Operating Mechanism; Closing Spring Assembly; Closing Solenoid; Overcurrent Tripping Device - Westinghouse De-ion DB-15 Instructions Manual

OPERATING MECHANISM

The operating mechanism (see Fig. 5)
adjustable and consists of a series of steel links de­
signed to secure low closing and tripping forces.
To check for friction, raise the trip bar and slowly
rotate the manual operating handle in close and
trip direction. The linkage should follow the handle
without sticking.
The tripping load should not exceed 38 ounces
measured at the trip bar.

CLOSING SPRING ASSEMBLY

The closing spring assembly is shown in the
·breaker closed position in Fig. 5. Assuming the
breaker is in the open position, the following closing
sequence applies:
-
Rotating the closing handle clockwise raises the
link and lower spring guide to compress the
lift
closing spring. Near the end of the closing stroke
the top end of the lift link strikes the first toggle
lever to start the breaker closing. As the breaker
closes the push rod raises the toggle link and push
link out of toggle which permits the closing spring
to complete the breaker closing.
Slow emergency operation to check th� contact
sequence can be obtained by exerting a slight
closing pressure on the closing handle and simul-
taneously pushing forward on the bre ' a ker cross
bar to start fhe breaker closing.
Maintenance. Oil the pins and slides every
lO,QOO operations.

CLOSING SOLENOID

.
:
The closing solenoid (see Fig. 5) is non-adjustable.
It is designed for intermittent duty only. Check for
loose bolts.
The minimum permissible control voltages at the
terminal of the closing coil, and the closing currents
at nominal voltage are listed in Table No.2 on page 12.

OVERCURRENT TRIPPING DEVICE

The overcurrent tripping devices of the various
ampere ratings are of the same general construction
and size. They can be applied to the DB-15 circuit
breaker in ratings of 15 to 225 amperes and to the
DB-25 circuit breaker in ratings of 40 to 600
amperes.
The overcurrent tripping device can �asily be
removed from the breaker and replaced with another
unit of different rating without affecting the cali­
bration.
The overcurrent tripping device, normally fur­
nished for each pole of the circuit breaker, is de-
14
is
non­
FIG. 6. Overcurrent Tripping Device-Location
. si gned for service Qn motor or gener
feeder circuits or for service on systems 'where
selective overcurrent tripping is desired.
- � "c.7A and 7B shows time-current characteristics of
DB-15 and DB-25, circuit breakers equipped with
typical overcurrent tripping devices, for selective
tripping.
Construction. The overcurrent tripping device
is of the air delayed type with all elements adjust­
able. The adjustment knobs or parts likely to be
touched while making adjustments of time or pic�up
current are electrically insulated. Fig. 6A shows
a typical overcurrent tripping device ready for
mounting on . a breaker pole unit .
Loosening or removal of the reset valve requires
recalibration of the long delay scale.
Installation and Removal. To install an over­
current tripping device, first make sure the lower
end of the flexible conductor is in the recessed
pocket of the molded base directly above the lower
breaker stud. Then place the trip unit so that the
top terminal of the tripping device is over the
flexible conductor and the lower tripping device
terminal is over the lower breaker stud. Insert the
three bolts into the rear of the base and thread
them tightly into the terminals and molded base of
the tripping device.
shown in Table No. 3.
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The mounting bolt sizes are
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