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Page 18
A second more convenient indicator is located on the
front of the circuit breaker (Figure 3-4). Small viewing
windows located on the front lower portion of the circuit
breaker truck provide a green and red "Go" or "No Go"
flag indication of each vacuum interrupter's contact ero-
sion condition. This indicator is provided as a conve-
nient reference when the circuit breaker is installed in its
cubicle. As long as the line in the window is in the green
portion of the indicator, the contacts are satisfactory.
When the line reaches the red portion of the indicator,
the interrupter assembly must be replaced.
5-2.3 LOADING SPRING INDICATION
The contact loading spring indicator is an additional
method provided to indicate conditions within the vacuum
interrupter, as well as the overall system condition. The vis-
ible indication, on each phase, is used to indicate whether
the contact loading springs are maintaining the proper con-
tact pressure to keep the contacts closed. Severe contact
erosion or an adjustment need after an interrupter assem-
bly replacement would result in an unacceptable indication
from this indicator (Figures 6-4 and 6-5).
5-2.4 CONTACT WIPE AND STROKE
Contact wipe is the indication of (1) the force holding the
vacuum interrupter contacts closed and (2) the energy
available to hammer the contacts open with sufficient
speed for interruption.
Stroke is the gap between fixed and moving contacts of
a vacuum interrupter with the circuit breaker open.
The circuit breaker mechanism provides a fixed amount
of motion to the operating rods. The first portion of the
motion is used to close the contacts (i.e. stroke) and the
remainder is used to further compress the preloaded
wipe spring. This additional compression is called wipe.
Wipe and Stroke are thus related to each other. As the
stroke increases due to the erosion of contacts, the wipe
decreases. A great deal of effort has been spent in the
design of all Cutler-Hammer vacuum circuit breakers, in
order to eliminate the need for field adjustments of wipe
or stroke.
!
THERE IS NO PROVISION FOR IN SERVICE
ADJUSTMENTS OF CONTACT WIPE AND STROKE.
ALL SUCH ADJUSTMENTS ARE FACTORY SET
AND SHOULD NOT BE ATTEMPTED IN THE FIELD.
CAUTION
5-3 STORED ENERGY MECHANISM
!
KEEP HANDS AND FINGERS AWAY FROM THE CIR-
CUIT BREAKER'S INTERNAL PARTS WHILE THE
CIRCUIT BREAKER CONTACTS ARE CLOSED OR
THE CLOSING SPRINGS ARE CHARGED. THE CIR-
CUIT BREAKER CONTACTS MAY OPEN OR THE
CLOSING SPRINGS DISCHARGE CAUSING A
CRUSHING INJURY. DISCHARGE THE SPRINGS
AND OPEN THE CIRCUIT BREAKERS BEFORE PER-
FORMING ANY CIRCUIT BREAKER MAINTENANCE,
INSPECTION OR REPAIR.
The spring stored energy operating mechanism is
arranged vertically in front of all VCP-W circuit breakers
(Figure 3-5). It includes all the elements for storing the
energy, closing and tripping of the circuit breaker, as
well as manual and electrical controls. The manual con-
trols are all front accessible. Motion to close and open
the interrupter contacts is provided through operating
rods connecting the mechanism pole shaft to the bell
cranks of the interrupter assemblies.
5-3.1 OPERATION OF STORED ENERGY
MECHANISM
The mechanism stores the closing energy by charging
the closing springs. The mechanism may rest in any one
of the four positions shown in Figure 5-4 and as follows:
a. Circuit breaker open, closing springs discharged
b. Circuit breaker open, closing springs charged
c. Circuit breaker closed, closing springs discharged
d. Circuit breaker closed, closing springs charged
5-3.2 CHARGING
Figure 5-5 is a schematic view of the spring charging
parts of the stored energy mechanism.
The major component of the mechanism is a cam shaft
assembly which consists of a drive shaft to which are
attached two closing spring cranks (one on each end),
the closing cam, drive plates, and a free-wheeling ratch-
et wheel. The ratchet wheel is actuated by an oscillating
mechanism driven by the motor eccentric. As the ratchet
wheel rotates, it pushes the drive plates which in turn
rotate the closing spring cranks and the closing cam
with it.
I.B. 3A74792H04
WARNING
Effective 7/97
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