Westinghouse DB-75 User manual

.,.' . .;
Instructions for
Types DB-75, DB - 100 and DBF-40
Air Circuit Breakers
600 Volts A·C
250 Volts D·C
Continuous Cu r rent Rating
DB-75 DB - 100
2,000 Amperes 4,000 Amperes
2,500 Amperes 5, 000 Amperes l D·C
3,000 Amperes 6,000 Amperes ~ Only
Westinghouse Electric Corpo rat ion
Switchgea r Division, East Pittsb u rgh, Pa.
J. B. 33-8S()4& SE, Effective September, 1976. Supersedes J.B. 33-8S()4& SD, November, 1966.
1- ··.
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2
TABLE OF CONTENTS
Par t One RECEIVING, HANDLING
AND STORING
Page 7
Inspection. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Storing.... ....... ..... ..... ......... . ................................. 7
Pa rt T wo
INSTALLATION
Pages 8- 11
Connections. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Enclosur
es. .. .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Part Three
MAINTENANCE
Pages 12-24
Pole Unit. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Contacts ......................... . ........................... . ...... 14
Maintenance
of Contacts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Operating Mechanism. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Closing Solenoid. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Overcurrent Tripping Device. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Description. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Construction. . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Installation and Removal. .. .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . 18
Adjustment of Trip Screw. . .. . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Standard Overcurrent T ripping Device. . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Selective
Overcurrent Tripping Device. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Instantaneous Overcurrent Tripping Device (Single Element). . .. . . . . . . . . . 22
Time-Current Characteristics. .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22
Calibration. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Ma.
intenance. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Control Relay. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Inspection. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Maintenance. .. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Shunt Trip Attachment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Inspection. .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24
Maintenance. .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Undervoltage Trip Attachment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Undervoltage Time Delay Attachment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Inspection. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Maintenance. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Auxiliary Switch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Inspection. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Maintenance. . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 )
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TABLE OF CONTENTS (Continued)
Part Three MAINTENANCE (Continued)
Pages 24-30
Alarm Switch Attachment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Inspection. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Maintenance. . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Electric Lockout Attachment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Inspection. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Maintenance. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Key Lock Attachment. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Inspection. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Maintenance.. . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Key Interlock Attachment. . .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Inspection. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Maintenance.. .... ... .... ....... .... .. ..... . .......... .. ·. . . . . . . . . . . . . 30
Rectifier Unit for A-C Undervoltage and A-C Electric Lockout Attachments. . .. . 30
Inspection. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Maintenance. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Reverse Current Trip Attachment. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Inspection. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Maintenance. . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Field Discharge Switch. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Recommended Spare Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3
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4
LIST OF ILLUSTRATIONS
Fi gur e
Page
1 DB-75 Outline and Mounting Dimensions . . . . . . . . . . . . . . . . . . . . . . 9
IA DB-100 Outline and Mounting Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
lB DBF-40
Outline and Mounting Dimensions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
IC DB-75 Outline and Mounting Dimensions. . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2 Typical
Wiring Diagrams. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3 Cross-Sectional View of DB-75
and DB-100 Circuit Breakers .. . . . . . . . . . . . . 15
3A DB-75 and DB-100 Three Position Operating Mechanism.. . . . . . . . . . . . . . . . 16
4 Adjusting Limits of Main
and Arcing Contacts for DB-75 and DB-100 Cir-
cuit Br eakers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5 Closing Solenoid-Construction Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6 Cross-Sectional View of
Overcurrent Tripping Device with Long Delay and
Instantaneous Elements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7
Schematic and Typical Time-Current Characteristics of Over cu rrent Tr ip -
ping Device with Long Delay and Instantaneous Elements. . . . . . . . . . . . . . . . 20
8 Cross-Section al Vi ew of Overcurrent Tripping Device with Lo ng Delay and
Short Delay Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8A Selective Overcurrent Trip Operations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
9 Schematic and Typical Time-Current Characteristics of Overcurrent Trip-
ping Device with Long De lay and Short Del ay Elements . . . . . . . . . . . . . . . . . 23
lOA Schematic Diagram of Overcurrent Tripping Device with Instantaneous
lOB
11
12
13
14
15
16
17
18
19
20
21
Element
Only. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Typical Time-Curr en t Cha racteristics of Over cu rrent Tripping Device with
Instantaneous Element Only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Control Relay-Construction Details . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Shunt Trip Attachment-C onstruction Details . . . . . . . . . . . . . . . . . 26
Undervoltage Trip Attachment-Construction Details. . . . . . . . . . . . 27
Und ervo ltage Time Attachment-Construction Details. . . . . . . . . . . . . . . . . . . 28
Auxiliary Switch-Construction Details . . . . . . . . . . . . . . . . . . . . . . . .. . 28
Alarm Switch Attachment-Construction Details. . . . . . . . . . . . . . . . 29
Electrical Lockout Attachment-Construction Details. . . . . . . . . . . . . . . . . . . . 29
Key Lock or Key Interlock Attachment-Construction Details. . . . . . . . . . . . . 30
Rectifier Unit for A-C Undervoltage and Electrical Lockout Attachments. . . . 31
Re
verse Current Trip Attachment-Types "D B-75" and "DB-100" Air
Circuit Breakers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Cross-Section View of Field Discharge Pole Unit . . . . . . . . . . . 33
·-.
