Construction; Installation And Removal; Operation - Westinghouse DE-ION DB-75 Instructions Manual

The overcurrent tripping device can be re­
m oved from the breaker easily and replaced
w ith another unit of the same or different
r ating without affecting the calibration of
the units involved.

Construction

The mounting frame casting supports the
two sub-assemblies of the trip unit.
upper part of the frame are the two magnetic
a rmatures a nd their associate d links a nd
brackets.
mounting frame is the moldarta box which con­
tains the calibration springs, time delay ele­
m ents and calibration knobs.
held to the mounting frame by two long screws
at the bottom of the calibration box.
Installation and Re moval
CAUTION:
TRIPPING DEVICE, BE SURE THAT THE BREAKER IS
IN THE OPEN POSITION AND DE-ENERGIZED
To remove an overcurrent tripping device
from the breaker, loosen the two captive bolts
at the bottom of the mounting frame (L-3) un­
til they turn freely.
bolts at the top of the mounting frame while
supporting the trip unit so that it doe� not
fall. These two bolts clamp a slotted angle
mounting bracket and merely have to be loos­
ened; they do not have to be removed from the
mounting frame.
to be removed from the breaker by lowering it
down behind the breaker platform.
T o ins tall a tripping device on a breaker,
first make certain that the breaker is open
and is not connected to live circuits.
loosen the upper mounting bolts on the trip
u nit so that the bolts can slide into the
slotted mounting brackets on the stationary
yoke.
b ottom of the breaker, sliding it up behind
the mechanism platform.
c aptive mounting bolts,
completely.
that the gaps between the tapered portions of
the main armature are a p proximately equal
when the main armature is closed. Then tighte n
all four mounting bolts securely.
I. B.
35- 240-1
Fastened to the lower part of the
BEFORE REMOVING OR INSTALLING A
Then loosen the two
The trip unit is then free
Then install the trip unit from the
Start the bottom two
but do not tighten
Next, align the trip unit so
TYPE DB-75
Adjustment of Trip Screw
The trip screw mounted on the trip finger
must be adjusted properly to obtain proper
tripping.
CAUTION:
TRIPPING THE BREAKER, CARE MUST BE TAKEN TO
KEEP FINGERS AND FACE AWAY FROM ALL CONTACT
On the
ARMS AND OPERATING LINKAGE.
the adjustment,
the bottom o f the calibration b o x counter­
clockwise to the stop so that the trip unit
is set for minimum time delay.
the breaker and carefully reach under the
This box is
mechanism with both hands and push the lower
armature fully closed with the thumbs.
it closed for at least the minimum long delay
t ime (20 to 4 0 seconds) .
t rips,
tripping finger until the breaker just barely
trips.
make sure that the breaker is in the o pe n
p osition.
trip screw at which the breaker just trips,
turn the screw exactly one full turn in the
direction to trip the breaker sooner.
to make sure that the breaker will trip when
either armature is closed if long and instan­
taneous type trip units are used, or when
both armatures are closed if . l ong and short
delay type trip units are used.
delay armature is for timing only.
it alone will not trip the breaker.

Operation

STANDARD OVERCURRENT T RIPPING DEVICE
(Refer to Figure 7A)
When a small, overload current flows through
Then
the breaker pole unit conductor (R) . it causes
the moving armature
the stationary core (A) .
armature is retarded by the diaphragm (D) whose
motion is in turn controlled by the amount of
air admitted by the long time delay valve (F) .
After a time delay, determined by the setting
of valve (F) , the armature will have rotated
the trip crank
breaker by moving the trip lever (K) .
this type of tripping, the compression spring
(C) is not compressed beyond its normal length.
DE-ION AIR CIRCUIT BREAKER
SINCE THIS ADJUSTMENT INVOLVES
To proceed with
turn the long time dial a t
If the b re ak e r
reset the screw at t h e e nd o f the
Before re-adjusting the trip screw,
After finding the position of the
(B)
to be attracted toward
The motion of the
(J)
far enough to t ri p the
Then close
Hold
Check
The short
Closing
During
15