Powered by Safety
®
17
Equipment Description
01.4IB.77000B
b. Interlocking
PowlVac-ND® circuit breakers are
provided with several interlocks that
operate in conjunction with the circuit
breaker compartment to ensure the
proper operation of the circuit breaker.
Do not attempt to modify or bypass
these interlocks, as they are necessary
for the safe operation of the circuit
breaker. The following describes the
interlocking for the closed door racking
circuit breaker:
The purpose of the interlocks is to
ensure:
• The circuit breaker cannot be moved
from the test/disconnected to the
connected position unless the main
circuit breaker contacts are opened
and the secondary control circuitry
from the compartment to the
circuit breaker is completed, and
the circuit breaker cannot be
removed from the connected to
the test/disconnected position
unless the main contacts are
opened.
• The control circuits cannot be
broken when the circuit breaker is in
the connected position.
• The circuit breaker cannot be
removed from the circuit breaker
compartment with the circuit
breaker closed or with the main
closing spring charged.
Closed Door Racking (CDR) circuit
breaker interlocking is primarily
achieved by means of an interlock bar
acting upon the racking drive shaft
extension, an interlock bar attached to
the secondary disconnect receptacle,
and a tripping linkage and roller on
the right side of the frame of the circuit
breaker that interfaces with the circuit
breaker compartment.
An interlock bar prevents the rotation
of the racking drive shaft extension
whenever the circuit breaker is closed
or the secondary disconnect plug is
removed. This prevents movement
of the circuit breaker when the circuit
breaker is closed, or when the control
circuits are disconnected.
Racking the circuit breaker in from
the test/disconnected position to the
connected position also rotates a cam
attached to the racking shaft. A cam
follower, attached to a lever pivoted
on the circuit breaker frame, drives
a secondary disconnect locking bar
downward. The locking bar engages a
slot in the interlock bar attached to the
secondary disconnect plug. The cam
profile is arranged so that the lever can
only be in its upward position when the
racking crank arms are fully in the
test/disconnected position.
This ensures that the control circuits
cannot be disconnected in any position
except the test/disconnected position.
The tripping linkage and roller on
the side of the circuit breaker frame
follows a cam mounted in the circuit
breaker compartment. The cam, in
all intermediate positions between
the test/disconnected and connected
position, depresses the tripping roller.
Depressing the tripping roller actuates
the manual trip operator which holds
the breaker in a trip free condition. The
manual trip operator also actuates the
latch check switch, thus blocking any
electrical closing signal.
