Direct Acting Tripping Device; Short Time-Delay Tripping; Long Time Delay Tripping; Instantaneous Tripping - GE AK-2-50 Maintenance Manual

GEK-7303 Low Voltage Power Circuit Breakers
UNDERVOLTAGE LOCKOUT DEVICE.
3
4
5
6
7
· · TYPE AK-50, 75
&
100 . . .
Fig. 25 (8039985) .Right side view of mechanism
- frame Breaker shown in open position.
1. Mechanism cam ··
2. Undervoltage lockout arm
3. Undervoltage lockout lever
4. Undervoltage device armature
5. Undervoltage cjevice.
6. · Undervoltage lockout spring
7 •. Mechanism frame
with the addition of the lockoutfeature. The lockout
feature consists of arm (2), lever (3), and spring (6).
The lockout linkage is activated by the movement of
the mechanism cam (1). When the breaker is closed,
the undervoltage device is defeated by the lever (3)
holding the armature (4) in the closedairgap posi-
tion. When the breaker opens, the mechanism cam
moves down, allowing spring (6) to rotate arm (2)
clockwise which causes lever (3) to rotate counter-
clockwise to release armature (4) allowing the
undervoltage device to operate normally.
DIRECT ACTING TRIPPING
DEVICE EC-1 B
(Fig. 26)
(USED ON AK-2-75 AND AK-2-100)
. The type EC-lB overcurrent tripping device is
a direct-acting device that causes the power circuit
breaker with which it is associated to open within
a predetermined time range which .depends upoq:
the magnitude . of the current overload. The
EC-lB tripping device can be constructed to s·upply
a variety of different types of time-current charac- ·
teristics, either alone or in combination. These
are long time delay, short time delay, and instant-
aneous, and they are identifred respectively
by
numbers 1, 2 and 3. Characte1'istics are further
broken down within each of the first two of these
general classifications into maximum, intermediate
and minimum values of the time delay period. These
are coded resDectivelv ..as ·
AA. Bl,3 and. CC. Tjme
and current .relationships for the various device
characteristics are given by curve drawing
2
89B 198.
· The EC- ll:3 is adjustable on high-s_ et instan-
taneous tripping. The adjustable setting mechanism
of the EC-lB is shown in Fig. 26.
Low-set · instan~aneous tripping is adjustable
Irqm bO· percent to 250 percent of the ·continuous
current rating of the device. · Whenever this is
used, it is the only characteristic of the device.
Instantaneous tripping used in conjunction with
any other characteristic is always high-set.
. When armature (1 or 22) closes ag.ainstthe mag-·
net (11), motion is transmitted through the mech- ·
anism linkage, rotating tripping
link
(8) so that
connecting rod (10) is pulled towards .. the rear of
the breaker. · By means of trip paddle (14) this
results in the displacement of the breaker mech-
anism trip · latch which causes - the breaker to
trip open • . Long and· short time delay trippi!lg
is achieved through separate timing devices as
described below:
SHORT TIME~DELA Y TRIPPING
. (Fig. 26) .
The short time delay armature (1) is restrain-
ed by a calibration spring (6).
If
the force tending ·
to close the armature against the magnet (11)
is great enough to overcome the spring force,
_ the speed of movement is governed by the mechani-
cal escapement mechanism _ cons_ i sting of parts
(2>, (3), (4) and (5). . · .
LONG TIME DELAY .TRIPPING .
(Fig. 26)
The long time delay armature
(22)
is restr:µned
by- the long time delay calibration spring (15).
After the. magnetic force produced by the over-
current condition overcomes this restraint, .the
velocity of the armature movement is governed
by the flow of oil through an orifice in the piston
6f the dashpot (17). The time required to displace
the piston is inversely proportional to· the force
tending to close the magnetic circuit.
INSTANTANEOUS TRIPPING
(Fig. 26)
High-set, Non-adjustable
When an overcurrent is of the magnitude of the
instantaneous trip setting, the magnetic force
generated is great enough to extend the instant-
eous spring (21), tripping the breaker- instantly.
. If
the . overcurrent is below this . value, the heavy
instantaneous · spring acts as· a link, transmitting
the force to the other control elements. ·
If
the
device has only the instantaneous characteristic,
the front end· of ~pring (21) is hooked onto a pin
fastened on the frame. ·
.
.
High-aet, Adjustable-EC-1B
Adjustable instantaneous tripping is accomplish-
ed by varying the amount of tensile force on the