SECTION 1 5-EC Trip Device (Cont.)
1 5.4
REVERSE CURRENT TRIPPING DEVICE
The device is enclosed in a molded case and is mounted on
the right pole base similar to the series overcurrent tripping
device.
The reverse current tripping device
(see Fig . 1 25)
consists of
a series coil (2) with an jron core mounted between two pole
pieces (9), also a potential coil (7) connected across a constant
source of voltage and mounted around a rotary-type armature
(1
0).
Calibration spring (6) determines the armature pick-up
when a reversal of current occurs.
As long as the flow of current through the breaker is in the
28
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normal direction, the magnetic flux of the series coil and the
magnetic flux of the potential coil produce a torque which tends
to rotate the armature counterclockwise. The calibration spring
also tends to rotate the armature in the same direction. This
torque causes the armature to rest against the stop screw ( 1 2)
attached to a bearing plate on the right side of the device.
If the current through the series coil (2) is reversed, the ar
mature (1
0)
tends to move in the clockwise direction against the
restraint of the calibration spring (6). When the current reversal
exceeds the calibration setting, the armature revolves clockwise
causing the trip rod (3) to move upward engaging the trip paddle
(1 ), thereby tripping the breaker.
12
1 .
Trip Paddle
2.
Series Coil
2A. Adjusting Nut
28. Locking Nut
3.
Trip Rod
4.
Trip Crank
5.
Setting Sealing Screw
6.
Calibration Spring
7.
Potential Coil
8.
Calibration Nut
9.
1 0.
1 1 .
1 2.
1 3.
1 4.
Pole Pieces
Armature
Counter Weight
Stop Screw
Mounting Screw
Screw
FIG. 1 25
ED-1 REVERSE CURRENT TRIPPING DEVICE
89
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