SECTION 1 5-EC Trip Device {Cont.)
1 5.2 SERIES OVERCURRENT TRIPPING
DEVICE EC-1
Each series overcurrent tripping device is enclosed in a
molded case and mounted by screws and a bracket to the lower
part of the pole unit base.
Refer to
Fig . 1 23
for the discussions below.
1 5.2.1
SHORT TIME-DELAY TRIPPING
The armature (7) is restrained by calibrating spring (8). After
the magnetic force produced by an overcurrent condition over-
2
9
8
7
Left Side View Showing
Short Time Delay Mechanism
comes this restraining force, the armature movement is further
retarded by an escapement mechanism which produces an in
verse time delay characteristic. The mechanism is shown on
Fig.
1 23
1 5.2.2 LONG TIME-DELAY TRIPPING
The armature
(1
0) is restrained by the calibration spring
( 1 1
)
.
After the magnetic force produced by an overcurrent condition
overcomes this restraining force, the armature movement is fur
ther retarded by the flow of silicone oil in a dashpot, which prr:>
duces an inverse time delay characteristic. The mechanism is
shown on
F
i
g
.
1 23
1 0
I I
1 2
13
20
Right Side View Showing
Long Time Delay Mechanism
Front View Showing
Mounting Bracket
1 .
Series Coil
8. S.T.D. Calibration Spring
1 5. Plunger
2. Magnet
9. Trip Paddle Adjusting Screw
1 6.
Cylinder
3.
Pallet
1 0 . L.T.D. Armature
1 7.
Calibration Plate
4.
Pinion
1 1 .
L.T.D. or Low-set lnst. Calibration Spring
1 8. Trip Paddle
5. Escape Wheel
1 2. lnst. Trip Spring (High Set)
1 9. Trip Arm
6.
Driving Segment
1 3.
Spring Holder
20. Clamping Bracket
7. S.T.D. Armature
1 4.
Calibration Clamp Nut
FIG.
1 23 -
SERIES OVERCURRENT TRIPPING DEVICE EDC-1
87
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