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l.B. 33-850-4 ll& 5
"DB" AIR CIRCUIT BREAKERS
WESTINGHOUSE
TYPE ''DB'' AIR CIRCUIT BREAKERS
Type "DB" air circuit breaker is designed to give continuous and reliable
service
as the protective link between the power source and associated pro-
ductive equipment. This
breaker is built to operate with a minimum of main-
tenance, while
at the same time its simplified construction permits maximum
accessibility for inspection
and adjustment when required. The ease with which
attachments
may be added or removed is an outstanding feature of the " DB "
design.
For
the greatest measure of safety to operating personnel and also to min-
imize maintenance requirements, the breaker sh o uld be mounted in an enclosure
suitable to local operating conditions. A selection
of standard enclosures is
available for various applications.
•
Important: To assure proper functioning, inspect each breaker at reg-
ular intervals in accordance with a systematic maintenance schedule.
The frequency and character of the inspections will for the most part
be determined by the severity of the duty performed. The minimum
requirements, however, should consist of a light monthly inspection,
with a thorough inspection semi-annually. Occasional checks on cali-
bration as well as on coordination and freedom of all moving parts,
must be included in the maintenance schedule. Consult Westinghouse
engineering and service personnel for recommendations pertaining to
special operating or maintenance conditions .
5
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~ - -
6
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PART ONE
1.8 . 33-850-4 & 5
"DB" AIR CIRCUIT BREAKERS
RECEIVING, HANDLING AND STORING
TYPES "DB-75" AND "DB-100" AIR CIR-
CUIT BREAKERS are shipped in wooden crates
with all attachments moun t ed in place.
Important: To avoid damage to the break-
ers, do not use hooks in handling.
Table No. 1
NET WEIGHTS OF 3 POLE BREAKER
DB-75
DB-100
DBF - 40
475 lbs (Add 50 lbs for D.0.)
525 lbs (Add 75 lbs for D.0.)
550 lbs (Add 75 lbs for D.0.)
Immediately upon receipt, examine shipment for
any loss or damage incurred during ·shipment. If
injury or rough handling is evident, file a damage
claim at once with the transportation company and
notify the nearest Westinghouse Sales Office.
When unpacking, be sure that no loose parts
are missing or left i~ the packing material. Report
all shortages
at once. Blow out any dust or particles
of packing material that
may have accumulated on
the circuit breaker parts.
INSPECTION
The "DB" breaker assembly consists of a co-or-
dinated group of sub-assemblies mounted on a sup-
porting
panel. The complete breaker assembly is to
be mountedwith the panel in a vertical position. All
inspections for
proper operation should, therefore,
be made with the breaker in this position. Final in-
spection should preferably
be made with the break-
er in its permanent mounting.
Inspect
the breaker as follows:
1. Lift
trip finger by hand to make sure that it
does not bind.
Z. Remove any foreign particles from the hinge
end of the moving contacts.
3. Insert the maintenance operating handle and
slowly close the breaker.
a. Observe whether all parts are in proper
alignment and move freely.
b. Be sure that the contacts are clean and
properly aligned. The center finger of the stationary
arcing contacts should have a slight lead.
c. The hinge end of the moving contact is
lubricated with
graphite grease and is therefore
black. For a description of contact alignment
refer
to "CONTACTS", Page 14.
