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I.B. 3A74499B
Page 16
Effective 11/97
SECTION 5: DESCRIPTION AND
OPERATION
Cutler-Hammer Type W-VAC breakers are horizontal
drawout vacuum circuit breakers. They are designed
specifically to IEC 56 and KEMA certified to IEC
Standards, including their earthing system.
Type W-VAC breakers are available in three mounting
configurations. These include single tier designs and
double tier designs for use in medal-clad switchgear,
and a basic element design for use in retrofitting. For
the single tier design, the basic breaker element is
mounted on a carriage assembly. The basic breaker
element is mounted on a cradle assembly for the dou-
ble-tier design. The carriage assembly and the cradle
assembly both incorporate the racking mechanism and
required safety interlocks.
The basic breaker element, the breaker element with a
carriage assembly, and the breaker element with a cra-
dle assembly are designed to accept a variety of face-
plates or covers. This permits the breakers to be very
flexible with respect to the type of structure used to form
the final switchgear assembly.
Possibility 1 : The basic breaker element, by itself, is
used for retrofitting purposes (Figures 3-3 and 3-4).
Possibility 2: The basic breaker element combined with
a carriage assembly is used for single tier switchgear.
The breaker and carriage combination, however, can be
utilized in a flush mounted configuration (Figure 5-1) or
a behind the door configuration. The flush mounted
design cover forms a deadfront design with the struc-
ture, once the breaker is racked into the fully connected
position.
Possibility 3 :The basic breaker element combined with
a cradle assembly is used for double tier switchgear.
This combination is only for use in a behind the door
configuration (Figure 5-2).
W-VAC breakers utilize Westinghouse vacuum inter-
rupters to close and open the primary circuit. The mech-
anism is a front mounted, spring stored energy type,
which is common to all ratings. This one front mounted
mechanism is easy to inspect, accessible for servicing
and requires a minimum of spare parts. Because of the
inherent long life characteristics of the vacuum inter-
rupters and the highly reliable spring stored energy
mechanism, W-VAC circuit breakers provide long trou-
ble free service with a minimum of maintenance.
The primary insulation used throughout the W-VAC
design is flame retardant and track resistant glass poly-
ester.
5-1 INTERRUPTER ASSEMBLY
Vacuum interrupters are mounted vertically and support-
ed from the fixed stem clamped to the top conductor
(Figure 5-3). The current transfer system consists of a
series of tin-plated, high-conductivity copper leaf con-
ductors that are pressed onto the movable interrupter
stem.This provides a multipoint contact resulting in low
electrical and thermal resistance. Since the current
transfer from the movable stem to the breaker main con-
ductor is a non-sliding design, no maintenance is
required.
5-1.1 VACUUM INTERRUPTER
Type W-VAC breakers utilize vacuum interrupters for
interruption and switching functions. Vacuum interrup-
tion offers the advantages of enclosed interrupters,
reduced size and weight, short interrupting time, long
life, reduced maintenance, and environmental compati-
bility.
Figure 5-1 Flush mounted configuration.
Summary of Contents for 36W-VAC25
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