Magnum
1812.900A
11
2.6 Adapting
cassette
Drawout circuit breaker cassettes are built and shipped in
a “basic” configuration that can be adapted in the field to
mate with specific circuit breakers. Specifically, the
rejection interlock must be configured to the specific
circuit breaker to be mated with the cassette, and the
automatic secondary connections may have to be
installed or upgraded. These operations are described in
the following sections.
2.6.1
Rejection interlocks
Within any one physical frame size Magnum drawout
circuit breakers come in a variety of continuous current
and interruption ratings, some of which are incompatible
with others. Double wide circuit breakers also come with
several phase sequence options which are also
incompatible. To prevent the insertion of circuit breakers
with (1) inadequate interrupting capability, (2) with
physically incompatible primary disconnects or (3) with an
incompatible phase sequence, rejection interlock key
plates are provided on both the circuit breaker and
cassette. The key plate on the circuit breaker is pre-
assembled at the factory; but the cassette-side rejection
plate and key pattern must be assembled and installed by
the switchboard builder.
Figure 2-2: Rear View Showing Current Sensor Rating
Through Viewing Window
CAUTION
DO NOT DISABLE REJECTION INTERLOCKS.
DOING SO AND USING A LOWER CAPACITY
CIRCUIT BREAKER IN AN INCOMPATIBLE
CASSETTE COULD RESULT IN AN ELECTRICAL
FAULT WHICH COULD RESULT IN DEATH, BODILY
INJURY AND/OR EQUIPMENT DAMAGE.
The rejection interlocks are steel pins in the floor of the
circuit breaker cassette. As the circuit breaker is pushed
into the structure, the mating pins on the bottom of the
circuit breaker move past a set of corresponding pins in
the cassette, if the circuit breaker and cassette are
compatible. If the circuit breaker and the cassette are
mismatched, the rejection pins will block the insertion of
the circuit breaker into the cassette before the levering-in
mechanism is engaged.
Before attempting to push the circuit breaker into the
DISCONNECT position, compare the positioning of
rejection interlock pins in the cassette with Table 2-2 and
Figure 2-4 and the information supplied on the circuit
breaker’s nameplate. Proceed if the circuit breaker and
cassette are compatible.
Figure 2-3: One Side of Drawout Circuit Breaker Properly
Seated on Extension Rail
1. Molded Rail Supports
2. Extension Rail Cutout
1
2
