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Instructions for VR-Series
Replacement Breakers for
Westinghouse Type B20B/B22B
I.B. 94A1994R01
Page 17
Effective: April 2005
IB01301018E
WARNING
WARNING
FAILURE TO REPLACE THE INTERRUPTER ASSEMBLY WHEN
INDICATED BY THE CONTACT EROSION INDICATOR COULD
CAUSE THE BREAKER TO FAIL, LEADING TO DEATH, PERSONAL
INJURY OR PROPERTY DAMAGE.
5.1.3 CONTACT WIPE AND STROKE
Wipe is a measure of (1) force to hold vacuum interrupter contacts
closed and (2) energy to hammer the contacts open with sufficient
speed for safe and clean interruption.
Stroke is the gap between fixed and moving contacts of vacuum
interrupter with the breaker open.
The circuit breaker mechanism provides a fixed amount of motion to
the operating rods. 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 erosion of contacts, the wipe decreases. A great
deal of effort and ingenuity has been spent in the design of VR-
Series breakers, in order to eliminate any need for field adjustment
of wipe or stroke. Thus, there is no provision for adjustments.
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.
5.2 PHASE BARRIERS
Phase barriers are flat sheets of insulation placed between the
interrupter assemblies and on the sides of the breaker frame. All
four barriers are attached to the element through angle brackets
and lateral spacing is maintained by components of the breaker
element and frame. NOTE: To remove the outer phase barriers, the
ground plate and shutter roller must be removed. When placing the
ground plate back on the breaker, ensure that the rear edge is
parrallel with the truck frame. (Figure 5-3)
ALL FOUR PHASE BARRIERS MUST BE IN PLACE BEFORE
PLACING THE CIRCUIT BREAKER INTO SERVICE. FAILURE TO
HAVE THEM IN POSITION CAN CAUSE DEATH, SERIOUS
PERSONNEL INJURY AND/OR PROPERTY DAMAGE.
5.3 BUSHINGS AND DISCONNECTING CONTACT ASSEMBLIES
The line and load bushing assemblies, which are the primary circuit
terminals of the circuit breaker, consist of six silver plated conduc-
tors. Multiple finger type primary disconnecting contacts at the
ends of the conductors provide means for connecting and
disconnecting the breaker to the bus terminals in the switchgear
compartment.
5.4 STORED ENERGY MECHANISM
The spring-type stored energy operating mechanism is mounted on
the breaker frame and in the front of the breaker. Manual closing
and opening controls are at the front panel (Figure 3-3) so that they
are accessible while the breaker is in any of its four basic positions.
(See Section 4.2)
The mechanism stores the closing energy by charging the closing
springs. When released, the stored energy closes the breaker,
charges the wipe and resets the opening springs. The mechanism
may rest in any one of the four positions shown in Figure 5-5 as
follows:
a. Breaker open, closing springs discharged.
b. Breaker open, closing springs charged.
c. Breaker closed, closing springs discharged.
d. Breaker closed, closing springs charged.
The mechanism is a mechanically “trip-free” type. This means that if
an electrical or mechanical trip signal is present at the same time as
a close signal, the closing spring will discharge without causing a
closing direction movement in the primary circuit contacts.
In normal operation the closing spring is charged by the spring
charging motor, and the breaker is closed electrically by the
switchgear control circuit signal to energize the spring release coil.
Tripping is caused by energizing the trip coil through the control
circuit.
For maintenance inspection purposes the closing springs can be
charged manually by using the maintenance tool and the breaker can
be closed and tripped by pushing the “Push to Close” and “Push to
Open” buttons on the front panel.
WARNING
Figure 5-3 Ground Plate Alignment Check
