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Instructional Book IB694C694-03
The 800 through 2000 amp frame DSLII Circuit Breakers
have the limiters integrally mounted on the drawout breaker
elements. On 3,200 and 4,000 amp frame combinations,
the limiters are mounted on separate drawout trucks. They
fit into compartments of equal size to their compatible
circuit breakers and are normally positioned adjacent to one
another.
On overloads and faults within the circuit breaker interrupt-
ing rating, the circuit breaker protects the limiters. On higher
fault currents exceeding the circuit breaker rating, the limit-
ers protect the circuit breaker.
Interlock arrangements trip the circuit breaker whenever any
limiter blows. The circuit breaker cannot be reclosed on a
live source unless there are three unblown limiters on the
circuit. The blown indicator provides a visual indication when
a current limiter in any phase has interrupted a short circuit.
In addition, it is the device that insures a circuit breaker will
be tripped when any current limiter has blown, preventing
single phasing.
DSLII-308 through DSLII-620 Circuit Breakers must be
completely withdrawn from the compartment, thus assuring
complete isolation, before the integral fuses are accessible.
Fuses for Types DSLII-632 and DSLII-840 Circuit Breakers
are mounted on a separate fuse truck. The fuse truck is key
interlocked with the circuit breaker to prevent withdrawing
or insertion unless the circuit breaker is disconnected.
NOTICE
REFER TO SECTION 4 FOR ADDITIONAL INFORMATION CONCERN-
ING LIMITER RATINGS, LIMITER REPLACEMENT, BLOWN FUSE
INDICATOR OPERATION, AND FUSE TRUCk INSTALLATION.
WARNING
THE CIRCUIT BREAkER'S FACEPLATE, INTERPHASE BARRIERS
AND ARC CHUTES MUST BE IN PLACE BEFORE INSTALLING A
CIRCUIT BREAkER IN A CIRCUIT BREAkER COMPARTMENT. IF
A CIRCUIT BREAkER IS ENERGIZED WITHOUT THESE ITEMS
PROPERLY INSTALLED, A DISASTROUS SHORT CIRCUIT FAULT
WITHIN THE SYSTEM COULD OCCUR, RESULTING IN EQUIPMENT
DAMAGE, BODILY INJURY AND/OR DEATH.
3-3 Basic Breaker Assembly
The basic breaker assembly includes a chassis, a con-
trol panel, an operating mechanism, a tripping system, a
levering-in device (drawout breakers only), various required
interlocks, and three insulated pole unit assemblies.
The control items needed for proper operation of the breaker
are located on the front panel. Controls are functionally
grouped for convenience. All operating personnel should be
familiar with their locations and functions (Figure 3-3).
Access to the operating mechanism and internally mounted
auxiliary devices is gained by removing the breaker face-
plate. The faceplate is held in place by front accessible bolts.
3-4 Pole Units
The pole unit assembly is a molded base of high strength
insulating material in which is mounted one to three sets of
primary contact assemblies. The exact design configuration
depends upon the frame size of the circuit breaker.
A DSII-308 pole unit assembly consists of a single molded
base and three sets of primary contact assemblies. The pri-
mary contact assembly is made up of two parts, the station-
ary contact assembly and the movable contact assembly,
each mounted individually in the insulating base (Figures 3-4
and 3-5).
Pole unit assemblies for other DSII circuit breaker frame
sizes are similar to the DSII-308 in design configuration,
except each of the three poles are mounted on individual
insulating bases (Figures 3-6 and 3-7).
3-4.1 Primary Moving Contact Assembly
The primary moving contact assembly for all ratings consists
of moving arms hinged at the bottom to the lower main
terminal through controlled pressure rotating contacts. At
the upper end of the primary moving assembly are the main
and arcing contacts. The arcing contacts of all frame sizes
are essentially the same design. The number of moving
arms, the number of main contacts, and the number of main
disconnect contact fingers vary with the frame size. A strong
and rigid insulating link operates the moving contact blade
assembly.
eaton corporation www.eaton.com
Effective July 2010
17
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