4. If the contacts are in alignment and all parts
move freely, continue
the closing until the breaker
is latched.
5. Hold the maintenance operating handle down.
Push the "Push to Trip" button to trip breaker.
a. The toggle li,nkage should collapse and the
moving contact assembly move freely to
the full
open position. This should be followed by complete
resetting of
the links in the toggle mechanism as
the handle is raised.
h. The links must alwaysbe free to move with·
out friction
or binding.
6. Check the attachmentsfor operation in accord-
ance with the appropriate instructions as given
under "Maintenance", Part III of this book.
Note: It is not advisable to lubricate any
parts of the breaker. The lubrication supplied
during factory assembly is sufficient for years
of service. The lubricant is of a special form
which is used sparingly. The addition of oil
will only promote the accumulation of dust
and dirt.
STORING
If circuit breakers are not to be installed in their
permanent locations at once, they should be care-
£ully inspected for loose or damaged parts and then
stored in a clean, dry place in an upright position
to avoid
damage to the circuit breaker parts. A
coverµig
of paper will prevent dust from settling on
the circuit breaker parts and is preferred to packing
or other materials which are apt to absorb moisture.
FOR
SAFETY REASONS, STORE THE BREAKER IN
THE OPEN POSmON .
7
Courtesy of NationalSwitchgear.com

PART TWO
INSTALLATION
Type "DB" circuit breakers are furnished as
complete unit assemblies and the installation con-
sists
of: (1) bolting them to the supporting frame-
work
or structure; (2) connecting the current carry-
ing cables or bus bars; and (3) completing any
secondary control wiring that may be necessary.
Caution: During installation, the circuit
breaker should he in the open position. Be
sure to de-energize the load and control leads
to be connected, and also the section of the
switchboard where installation is being made.
Mounting dimensions and details of the front en-
closure cutouts
are shown in Figs. l, IA, IB, and IC.
To preve nt distortion of the breaker panel, the
supporting structure should be checked for align-
ment. Magnetic material
in the mounting structure
should have at least two inches clearance to the
breaker studs.
A
manual closing handle is supplied with each
order of DB-75 and DB-100 breakers. This handle
is for maintenance only and in no case should it be
used for closing the breaker when primary circuit
is energized.
8
CONNECTIONS
Typical circuit
breaker wiring diagrams are
shown in Fig. 2. The connecting cables or bus bars
should have adequate current carrying capacity,
or heat will be conducted to the circuit breaker
resulting in possible excessive temperature rise.
Connecting cables or bus bars must be supported
so that the circuit breaker studs will not be subjected
to unnecessary stresses.
ENCLOSURES
The
breaker is normally mountedin theenclosure
along with accompanying bus work terminating in
cable clamps. Where covers are mounted on en-
closures, they are tobe removed and drilledtoprovide
for connecting cable. All connections should be
clean, smooth and free from burrs to assume full
contact area. They should be firmly clamped or
bolted in place to prevent excessive heating. Cable
must be adequately braced to withstand full short
circuit
currents .
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Courtesy of NationalSwitchgear.com

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MOVABLE
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MANO TRIP AND PROVISION FOR PADLOCKING
BREAKER IN TRIPPED POSITION. PADLOCKS
FURNISHED
BY CUSTOMER
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INSTALLATION---------------------- ---- ------------ -- ---- --~·~ . B~ - =33~-850-=::;~4:&~5~
" DB" AIR CIRCUIT BREAKERS
s ue - 1
llOT ~C
~~x ~
FIG .7 X 7
BO '!' W' 4 TC
llUX .t
SW
0
r u.6 x 7
BOT ~G 4 :r e
AUX .t
SW b
Fl 9 X 1
FI G. 2. Typical Wiring Diagrams
13
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PART THREE
MAINTENANCE
POLE UNIT
Each pole unit (Fig. 3) is mounted on a separate
molded base. The molded bases are attached to the
mounting panel and provide insulation for the break-
er studs .
The upper stud and contact are attached to the
molded base by two bolts. The moving contact arm
is pivoted on the lower stud and is attached to the
cross bar through an insulating link. The lower stud
is fastened to the molded base by four bolts.
Contacts. (See Fig. 3.) The arcing contacts must
touch first on closing and open last on opening.
