flow of silicone oil in a dashpot,
which produces an inverse time delay characteristic.
The mechanism is shown in the right side view of
Fig. 17.
INSTANTANEOUS TRIPPING, FiG.
17
,
,
(a) Adjustable instantaneous tripping takes place
after the magnetic ,force produced by an
overcurrent condition, overcomes the re-
straining force of the calibration spring
which can be adjusted by the calibration
clamp nut (14). ,
(b) Nonadjustable instantaneous tripping takes
place after the magnetic force produced by
an overcurrent condition overcomes tne '
restraining force of a nonadjustable spring.