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Type
50-DH-50
Air Circuit Breaker
STORAGE
The arcing chambers and barriers are shipped
separately from the breakers to guard against dam
age due to rough handling and for more secure pro
tection against dust and moisture.
The breaker is designed for indoor service and
should be put in a clean dry place immediately
upon arrival.
HANDLING, UNLOADING and UNPACKING
The shipment of a Type DH Air Circuit Breaker
requires careful handling and ample packing to
protect the breaker from serious shocks while in
transit. The breakers are completely assembled
and tested at the factory and are then dismantled
to permit the arcing chambers and barriers being
shipped separately.
Immediately upon receipt of a circuit breaker,
an examination should be made for any damage
sustained while enroute. If injury is evident or in
dication of rough handling is visible, a claim should
be filed at once with the Transportation Company
and the nearest Westinghouse Sales Office notified
promptly.
Unloading and uncrating the breaker requires
very careful work. The base of the crate to which
the breaker is fastened may be used as a skid in
moving the breaker around.
Do Not Use Lon�
Bars
to uncrate the breaker as they may slip
through the crating and damage the equipment, a
nail puller is recommended for that particular pur
pose. If a crane is available to use in removing
the breakers from the crates considerable time can
be saved in unpacking. Care should be exercised
in attaching the lifting hooks to the lifting holes in
the breaker frame to make certain that the chains
are not lowered too far as to become untangled in
some part of the breaker when the lift is made.
Approximate net weights:- Breaker Complete
520
lb., Arcing Chambers
20
lb. each, Interphase Bar
rier
15
lb.
INSTALLATION AND ERECTION
With the exception of the arcing chambers and
barriers, these breakers are shipped completely as
sembled and adjusted. No change in adjustments
should be required and none should be made un
less it is obvious that they have been disturbed.
However, before attempting to operate the break
er electrically it should be closed carefully by hand
to make certain that all parts are functioning
properly.
At this time it is well to check the contacts to
make certain that the settings have not been dis
turbed. The contact pressure adjustments are made
with the contacts in the closed position. The lower,
hinge contact, is adjusted by turning the nut two
thirds of a turn past the point where it becomes
snug. Pressure is secured on the upper contacts in
the earlier models by cup washers held in compres
sion by bolts and castle nuts, the castle nuts should
be turned up five-sixths of
a
turn after they have
7
first been made snug. In later models the upper cup
washer has been replaced with a conical spring and
spacer arrangement in which case the nut should be
turned up tight on the spacer and cottered in that
position. When adjusted in this manner the moving
contact blades will separate approximately -h inch
when the arcing contacts engage. There should be
a slight clearance between the arcing contacts when
the blades are in the fully closed position, this
separation is desirable to assure full pressure on
the main contacts.
A light film of graphite grease is applied to both
the arcing and main contacts before the breaker is
operated on the test floor. This film is removed
before shipment. Before the breaker is placed in
service the arcing contacts should be inspected to
see that they are free of oil. If the breaker is to be
used in an application requiring highly repetitive
operation a very light film of graphite grease ap
plied to the main contacts will prevent galling, how
ever, in such a case the film should always be suf
ficiently light so that none can work up onto the
arcing contact surfaces.
As the breakers are more easily handled with
the arc chambers removed it is advisable not to
mount the arc chambers and barriers on the break
er until the breaker has been installed in its perma
nent location, and all connections made, or in the
case of truck mounted breakers, until the metal
clad cells are ready to receive the removable units.
Before installing arc chambers inspect them to
make certain that the vents and slots are open and
free from foreign material. The arc chambers may
then be �ssembled by resting their supporting sur
faces on the pole faces of the magnetic circuit and
sliding them into position, using the pole faces as
a
guide. After the arc chamber has been placed in
position check to see that the contact blade of the
rear arcing horn in the arc chamber has engaged
the upper lead to the multi-turn coil. Connect the
shunt strap to the front horn in the arc chamber.
Check the tightness of the lower connection of
those shunt straps as they may have loosened dur
ing transit. The stacks may then be secured in
position by the non-magnetic retaining straps which
are bolted to the ends of the magnetic poles. The
breaker should then be closed slowly by hand to
check that there is no interference in the movement
of the moving contact blade.
The interphase barrier may then be bolted into
position.
OPERATION AND MAINTENANCE
Startin� Up
Before placing a breaker in service the power
lines as well as the control wiring should be
thoroughly tested for possible grounds and short
circuits that might have developed during the in
stallation period, also a final check should be made
on the various control circuits to make certain
that they were all operating correctly.
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