Do not adjust one set of contacts without check-
ing the complete sequence of all poles. With the
breaker open proceed in the following order:
1. Tum adjusting nuts (A) on insulating link to
vary main contact pressure. Use .005 feeler gauge,
1,4 inch wide by 6 inches long, inserted as shown
in Fig. 4A to check clearance.
Feeler (X) above contact fingers insures that they
have all been deflected. Feeler (Y) inserted below
fingers insures that they have not gone solid.
z. With breaker closed and latched, apply pres -
sure on each stationary arcing contact, part "a" of
Fig. 4B. When spring is fully compressed or solid,
clearance from moving arcing contact (b) should
be 'h2 to 1/
8
inch. Adjust by turning nuts (A) on
insulating link-however, clearances of main con-
tacts as described in part (1) must be maintained.
3. Check the above adjusbnents on all three
poles. After all poles have been adjusted and with
one set of arcing tips just touching, the clearance
between the other two sets of arcing contacts should
not exceed
1
/is inch.
Maintenance of Contacts. Rough or high
spots should be removed with a file or sandpaper.
When dressing contacts be sure to protect the
hinged contact of all poles with a cloth to prevent
foreign matter from lodging in the hinged contact.
Caution: All power must be removed when
replacing, maintaining or adjusting contacts.
OPERATING MECHANISM
The operating mechanism (Figs. 3-3A) is non-ad-
justable and consists of a series of non-ferrous links
designed to secure low closing and trippng forces.
To check for friction, with the breaker open, raise
trip finger and slowly lower the closing handle.
Release trip finger and slowly raise handle. The
linkage should follow the handle without sticking
and a "click" will be hea . rd just before the handle
reaches the full up position.
To remove the mecha .nism proceed as follows:
1. Remove the breaker cross bar.
2. Loosen the outboard bearings at the ends of
the trip bar.
a. In rea .ssembly, tighten bolts holding out-
board bearings only when bearings have been
adjusted to prevent any binding of trip shaft.
3. Remove ·the tension rods between the mech-
anism and aluminum panel.
4. Free the pin (J-3) *from the moving core. To
free the pin, first remove the cotter pin from the
spacer on the right side of the pin. Partially close
the breaker until the pin lines up with two holes in
the sides of the mechanism frame. Hold the moving
core up, and then drive the pin to the right just
far enough to clear the moving core rod. Lower the
moving core until it hits its stop. Drive the pin to
the left into its original position.
5. Remove the four mounting bolts.
•The first letter or number refers to the item and the eecond to the fiqure number. (Item J- Fiq. No. 3.)
14
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INSTALLATION------------ ----------------------------------~1~.B~-~3~=850-4::;;::.:&~s~
"DB" AIR CIRCUIT BREAKERS
MOVING CORE
AND PUSH ROD
4IO
ARC CHUTE
400
OVERCURRENT
TRIPPING DEVICE
414
/ MOVING ARCING
- ·1 CONTACT
HINGE FINGERS
_ __.,.- 423
"- -
. ::i I ' LOWER STUD
. L 424
- :-;-:- '-'l
m n'7r.--- ~· +. ~ _r J
HINGE. FINGER
SPRINGS
425
CLOSED TRIPPED
OPEN (RESET)
FIG. 3. Cross-Sectional View of Air Circuit Breaker
15
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N>ICATOR
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~I FACE - PLATE ,HANX.E,
a PANTOGRAPH LINK S
. NOT SHOWN
ESCUTCHEON
~OGRAPH LINKS
~CHANISM EXTENSION
TEST POSITION MARK
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I DISCONNECT POSITION MARK
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MAINTENANCE HANDLE
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MAINTENANCE~~~~~ ~~~~~~~~~~~~----~--~--~~l.~B~.3~~~850-;;.;,.~4~& ~5~
" DB" AIR CIRCUIT BREAKERS
FEELER GAGE "X"
(.005) ~
FEELER GAGE "V"
(.005)--
FIG. 4A FIG. 4B
FIG. 4. Adjusting Limits of Mai n an d Arcing Con ta cts
a. Caution: These bolts are also the
mounting bolts for the closing solenoid;
therefore, support the solenoid while remov-
ing the bolts .
6. Remove the mechanism.
7. Before assembling mechanism check sliding
surfaces of two latches shown
at "B", Fig. 3. These
surfaces must
be clean, free of burrs , and have not
more
than .035 inch clearance in the rese t position.
