Series Overcurrent Tripping Device Ec-2, Ec-2A, Ak-50; Long Time-Delay And High-Set Instantaneous Tripping; Instantaneous High-Set Tripping; Time-Adjusting Indexing - GE AK-2-50 Maintenance Manual

Low Voltage Power Circuit Breakers GEK-7303
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SERIES OVERCU~RENT TRIPPING DEVICE EC-2~ EC-2A, AK-SO
The Type EC-2, EC-2A, (see Fig. 29) over- case, which ~ay be taxen off without disturbing
current tripping device is available in three forms: the trip unit itself. ·
1. Dual overcurrent trip, with long- time delay
and high- set instantaneous tripping.
2.
Low-set instantaneous tripping.
S.
High-set instantaneous tripping.
The dual trip has adjustable long-time and
instantaneous 12ick-up settings and adju~table time
settings. Both · forms of instantaneous trip have~
adjustable pick-up settings.
LONG TIME-DELAY
AND HIGH-SET INSTANTANEOUS
TRIPPING
(Fig. 29) .
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By means of the adjustment knob (3), whicb
can be manipulated by hand, the current pick-up
point can be varied from 80 to 160 percent of the
series coil rating. The indicator and a calibration
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plate (2) on the front of the case provide a means
of indicating the pick-up point setting in terms of
percentage of coil rating. The calibration plate is
indexed at. percentage settings of 80, 100, 120,
1140, and 160.
· As in the case· of the EC-1 over- current trip,
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the long-time delay tripping feature can be supplied
with any one of three time-current characteristics
which correspond to the NEMA standards max-
imum, intermediate and minimum long-time delay
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operating bands. These are identified as lA,
lB and 1 C characteristics, respectively. Ap-
proximate tripping time for . each of these, in the
same order are 30, 15, and 5 seconds at 600
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percent of the pick-up value of current. (See
time-current characteristic curves, Fig. 42).
The tripping time may be varied within the
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limits shown on the characteristic curves by turn-
ing the time adjustment screw (4). Turning in a
clockwise direction in(?reases· the tripping time;
counterclockwise O).Otion decreases it. The dashJ?Ot
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arm (8) is index~d at four . points, MIN- 1/3-2/3-
MAX, .as _ indicated in Fig. 30. When the index
mark on the connecting link(9)linesupwith a mark
on the dashpot arm, the approximate tripping
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time as shown by the characteristic curve is
indicated. The lA and lB characteristic devices
are shipped with this setting at the 2/3 mark and
the 1 C characteristic at the 1/3 mark. The stand-
ard characteristic curves are plotted at these same
settings.
Time values are inversely proportional to the
effective length of the dashpot arm. Therefore, the
linkage setting that gives the shortest time·value
is the one at which dimension ·
11 A",
Fig. 29; is
greatest. The time adjustment screw (4) may be
turned by inserting a Phillips head screwdriver
through the hole in the front of- the case.
If
it is
desired to relate the linkage setting to the index
marks on the linkage it will be necessary to re-
move the case. This may be done by removing
the two mounting screws, one on each side of the
If the breaker is provided with a shunt trip
ox:. undervoltage device, the EC- 2, EC- 2A, . c ase on
the center pole must be taken off first before the
cases on the outer poles can be removed.
INSTANTANEOUS LOW-SET
TRIPPING
{Fig. 2~) .·
The low-set instantaneous pick-up point may
be varied by the adjustment knob
(3).
The calib-
ration in this case usually ranges from 80 percent
to 250 percent of the series coil rating, with
the calibration plate indexed at values of 80,
100, 150, 200, and 250 p~rcent of the rating.
INSTANTANEOUS HIGH-SET
TRIPPING
Fig. 29)
The high-.set instantaneous pick-up value may
have one of the following three ranges: 4 to 9 times
coil rating; 6 to 12 times coil rating or 9 to 15
time coil rating. The pick-up setting may be varied
by turning the instantaneous pick-up adjusting
screw (12).
Three calibration marks (15) will appear on
the operating arm (14) and the value of these
calibration marks will be indicated by stampings.
on the arm as follows : (4X - 6.5X - 9X) or (6X -
9X - 12X) or (9X - 12X - 15X). .
At the · f actory, the pick-:-up point has been set
at the nameplate value of the inst~taneous trip
current. (Usually expressed in times the ampere
rating of the trip coil.) The variation in pick-
up setting is accomplished by varying the tensile
force on the instantaneous spring (5). Turning
the adjustment screw changes the position . of the
movable nut (11) on the screw. The spring is
anchored to this movatile nut so that when the
position of the nut is changed, there is a corres-
- ponding change in the spriI?g load. As the spring
is tightened, the pick-up point is increased.
Fig. 30 (417A464) Time- adjustment indexing