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Equipment Description
PowlVac® ARG & ARM Series 4 Vacuum Circuit Breakers
5kV & 15kV - 1200A, 2000A, & 3000A - 25kA, 36kA, 50kA, & 63kA
01.4IB.60306
The close latch, when released either by the
closing coil or the manual close operator,
allows the main closing spring to pull the
crank arms upward thus rotating the main
closing cam and driving the fundamental
linkage into the closed position. This
causes the main linkage to rotate the
jackshaft such that the operating pushrods
(
) are driven toward the
current carrying side of the circuit breaker.
Each operating pushrod assembly has a
recess at each end which encloses a contact
loading spring (
). At the end
of this spring is a spring yoke (
), which connects with bell cranks. The
spring yoke is restrained by a lock nut on
a stud which passes through the contact
loading spring and is attached to the
operating pushrod assembly. The contact
loading spring has initial compression such
that as soon as the vacuum interrupter
contacts touch, the springs are preloaded
to a value sufficient to resist vacuum
interrupter contact separation under the
highest electromagnetic forces exerted
by the rated short circuit current. Further
movement of the operating pushrod
assembly compresses the contact loading
spring even more and produces a gap
between the face of the spring yoke
and the lock nut. This “nut gap” is used
to evaluate the erosion of the vacuum
interrupter contacts.
For each phase, bell cranks (
are located on the outside of the lower
primary disconnecting devices
(
) and are supported by bearings.
Each bell crank is connected to an
operating pin, which passes through a slot
in the lower primary disconnecting devices
and engage an extension to the vacuum
interrupter assembly thus moving the
vacuum interrupter contact. The bell cranks
give an approximate 3 to 1 multiplication
of the contact loading spring force,
enabling a lower spring rate to be used.
It also multiplies the contact movement
by a factor of approximately 3, so that the
mechanism linkages have relatively large
movements and are less critical.
In the cam and fundamental linkage
positions (
), the contact loading
springs and the main opening springs are
both acting to compress the three (3) main
mechanism links. The jackshaft extends
from the left to the right side of the circuit
breaker frame and is supported at the
main circuit breaker frame side sheets and
by the mechanism side sheets. The outer
operating levers on the jackshaft have
connections to the circuit breaker opening
springs (
).
The fundamental linkage is restrained from
movement by the secondary trip prop
acting on the primary trip prop roller. A
component of force tends to make the
primary trip prop rotate upward, but it
is restrained by the secondary trip prop
face acting on the primary trip prop roller.
The clearance between the primary trip
prop roller and the secondary trip prop
is controlled by the primary trip prop
adjusting screw. When the trip shaft is
rotated by the action of the manual trip
operator or the primary shunt trip coil, the
secondary trip prop face moves downward
and permits the primary trip prop to rotate
upward, thus permitting the main linkage
to move upward and the jackshaft to
rotate, opening the circuit breaker. The left
jackshaft levers engage a shock absorber
), which controls the rebound
of the vacuum interrupter contacts on an
opening operation. An extension of the
jackshaft projects through the left circuit
breaker side sheet and operates the MOC
actuator (
).
