Description And Operation; Circuit Breaker Elements; Interrupter Assembly; 5-2.1 Vacuum Interrupter - Eaton Cutler-Hammer VCP-WR 18 Series Instructions For The Use, Operation And Maintenance

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SECTION 5: DESCRIPTION AND
OPERATION
Cutler-Hammer Type VCP-WR breaker elements are
vacuum type interrupting elements designed to offer
value added construction. The VCP-WR Red Line family
of circuit breaker elements is comprised of three ele-
ment types (Series 18, Series 20 and Series 29). The
nominal widths are 18 inches for Series 18, 20 inches
for Series 20 and 29 inches for Series 29 (Figures 3-1,
3-3 and 3-5). Any one of the three available elements
can be used as a retrofitting drawout breaker when oth-
ers provide and combine the appropriate cell interface,
truck, levering mechanism, secondary connections,
interlocks and other accessory items with the VCP-WR
element. VCP-WR elements can also be used for fixed
breaker applications with the customer responsible for
all required interfaces and interphase barriers. The
appropriately sized interphase barriers must be installed
to comply with individual rating electrical clearance
requirements as described in Section 6. A movable
truck and levering mechanism would not be required for
a fixed breaker application. Details concerning mechani-
cal and electrical interfacing needs associated with the
use of a VCP-WR breaker element are found in Section
6 of this instruction book.

5-1 CIRCUIT BREAKER ELEMENTS

Series 18, 20 and 29 VCP-WR circuit breaker elements
are designed and tested for use and installation in keep-
ing with ANSI Standard C37.59. The three circuit break-
er element designs can be used for drawout or fixed
applications depending upon how others use and/or
retrofit the VCP-WR breaker elements. All safety inter-
locks required by ANSI Standards are part of the break-
er element and are integral to all three designs. Certain
required interlocks, however, are only complete when
compatible cell interlock devices are provided. The
matching cell interlocks, whether mechanical or electri-
cal, are the total responsibility of the customer.
Interfacing information is provided in this instruction
manual to simplify the interfacing task.
The highly reliable mechanisms for all three designs are
similar front, vertically mounted spring stored energy
types. The designs not only aid with personal safety, but
also provide for simplified inspections and servicing
accessibility (Figure 5-1).
Circuit breaker duty vacuum interrupters are used to
close and open primary circuits. The vacuum interrupters
used have a proven record for reliability, long life and
minimal maintenance (Figures 3-2, 3-4 and 3-6).
The standard primary insulation used on all VCP-WR
breaker elements is high strength, flame retardant glass
polyester. Cycloaliphatic epoxy primary insulation is an
available option with the Series 29 VCP-WR breaker
element. Type SIS AWG #14 wire is used on all VCP-
WR control circuits.

5-2 INTERRUPTER ASSEMBLY

Vacuum interrupters are mounted vertically and support-
ed from the fixed stem fastened to the top or bottom
conductor, depending upon which VCP-WR breaker
series. The Series 20 VCP-WR breaker element clamps
the fixed stems to the bottom conductors (Figure 5-2).
The Series 18 and 29 breaker elements clamp the fixed
stems to the top conductors (Figures 5-3 and 5-4). All
configurations, however, utilize a patented V-flex non-
sliding current transfer system. The current transfer sys-
tem consists of a series of tin-plated, high-conductivity
copper leaf conductors that are swaged onto the mov-
able interrupter stem. This provides a multi-point contact
resulting in low electrical and thermal resistance. Since
the current transfer from the movable stem to the circuit
breaker conductor is a non-sliding design, no mainte-
nance is required.

5-2.1 VACUUM INTERRUPTER

Type VCP-WR breaker elements utilize vacuum inter-
rupters for interruption and switching functions (Figure
5-5). Vacuum interruption offers the advantages of
enclosed interrupters, reduced size and weight, short
interrupting time, long life, reduced maintenance, and
environmental compatibility.
Arc interruption is simple and fast. In the closed posi-
tion, current flows through the interrupter. An arc is
drawn between the contact surfaces when the contacts
are opened. It is rapidly moved around the slotted con-
tact surfaces by a self-induced magnetic force which
prevents gross contact erosion as well as the formation
of contact surface hot spots. The arc burns in an ionized
metal vapor which continually leaves the contact area
and condenses on the surrounding metal shield. At cur-
rent zero the arc is extinguished and vapor production
ceases. Very rapid dispersion, cooling, recombination,
and deionization of the metal vapor plasma together
with fast condensation of metal vapor products cause
the vacuum to be quickly restored. Hence, the opened
contacts withstand the transient recovery voltage.
I.B. 8295A61H03
Effective 7/97