43
Closed Breaker Racking Interlock
The closed breaker racking interlock is designed to prevent a
breaker from being racked from TEST to CONNECT and vice-versa
with the primary contacts closed. Only an open circuit breaker
is to be moved between these positions. Refer to
Figure 45.
The trip free interlock slide has angle-shaped members
(
Figure 45
, item 60) that project from the left side of the racking
mechanism and engage an interlock member from the circuit
breaker. The circuit breaker interlock extends down to prevent
movement of the trip free interlock slide with the circuit breaker
closed. When engaged, the racking screw is not accessible to
the racking crank until the breaker has been opened.
Note:
Racking handle must be removed, allowing the interlock
slides to return to their initial position. The breaker may now
be closed mechanically or electrically.
Racking Access Interlock
The racking interlock slide (
Figure 45
, item 62) has provisions
for three padlocks to prevent engagement of the racking crank to
the racking screw. This allows locking of the circuit breaker in
DISCONNECT, TEST, or CONNECT positions. Key interlocking
(
Figure 45
, item 42) can be provided for racking sequence
interlocking of dummy breakers, etc. When the key interlock
bolt (on key interlock item 42) is extended, the racking inter-
lock slide (item 62) is held in place, preventing access to the
racking screw, thus preventing racking. When locked in the
DISCONNECT position, the circuit breaker or dummy can be
removed for servicing.
Figure 45.
Racking Mechanism and Interlocks
Figure 46.
Trip Free Interlock Positions (Viewed from left side
of circuit breaker)
Trip-Free Interlock
The trip-free interlock slide prevents a circuit breaker from
being closed between the TEST and CONNECT positions by
maintaining a mechanical and electrical trip-free condition
(
Figure 46
).
As the breaker moves between the TEST and CONNECT
positions, the trip-free roller engages the trip-free rail of the
racking device. As the roller travels the trip-free rail between
positions, the roller activates the trip linkage which holds the
circuit breaker in a mechanically trip-free condition.
In order to lock the circuit breaker trip-free in either the TEST
or CONNECT positions, the breaker must be opened and the
trip-free interlock slide assembly pushed forward to lift the trip-
free roller on the breaker. This position permits the use of a
key interlock (
Figure 45
, item 41) or padlocks (up to 3) to maintain
the mechanism in trip-free position. The circuit breaker can be
removed for servicing while interlocked in the trip-free position.
The interlock can be tested by racking the circuit breaker to a
position between the TEST and CONNECT position with the
closing springs charged. Activating the “close” function manu-
ally will cause the springs to discharge and the interlock
should prevent the circuit breaker from closing. Activating the
“close” function electrically (such as by using the control
switch) should cause no operation. This is also true when the
breaker is in either the TEST or CONNECT positions and the
trip-free interlock slide is pushed forward and key interlocked
or padlocked. The breaker will operated trip-free when closing
is attempted.
Spring Discharge Interlock
The closing spring discharge interlock prevents the insertion or
removal of a circuit breaker with a charged mechanism. The
spring dump roller rides up a rail releasing the closing springs
while held trip-free. This discharges the closing springs with-
out closing the breaker primary contacts. (
Figure 33
).
CONNECT
POSITION
TEST
POSITION
DISCONNECT
POSITION
TRIP
FREE
CONNECT POSITION
OF BREAKER
TRIP FREE ROLLER
ASSEMBLY ON BREAKER
TEST POSITION
OF BREAKER
DISCONNECT POSITION
OF BREAKER
TRIP FREE
INTERLOCK SLIDE
0.1
0.5
0.18
0.12
0.0
0.0
0.13
0.1
0.05
35.096
21.857
5.028
10.531
3.276
24.076
CENTER
62
60
WITHOUT KEY INTERLOCKS
42
41
WITH KEY INTERLOCKS
Circuit Breaker Position
Note 1:
Racking padlock provisions– when padlocked, prevents racking
of circuit breaker, test device, or dummy breaker element. Suitable for
up to three padlocks with up to 3/8” diameter shackle.
Note 2:
Trip-free padlock provisions– when padlocked, prevents closing
of circuit breaker or test device. suitable for up to three padlocks with
up to 3/8” diameter shackle.
Racking padlock provisions (Note 1)
Trip-free padlock
provisions (Note 2)