The mechanism
is factory lubricated for We.
CLOSING NOMINAL
BREAKER COIL
CONTROL CLOSING TRIPPING
TYPE BURDEN VOLTAGE AMPERES AMPERES
CLOSING SOLENOID
The closing solenoid (Fig. 5) is non-adjustable.
To rem
ove the cl ose co il, proceed as fo llows:
1. Caution: Remove the close coil circuit
v oltage .
Z. Disconnect the wires from the close coil ter-
minals.
3. Loosen the l oc king clip (4) on the bottom of
the moving core .
RECOMMENDED CLOSING
FUSE AMPERE RATING
250 VOLT 600 VOLT
FUSE
STYLE
NUMBER
Standard l
NEC
Time
Lag
Standard I
NEC
Time
Lat
DB-75 All 48DC
.. 5 .. .. .. .. .... ...... ..
125 DC 32 2 10 .. .. ..
120A823H04
250DC 18 1 6 .. .. .. 120A823H03
230AC 32 .5 10 .. .. .. 120A823H04
460AC 18 .2 .. .. 6 .. 120A824H03
575AC 15 .3
.. .. 6 .. 120A824H03
DB-100 A
ll 24DC .. 9.5 . . . . ..
..
. ...... .....
DBF-40
125DC 32 2 15 .. .. .. 120A823H05
250DC 18 1 10 .. .. .. 120A823H04
230AC 32
.5
15 .. .. .. 120A823H05
460AC
18 .2 .. .. 10
.. 120A824H04
575AC 15 .3 .. .. 10 .. 120A824H04
ll5AC .. l .. .. . . .. . ....... . .. .
Note: F or A-C closing use 3 KVA source or larqe r
17
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MAINTENANCE.------------------------------------------------
~
(
M OVING CO RC
ROD
!> O LLH OIO
LtG
nG. 5. Closing Solenoid Construction Detaila
4. Remove bolts (5), locking clip (4), and the
relay trip bracket (6).
5. Remove bolts (3), and using a rawhide or
plastic mallet remove the bottom stationary core (7).
&. Remove the coil.
7. After assembling coil and breaker, but before
connecting
the coil, check proper co-ordination
between
breaker closing and relay tripping. Ener-
gize relayoperating coil only (Fig.
11), and manual-
ly close
breaker very slowly. The relay contacts
should
trip free slightly before the position at which
the mechanism pawl (C3 ) drops in the latched
position.
OVERCUIUtENT TRIPPING DEVICE
Descriptioa. The overcurrent tripping device
(Fig. 6), for
the circuit breaker is an air delayed
magnetictypeof device . The time-currentcharacter-
istics of
the trip unit a. re as follows:
1. Long delay and short delay.
2. Long delay and instantaneous.
3. Instantaneous.
18
The various ratings of each general type are of
similar construction
and differ only in springs and
calibration.
The overcurrent tripping device
can be removed
from
the breaker easily and replaced with another
unit of
the same or different rating without affecting
the calibration of the units involved.
Constr11ctioa. The mounting frame casting sup-
ports
the two sub-assemblies of the trip unit. On the
upper part of the frame are the two magnetic
armatures and their associated links and brackets.
Fastened to
the lower part of the mounting frame is
the moldarta box which contains the calibration
springs, time delay elements
and calibration knobs.
This box is held to the mounting frame by two long
screws
at the bottom of the calibration box.
lmtallatioa aad Removal
Caatioa: Before removing or installing a
tripping device, be sure that the breaker is in
the open position and de-energized.
To remove an overcurrent tripping device from
the breaker, looeen the two bolts at the bottom
of the mounting frame (L-3) until they tum freely. )
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l'WIADlTENAN~E, ___________________________________________________ 1._B._U- __ aso- ...... ~4-&_s_
"D B" AIR CIRCUIT BREAKERS
Then loosen the two bolts at the top of the mounting
frame while supporting
the trip unit so that it
does
not fall. These two bolts clamp a slotted angle
mounting bracket and merely have to be loosened;
they
do not have to be removed from the mounting
frame. The trip unit is
then free to be removed
from the
breaker by lowering it down behind the
breaker platform.
To install a tripping device
on a breaker, first
make certain that
the breaker is open and is not
connected to live circuits.
