Eaton VR+ Series, Instruction Book

13

Instruction Book    

IB182923EN   September 2018   www.eaton.com

AMH-4.76-VR

+

VR-Series

+ 

 Replacement Circuit Breaker

m

 DANGER

FAILURE TO REPLACE THE VACUUM INTERRUPTER ASSEMBLY WHEN 

INDICATED BY THE CONTACT EROSION INDICATOR COULD CAUSE THE 

CIRCUIT BREAKER TO FAIL, LEADING TO DEATH, SEVERE PERSONAL 

INJURY, EQUIPMENT DAMAGE AND/OR IMPROPER OPERATION.

4.1.3   CONTACT WIPE AND STROKE

The circuit breaker mechanism provides a fixed amount of motion 

to the operating rods connected to the moving stem of the vacuum 

interrupter. The first portion of the motion, the stroke, is used to 

close the vacuum interrupter contacts; the remainder of that motion, 

the wipe, is used to further compress the pre-loaded wipe spring. 

Contact stroke and wipe are related; contact wipe is the indication 

of the force holding the vacuum interrupter contacts closed as well 

as the energy available to hammer the contacts open with sufficient 

speed for interruption. Stroke is the gap between the stationary and 

moving contact of the vacuum interrupter when the circuit breaker 

is open. As the stroke increases due to contact erosion inside the 

vacuum interrupter, the wipe decreases. Although these changes 

are taking place as operations accumulate on the vacuum interrupter, 

field adjustment of the wipe or stroke are not necessary during the 

lifetime of the vacuum interrupter. 

m

 WARNING

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.

4.2   PHASE BARRIERS

Phase barriers are sheets of insulation located between the 

interrupter pole assemblies and on the sides of the breaker frame. 

The phase barriers are designed to isolate energized conductor 

components in each phase from the adjacent phase and ground.

m

 WARNING

ALL 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.

4.3   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 

conductors. Solid stab type primary disconnecting contacts at 

the ends of the conductors provide means for connecting and 

disconnecting the circuit breaker to the bus terminals in the 

switchgear compartment.

4.4   STORED ENERGY MECHANISM

The spring-type stored energy operating mechanism is mounted 

on the circuit breaker frame and in the front of the circuit breaker. 

Manual closing and opening controls are at the front cover (Figure 

Set 3.3). They are accessible while the circuit breaker is in any of its 

basic installation positions. (See Section 5 in this manual)
The mechanism stores the closing energy by charging the closing 

springs. Spring charging is automatically accomplished when control 

power is applied to the circuit breaker secondary disconnect contact. 

When released, the stored energy closes the circuit breaker, charges 

the wipe and resets the opening springs. The mechanism may rest 

in any one of the four positions shown in Figure 4.6 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.

m

 DANGER

KEEP HANDS AND FINGERS AWAY FROM CIRCUIT BREAKER’S INTERNAL 

PARTS WHILE THE CIRCUIT BREAKER CONTACTS ARE CLOSED OR THE 

CLOSING SPRINGS ARE CHARGED. THE CIRCUIT BREAKER CONTACTS 

MAY OPEN OR THE CLOSING SPRINGS DISCHARGE CAUSING CRUSHING 

INJURY. DISCHARGE THE SPRINGS AND OPEN THE CIRCUIT BREAKER 

BEFORE PERFORMING ANY MAINTENANCE, INSPECTION OR REPAIR ON 

THE CIRCUIT BREAKER.

THE DESIGN OF THIS CIRCUIT BREAKER ALLOWS MECHANICAL CLOSING 

AND TRIPPING OF THE CIRCUIT BREAKER WHILE IT IS IN THE ‘CONNECT’ 

POSITION. HOWEVER, THE CIRCUIT BREAKER SHOULD BE CLOSED 

MECHANICALLY ONLY IF THERE IS POSITIVE VERIFICATION THAT LOAD 

SIDE CONDITIONS PERMIT. IT IS RECOMMENDED THAT CLOSING THE 

CIRCUIT BREAKER IN THE ‘CONNECT’ POSITION ALWAYS BE DONE WITH 

THE CUBICLE DOOR CLOSED. FAILURE TO FOLLOW THESE DIRECTIONS 

MAY CAUSE DEATH, SEVERE PERSONAL INJURY, EQUIPMENT DAMAGE 

AND/OR IMPROPER OPERATION.

ELECTRICAL TRIPPING CAN BE VERIFIED WHEN THE CIRCUIT BREAKER IS 

IN THE ‘DISCONNECT / TEST’ POSITION.

4.4.1   CLOSING SPRING CHARGING

Figure 4.5 shows schematic section views 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 shaft to which are attached two closing spring 

cranks (one on each end), the closing cam, drive plate, and a free-

wheeling ratchet wheel.
The ratchet wheel (6) is actuated by an oscillating ratchet lever 

(12) and drive pawl (10) driven by the motor eccentric cam. As the 

ratchet wheel rotates, it pushes the drive plates which in turn rotate 

the closing spring cranks and the closing cam on the cam shaft. 

The motor will continue to run until the limit switch “LS” contact 

disconnects the motor.
The closing spring cranks have spring ends connected to them, 

which are in turn coupled to the closing springs. As the cranks 

rotate, the closing springs get charged.
The closing springs are completely charged, when the spring cranks 

go over dead center and the closing stop roller (9) comes against the 

spring release latch (1). The closing springs are now held in the fully 

charged position.
The closing springs may also be charged manually as follows: Insert 

the end of the maintenance tool into the manual charge socket 

opening and charge the closing springs by moving the handle up 

and down the full range of motion. When charging is complete the 

ratchet will no longer advance and the spring charged / discharged 

indicator displays ‘Charged’. (Figure Set 3.3). Any further motion of 

the maintenance tool will not result into advance of charging.

4.4.2   CLOSING OPERATION

Figure 4.6 shows the positions of the closing cam and tripping 

linkage for four different operational states. In Figure 4.6.a the 

circuit breaker is open and the closing springs are not charged. In 

this state, the trip latch (8) is disengaged from the trip “D” shaft (9) 

(unlatched). After the closing springs become charged, the trip latch 

snaps into the fully reset or latched position (Figure 4.6.b)

The mechanism is a mechanically “trip-free” design. Trip-free is 

defined in Section 4.3.4 (Trip-Free Operation).
In normal operation the closing spring is charged by the spring 

charging motor, and the circuit 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 circuit 

breaker can be closed and tripped by pushing the “Push to Close” 

and “Push to Open” operators on the front cover.