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1.0
2.0
4.0
3.0
5.0
6.0
8.0 9.0
7.0
9.0
8.0
10.0
Figure 31: Closed circuit breaker interlock mechanism in stored-energy mechanism
34
1.0
Close-latch lever
2.0
Closing-spring release cam
3.0
Normal operating position
4.0
Trip-latch lever
5.0
Trip-free pushrod
6.0
Trip-pushrod cam
7.0
Enclosure rear
8.0
Interlock levers
9.0
Retaining rings
10.0
Spring-dump tube
B. Type GMSG-GCB (not type GMSG)
generator circuit breaker rating
interlocks
Type GMSG-GCB (not type GMSG)
generator circuit breakers rated 40 kA
are designed such that the circuit
breaker can be installed in a generator
circuit breaker cell rated 40 kA of equal
or lower continuous current rating.
Type GMSG-GCB generator circuit
breakers rated 50 kA or 63 kA are
designed such that the circuit breaker
can be installed in a generator circuit
breaker cell of equal or lower
interrupting rating, and equal or lower
continuous current rating.
2. Racking interlocks
A. CLOSED circuit breaker interlock
Figure 28: Circuit breaker interlocks and
ground disconnect on page 29 shows
the location of the CLOSED circuit
breaker interlock-plunger on the circuit
breaker frame.
The purpose of this interlock is to
positively block circuit breaker racking-
operations whenever the circuit breaker
is CLOSED. The plunger is coupled to
the jack shaft as seen in Figure 15:
Stored-energy operating mechanism,
item 63 on page 20. When the jack
shaft rotates to close, the interlock
plunger is driven straight downward
beneath the frame of the circuit
breaker. The downward projecting
plunger blocks racking operation when
the circuit breaker is CLOSED.
Figure 29: Circuit breaker compartment
(up to 50 kA shown) on page 30 shows
the racking mechanism located on the
floor in the center of the circuit breaker
compartment. Note the two "wing-like"
elements that project from the right
side of the racking mechanism. The
CLOSED circuit breaker interlock
plunger, when down (circuit breaker
CLOSED), falls behind the front wing in
the TEST position and behind the rear
wing in the CONNECT position.
The wings are coupled to the element
of the racking mechanism that shrouds
the racking screw. This shroud must be
moved rearward to insert the racking-
crank socket in order to engage the
racking shaft. With the plunger down
(circuit breaker CLOSED), the wings and
shroud cannot be moved and thus
racking is blocked.
B. Trip-free interlock
Figure 28: Circuit breaker interlocks and
ground disconnect on page 30 shows
the automatic closing spring energy
released (spring dump) and trip-free
interlock. This interlock is a plunger
with a roller on the lower end. The
plunger roller tracks the shape of the
cam profiles on the racking mechanism
in the switchgear (refer to Figure 29:
Circuit breaker compartment (up to
50 kA shown) on page 30).
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