GE Industrial Solutions PowerVac PV-VL 13.8-1000-0 and -1 - Manual (Page 28)

Page 28 GEH 6468A - Power/Vac VL Breaker
stored energy mechanism without closing the
breaker.
8. OPERATION
The PowerVac
®
VL vacuum circuit breaker uses a
sealed vacuum power interrupter to establish and
interrupt a primary circuit. Primary connections to
the associated metal-clad switchgear are made by
pole assemblies, electrically and mechanically
connected to the vacuum interrupters. Molded
supports, one per pole on a three pole breaker,
provide interchangeable mountings for the primary
poles, interrupters, and heat dissipation fins (where
used). The operating mechanism provides
horizontal motion at each pole location in order to
move the lower contact of the vacuum interrupters
from an open position to a spring-loaded closed
position and then back to the open position on
command.
The ML-18VL mechanism (Figs. 17 & 23) is the
stored-energy type and uses a gear motor to
charge a closing spring. During a closing operation,
the energy stored in the closing spring is used to
close the vacuum interrupter contacts, charge the
wipe springs which load the contacts, charge the
opening springs, and overcome bearing and other
frictional forces. The energy then stored in the wipe
and opening springs will open the contacts during
an opening operation.
Closing and opening operations are controlled
electrically by the control switch on the metal-clad
door or remote relaying. Mechanical control is
provided by manual close and trip buttons on the
circuit breaker.
The closing spring may be manually charged, and
a method for slow closing the primary contacts is
available when the circuit breaker is withdrawn
from the metal-clad cubicle. (See Section 10) The
mechanism will operate at the ac or dc voltage
indicated on the circuit breaker nameplate.
8.1. CLOSE SPRING CHARGING
Figure 23 shows a front view of the ML-18VL in a
schematic form. The primary contacts are open
and the closing spring is charged. The closing
spring charging system consists of a closing spring
(1, view B) mounted on the left side of the breaker
and the electrical charging system mounted on the
right side of
the breaker. Both components are
fastened
to the cam shaft (2, view B). A manual charging
system (3, view A) is provided so that the
mechanism can be slow closed and the closing
spring can be charged if there is a loss of electrical
control power.
Spring charging is accomplished electrically by a
rotating eccentric on the output shaft of a gear
motor driving pivoted charging arms (4, view C).
The charging arms oscillate about the centerline of
a ratchet wheel (5, view C). A driving pawl (6, view
C), mounted within the charging arms, oscillates
with the charging arms. Starting from its rear-most
position, the charging arms rotate forward, while
spring forces engage the driving pawl with a tooth
on the ratchet wheel. The ratchet wheel is
advanced by the rotating charging arms and pawl
assembly. Advancement of one tooth spacing is
provided for each oscillation of the system. The
ratchet motion is restricted to one direction by a
spring-loaded holding pawl that prevents the
ratchet wheel from going backwards as the
charging arms oscillate back to pick up the next
tooth. Thirteen complete cycles of the charging
arms are needed for a full charge of the closing
spring.
The efficient, compact gear motor accomplishes
this action in about two seconds. When the
charging cycle is complete, the ratchet wheel is
positioned so that a missing tooth is adjacent to the
driving pawl and any motor overspin will not drive
the ratchet wheel, thus preventing damage to the
system.
When the spring is completely charged, the
assembly is retained in that position by the close
latch until it is desired to close the circuit breaker.
The closing coil cannot be electrically energized
unless the closing spring is completely charged.
This action is prevented by the 52/CHG switch in
the closing circuit.
The manual charging system (3, view A) works
directly on the cam shaft where a one-way clutch
(7, view A), driven by a manual handle, provides
rotation of the ratchet wheel. Manual pumping of
the handle advances the ratchet wheel and the
holding pawl prevents counter-rotation while the
handle is returning for another stroke. Approxi-
mately eight complete strokes of the manual
handle are required for one complete spring-
charging operation. When the spring charge
indicator (8, Fig. 17) shows "CHARGED", MANUAL
CHARGING MUST BE DISCONTINUED TO
AVOID MECH-ANISM DAMAGE.