64
Instruction Booklet IB 33-790-1J
Effective November 2010
Instructions for Low Voltage Power
Circuit Breakers Types DS and DSL
EATON CORPORATION www.eaton.com
Fig. 67 Undervoltage Trip Device.
8.7.1 Undervoltage Trip Attachment
The undervoltage trip shown in Figure 67 is an electro-
mechanical device that trips the circuit breaker when the
voltage on its coil falls to between 30 and 60 percent of
normal. The standard unit trips instantaneously. A similar
device is also available with non-adjustable time delay
intended to ride through momentary fluctuations of sys-
tem voltage.
In operation, a moving core is normal
ly held magnetically
against a stationary core and a spring. This is linked to a
latch carrying a roller which restrains the main tripping
lever of this assembly.
When the coil voltage is reduced sufficiently, the torsion
spring overcomes the magnetic attraction between the
two cores. The moving core travels upward, and rotates
the latch in a counterclockwise direction so that the roller
moves from beneath the tail of the main tripping lever.
A
torsion spring (not visible in Figure 67) around the pivot
pin of the tripping lever then rotates it in a counterclock-
wise direction, causing a projection on the right side of
this lever to strike a pin in the breaker mechanism trip
shaft, and rotate the latter in a clockwise direction to trip
the breaker.
Fig. 68 Undervoltage Trip Device Operation.
As the breaker opens, a pin on the left pole unit shaft
strikes a vertical leg (Reset arm) of the undervoltage trip
-
ping lever and rotates it counterclockwise against its tor-
sion spring. Another arm on the tripping lever resets the
roller latch and the moving core. A slight amount of over-
travel on the trip latch insures positive resetting under all
conditions. Set Figure 68 for the relationship of the und-
ervoltage trip device, pole shaft and trip shaft.
Always connect the undervoltage coil on the line side of
the breaker unless the attachment is equipped with a
time delay device
. In this case, the time delay will delay
tripping of the breaker long enough to permit energization
of the undervoltage coil from the load side. Do not use an
auxiliary switch contact in this circuit.
8.7.2 Overcurrent Trip Switch
This device is available as an optional accessory on
either manually operated or power-operated breakers of
all ratings. Its function is to provide a signal to indicate
that the breaker has tripped open by action of the Amp-
tector trip
unit due to phase or ground overcurrent. Nor-
mal tripping by the trip plate, shunt trip device,
undervoltage trip device, etc. does not cause it to oper-
ate. It is mounted on and operates from the trip actuator
of the breaker.
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