Eaton VCP-W, Инструкции по установке, эксплуатации и техническому обслуживанию, Страница: 35 / 81

IB131006EN
Page 29
Effective 07/2017
SECTION 5: DESCRIPTION AND
OPERATION
5-1 INTRODUCTION
Type VCP-W, VCPW-SE and VCPW-ND vacuum circuit
breakers are horizontal drawout designs for use in metal-
clad switchgear compartments. Most ratings can be
stacked two high in a vertical section resulting in a
considerable savings of floor space.
Vacuum interrupters are used with all circuit breakers to
close and open the primary circuit. All VCP-W circuit
breakers are operated by a front mounted spring type
stored energy mechanism (Figure
3-3 ) . The stored
energy mechanism is normally charged by an electric
motor, but can be charged manually with the manual
maintenance tool. Since the same basic, front accessible
mechanism is used for all VCP-W circuit breakers, a
minimum investment in spare parts is required.
The primary insulation used with Type VCP-W circuit
breakers is flame retardant and track resistant glass
polyester except for the Type VCPW-SE circuit breaker.
The VCPW-SE special environment circuit breaker
design utilizes cycloaliphatic epoxy for its primary
insulation. “Fast On” type secondary control terminations
are used on Types VCP-W and VCPW-ND circuit
breakers, while the Type VCPW-SE circuit breaker
utilizes ring type secondary control terminations.
The rest of this section describes the overall operation of
the VCP-W circuit breaker as well as the function and
operation of all major sub-assemblies and/or parts. Keep
in mind that VCP-W will be used throughout the text
when referring to any one of the three types of circuit
breakers, unless there is a specific difference between
VCP-W, VCPW-SE and VCPW-ND.
5-2 INTERRUPTER ASSEMBLY
Vacuum interrupters are mounted vertically and
supported from the fixed stem which is clamped to the
top conductor. The exclusive current transfer system
consists of a series of plated, high-conductivity copper
leaf conductors that are pressed on the movable
interrupter stem. This design provides a multipoint contact
resulting in low electrical and thermal resistance. Utilizing
this non-sliding current transfer system between the
movable stem and the breaker main conductor
eliminates the need for maintenance (Figure
5-1 ) .
Multiple finger, floating type primary disconnecting
contacts at the ends of the top and bottom conductors
provide a means for interfacing with the primary
conductors mounted in the switchgear (Figure
3-4 ) .
Figure 5-1 Typical VCP-W Rear View Showing Vacuum
Interrupters and Current Carrying System
Direct acting insulated operating rods in conjunction with
the circuit breaker’s mechanism provide a fixed amount of
interrupter movable stem motion. This motion is directly
related to the interrupter’s “Wipe” and “Stroke,” each of
which is discussed in detail later in this section.
5-2.1 VACUUM INTERRUPTER
Type VCP-W Vacuum Circuit Breakers utilize vacuum
interrupters for interruption and switching functions. The
vacuum interrupters use petal type copper chrome
contacts for superior dielectric strength, better
performance characteristics, and lower chop current.
Vacuum interruption provides 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 (Figure
5-2 ) . In the
closed position, current flows through the interrupter.
When the contacts are opened, the arc is drawn between
the contact surfaces. It is moved rapidly around the
slotted contact surfaces by a self-induced magnetic force,
which prevents gross contact erosion as well as the
formation of hot spots on contact surfaces. The arc burns
in an ionized metal vapor which continually leaves the con-
tact area and condenses the surrounding metal shield.
Courtesy of NationalSwitchgear.com