Then loosen the upper
mounting bolts on the trip unit so that the bolts
can slide into the slotted mounting brackets on the
stationary yoke. Then install
the trip unit from the
bottom of the breaker, sliding it up behind the
mechanism platform. Start the bottom two mounting
bolts,
but do not tighten completely. Next, align the
trip unit so that the gaps between the tapered
portions of the main armature are app roximately
equal when the main armature is closed. Then
tighten all four mounting bolts securely.
INSTAllTANEOUS MOVING MAGNET- - -,
2!10
n
, -- - ~~ --
BREAKER TR IP FINGER---1._·-· '' ·-
252
LONG DELAY MOV I NG MAGNET
Ul
TRIP CRANK
2!14
TRIP SCREW
2S!I
SHAFT
258
LONG OlLAY TIMlllO
AllO RESET VALVE
2110
Adjastment of Trip Screw. The trip screw
mounted
on the trip fingermust be adjusted properly
to obtain
proper tripping.
Caution: Since this adjustment involves
tripping the breaker, care must be taken to
keep fingers and face away from all contact
arm .s and operating linkage.
To proceed with the adjustment, turn the long
time dialat
the bottom of the calibration box counter-
clockwise to
the stop so that the trip unit is set for
minimum time delay.
Then close the breaker and
carefully reach und er the mechanism with both
band s and push the lower armature fully closed
with
the thumbs. Hold it closed for at least the
minimum long delay time (20 to 40 seconds). H the
breaker trips, reset the screw at the end of the
tripping finger until the breaker just barely trips.
Before re-adjusting
the trip screw, make sure that
the breaker is in the open position. After finding
the position of the trip screw at which the breaker
INSTANTANEOUS STATIONARY MAGNET
262
t-- -- LONG DELAY STATIOllARY MAGNET
LONG DELAY TIME DIAL
267
263
no. 6. Crosa-Sectional View of Ov ercurrent Tripping Device with Long Delay and Instantaneous Elemente
19
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MAINTENANCE-------------------------------------------------------
just trips, turn the screw exactly one full tum in
the direction to trip the breaker sooner. Check to
make
sure that the breaker will trip when either
armature is closed if long and instantaneous type
tr
ip units are used, or when both armatures are
closed if long and short delay type trip units are
used. The short delay armature is for timing only.
Closing
it alone will not trip the breaker.
Operation
Standard Overcurrent Tripping Device
(Refer to Fig. 7A)
When a small overload current flows through the
breaker pole unit conductor (R), it causes the moving
LEGEND•
J-TRIP CRANK
armature (B) to be attracted toward the stationary
core (A). The motion of the armature is retarded by
the diaphragm (D) whose motion is in tum 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 (J) far enough to trip the breaker by
moving
the trip lever (K). During this type of
tripping,
the tension spring (C) is not stressed
beyond its normal length.
On larger overload currents, the action is essen-
tially
the same as above except that the moving
armature (B) will close completely as soon as the
overload is applied. When the armature closes, tl:e
A-LONG DELAY STATIONARY MAGNET
B-LONG DELAY MOVING MAGNET K·BREAKER
TRIP FINGER *
GUIDE BEARING
_j_ SOLID JOINT
C-
LONG DELAY FORCE LIM ITING SPRING
O-DIAPHRAGM
E-A IR CHAMBER
F·LONG DELAY VALVE
ANO DIAL
G-LONG DELAY PICK-UP CALIBRATION SPRING
H-RESET VALVE
I I
L·INSTANTANEOUS STATIONARY MAGNET
M-INSTANTANEOUS MOVING MAGNET
Q-INSTANTANEOUS PICK-UP CALIBRATI
ON SPRING
R·BREAKER MOVING CONTACT ARM
W·SHAFT
--~-LONG DELAY PICK·UP ADJUSTMENT
RESE TT ABLE
DE L AY
l""----T--LONG DELAY TIME
ADJUSTMENT
+PINNEO JOINT
I ,
-1 - NO .JOINT
,,!.. STOP SURFACE
ADJUSTABLE
SCHEMATIC DI AGRAM
20
CURRENT MA GN ITUDE
FIGURE 7A
TYPICAL TRIPPI NG CHARACTERISTICS
FIGURE 78
FIG. 7. Schematic and Typical Time-Current Characteristics of Overcurrent Tripping Device with Long
Delay and Instantaneous Elements
-; )
. - ~ >
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