14
Instruction Book
IB182923EN September 2018 www.eaton.com
AMH-4.76-VR
+
VR-Series
+
Replacement Circuit Breaker
When the spring release clapper (Figure 4.5, Item 13) moves into
the face of the spring release coil (electrically or manually), the lower
portion of the clapper pushes the spring release latch (1) downward.
When the spring release latch moves, the cam shaft assembly is
free to rotate. The force of the closing cam (Figure 4.6.b, Item 5),
moving the main link (2), rotating the pole shaft (4) (which charges
the opening spring). This moves the three operating rods (3), closes
the main contacts and charges the contact loading springs (not
shown). The operational state immediately after the main contacts
close but before the spring charging motor recharges the closing
springs is illustrated in Figure 4.6.c. Interference of the trip “D”
shaft with the trip latch prevents the linkage from collapsing, and
holds the circuit breaker closed.
Figure 4.6.d shows the circuit breaker in the closed state after the
closing springs have been recharged. The recharging of the spring
rotates the closing cam one half turn. In this position the main link
roller rides on the cylindrical portion of the cam, and the main link
does not move out of position.
4.4.3 TRIPPING OPERATION
When the trip bar “D” shaft (Figure 4.6.b, Item 9) is turned by
movement of the shunt trip clapper (11), the trip latch will slip past
the straight cut portion of the trip bar shaft and will allow the banana
link and main link roller to lower. The energy of the opening spring
and contact loading springs is released to open the main contacts.
The mechanism is in the state illustrated (Figure 4.6.b) after the
circuit breaker is tripped open.
4.4.4 TRIP-FREE OPERATION
When the manual trip button is held depressed, any attempt to
close the circuit breaker results in the closing springs discharging
without movement of the pole shaft or vacuum interrupter stem.
4.5 CONTROL SCHEMES
There are two basic control schemes for the VR-Series
+
circuit
breaker elements, one for dc control and one for ac control voltages
(Figure 4.3). Specific customer order wiring schematics and
diagrams are included with each circuit breaker.
There may be different control voltages or more than one tripping
device, but the principal mode of operation is as follows:
As soon as the control power is applied, the spring charging motor
automatically starts charging the closing spring. When the springs
are charged, the motor cut off LS1/bb switch turns the motor off.
The circuit breaker may be closed by closing the control switch
close (CS/C) contact. Automatically upon closing of the circuit
breaker, the motor starts charging the closing springs. The circuit
breaker may be tripped any time by closing the control switch (CS/T)
contacts.
Note the position switch (PS1) contact in the spring release circuit
in the scheme. This contact remains closed while the circuit breaker
is being racked between the ‘Test’ and ‘Connect’ positions for
VR-Series
+
circuit breakers. Consequently, it prevents the circuit
breaker from closing automatically, even though the control close
contact may have been closed while the circuit breaker is racked to
the ‘Connect’ position.
When the CS/C contact is closed, the SR closes the circuit breaker.
If the CS/C contact is maintained after the circuit breaker closes, the
Y relay is picked up. The Y/a contact seals in Y until CS/C is opened.
The Y/b contact opens the SR circuit, so that even though the circuit
breaker would subsequently open, it could not be reclosed before
CS/C was released and remade. This is the anti-pump function.
4.5.1 TIMING
The opening and closing times for the circuit breakers vary
depending upon the control voltage, power rating, environment and
test equipment. Differences in timing are expected between initial
factory measurements and field inspections. Circuit breaker timing
can be measured by service personnel using available equipment
before installation and in conjunction with regular maintenance
periods to assist in tracking the general health of the circuit breaker.
Typical ranges as observed using nominal control voltages are listed
in Table 4.
Tablt 4. Timt Ptr Evtnt
Event
Milliseconds
Closing Time
(From Initiation of Close Signal to Contact Make)
45 - 60
Opening Time
(Initiation of Trip Signal to Contact Break)
30 - 38
Reclosing Time
(Initiation of Trip Signal to Contact Make)
140 - 165
otte:
N
Valuts art typical at nominal rattd control voltagt(s).
4.6 SECONDARY CONNECTION BLOCK
The breaker control circuit is connected to the switchgear control
through secondary connection block, located at the lower left
and right rear the circuit breaker (Figure Set 3.4). The contacts
engage automatically when the breaker is racked into the ‘Test’ and
‘Connect’ positions. The socket half of the connection is located in
the cubicle and a jumper of multiconductor cable can complete the
control connections (for testing) when the breaker is withdrawn
from the cell.
4.7 INTERLOCKS
m
DANGER
INTERLOCKS ARE PROTECTIVE DEVICES FOR PERSONNEL AND
EQUIPMENT. DO NOT BYPASS, MODIFY, OR DISABLE ANY INTERLOCKS.
DOING SO COULD CAUSE DEATH, SEVERE PERSONAL INJURY,
EQUIPMENT DAMAGE AND/OR IMPROPER OPERATION.
There are several interlocks built into the VR-Series
+
vacuum
replacement circuit breakers. Each of these interlocks, though
different in form, duplicate or exceed the function of the original
circuit breaker’s interlocks. These interlocks exist to safeguard
personnel and equipment. The basic premise behind the interlocking
arrangement on the vacuum replacement circuit breaker is that
the circuit breaker must not be inserted into or removed from a
live circuit while the main contacts are closed. Also considered in
the interlocking is that the circuit breaker should pose no greater
risk than necessary to the operator in or out of the circuit breaker
compartment.
4.7.1 ANTI-CLOSE INTERLOCK
The anti-close interlock prevents discharging of the closing springs if
the circuit breaker is already closed (Figure 4.5, Item 11). When the
circuit breaker is closed, the interlock component moves away from
the spring release clapper so that it cannot lift the spring release
latch (9).
4.7.2 RACKING SYSTEM TRIP AND SPRING RELEASE
INTERLOCKS
The racking interlock prevents engaging or disconnecting a closed
circuit breaker with live cell buss work or removing a mechanically
hazardous circuit breaker from the cell. The basic premise of this
interlock is that no circuit breaker should be connected to or
removed from cell primary circuitry when closed and no circuit
breaker should be removed from the cell with charged open or
closing springs. The racking interlock accomplishes this by providing
a trip signal to the circuit breaker automatically from the racking
mechanism interlock cams whenever the circuit breaker is in an
intermediate position in the cell and adding a close signal between
the DISCONNECT and WITHDRAWN positions to render the circuit
breaker trip-free prior to leaving the cell (close and open springs
discharged).
