Page 68
1.8. 33-790-11
Section 9 - DSL Circuit Breakers and Fuse Trucks
9.0 GENERAL
DSL circuit breakers are coordinated combinations
of
standard DS circuit breakers and integrally mounted
series connected current limiters. They are available
in
two frame sizes, DSL-206 and DSL-416. The primary
purpose
of
the current limiters is to extend the interrupt-
ing rating
of
the DS circuit breaker up to 200,000
amperes RMS symmetrical current.
If
the current limiters
are sized per Table
5,
the circuit breaker will function and
interrupt the routine fault currents. Infrequent high faults
will be cleared by the limiter. The limiters protect the cir-
cuit breaker on faults above the rating
of
the breaker. The
limiters will blow below the circuit breaker short-time rat-
ing if the fault currents equal the system maximum
capacity.
In
some applications the current limiters will be sized
smaller than necessary for protection
of
the DSL circuit
breaker
in
order to provide protection for downstream
equipment. When this is done, the current limiters will
blow on fault currents which could have been satisfacto-
rily interrupted by the basic circuit breaker.
Type DS-3200 and DS-4000 fuse trucks provide for sep-
arate mounting
of
Class L current limiting fuses
on
dra-
wout trucks for use
in
series with DS-632 and DS-840
circuit breakers respectively. This separate mounting is
made necessary by the size
of
the Class L fuses and
their high temperature characteristics.
9.1
DSL CURRENT LIMITERS
Available current limiter ratings and their recommended
applications are listed
in
Table
5.
Do not replace limiters
with sizes other than permitted by the table. Cutler-Ham-
mer DSL current limiters have been tested and approved
by
Underwriters Laboratories, Inc. for use
in
DSL circuit
breakers when applied according to Table
5.
They are
not electrically
or
physically interchangeable with current
limiting fuses
of
any other design.
The current limiters are held
in
place
in
an extension pro-
vided on the back
of
the circuit breaker. This extension
makes the DSL circuit breakers eight inches deeper than
the corresponding
DS
circuit breakers. See Figures 77,
78 and 79. The current limiters can only be removed from
the circuit breaker and replaced when the circuit breaker
is removed from its associated compartment. For this
reason there is no fixed mounted version
of
the DSL cir-
cuit breakers.
Table 5 - Sensor and Limiter Ratings
Breaker
Sensor
e Recommended
Limiter
Ratings
**Maximum
Type Rating
*Minimum
DSL-206 800A 1600A 1200A 2000A
DSL-206 600A 1200A
BODA
2000A
DSL-206
Less than 1200A 125% or more of 2000A
600A
sensor rating
DSL-416 1600A 3000A 3000A 3000A
DSL-416 1200A 2500A 2000A 3000A
DSL-416
Less than 2000A 125% or more of
3000A
1200A
sensor rating
t!J
Minimum nuisance blowing
of
limiters
* Use only when current limiting is required for downstream equipment. If long
delay
pick-up is set above 100%, minimum limiter ratings should not be used.
** Highest rating that will protect breaker.
Fig. 77 DSL-206 Breaker Side View (388138)
9.2 BLOWN LIMITER INDICATOR
The Blown Limiter Indicator provides a visual indication
on the front
of
DSL circuit breakers when a current limiter
in
any phase has interrupted a short circuit. It also
insures that the circuit breaker will be tripped when any
current limiter has blown, to prevent single phase power
being applied to a three-phase load. See Figure 80.
This device consists
of
three solenoids, each connected
in
parallel with one
of
the limiters. When a limiter is
blown, the resulting voltage across the open limiter
causes the associated solenoid to operate, tripping the
circuit breaker mechanically and extending
an
indicator
through the front cover
of
the circuit breaker. See Figure
78.
The indicator will remain extended and the breaker
will be held trip-free until the reset button is pushed. If the
device is reset and the breaker reclosed
on
an energized
Effective October 1998
Courtesy of NationalSwitchgear.com
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