19
Instruction Book
IB182012EN March 2017 www.eaton.com
50DH-VR-50AXU / 50XU / 75U / 75ARU - 600 / 1200A
Replacement Circuit Breaker
Figure 4.9. Rear Racking - Connect (Position F)
Figure 4.8. Rear Racking - Test (Position D)
Position C:
Continue to push the circuit breaker into the
switchgear until the racking arm rollers engage the guide rails. The
shutters will start to rise. The circuit breaker remains in the trip-free
state until “Position D” is reached.
Position D:
(Figure 4.8) Insert the racking handle and rotate
clockwise approximately one turn. At this time, note that the circuit
breaker position mode indicator status will change from “TRIP-
FREE” to “TRIP/OPERATE”. There is no click, stop or different
feel to the racking handle at this point. The circuit breaker is now
in its “TEST” position. After reaching the test position, REMOVE
the racking handle. In the “TEST” position, the circuit breaker
can be closed and tripped manually and electrically, thus allowing
maintenance tests or checks. To operate the circuit breaker
electrically, the secondary disconnect block must be engaged at this
time. Release the secondary disconnect block slider by pulling the
release pin and pushing the slider toward the rear several inches.
The slider is located on the lower left hand area of the circuit breaker
frame. Push on the front side flat surface of the slider until the
secondary disconnect block can be felt to be fully engaged in the
secondary disconnect block’s socket. The spring charging motor
will begin to run and charge the closing spring as the secondary
disconnect block engages. The circuit breaker is now in the “TEST”
position, with control voltage applied, and ready for testing. The
circuit breaker is held captive in the switchgear via the racking
system.
Position E:
To continue installing the circuit breaker to the
connected position the racking handle will have to be reinserted onto
the racking shaft (the circuit breaker MUST be in the open position).
Continue turning the racking handle in the clockwise direction and
the circuit breaker will continue advancing into the switchgear.
The position mode indicator will change from “TEST/OPERATE” to
“TRIP-FREE”. The racking system cam will engage the trip release
mechanism. The circuit breaker will not be able to mechanically
close in this position. As you continue to advance the circuit breaker
into the switchgear the primary voltage source shutters will open
allowing the circuit breaker stabs to engage with the source.
Position F:
(Figure 4.9) Continue the clockwise rotation of the
racking handle until a mechanical stop is reached. This is the fully
engaged or connected position. At this position you will note the
position mode indicator is again on “TEST/OPERATE”, the trip and
close cams have released the trip and close mechanisms, and the
circuit breaker can be operated. The circuit breaker is now ready for
service.
WARNING
DO NOT USE ANY TOOL TO RACK THE CIRCUIT BREAKER TO OR FROM THE
CONNECTED POSITION OTHER THAN THE RACKING HANDLE.
Position G:
Insert the racking handle onto the racking shaft. Turn
the racking handle in the counterclockwise direction. The circuit
breaker will start coming out of the switchgear but before the
main stabs are disconnected, the racking cam will raise the trip
mechanism, putting the circuit breaker into the trip-free state. Also,
the secondary disconnect will disengage automatically. The position
mode indicator will change from “TEST/OPERATE” to “TRIP-FREE”.
The circuit breaker is in a non-operable mode and will go through a
trip-free operation if an attempt to close it were made.
Position H:
Continue racking in the counterclockwise direction, and
the shutters will close after the main stabs have cleared, isolating
the circuit breaker from its source. Continue racking until the
position mode indicator re-centers on “TEST/OPERATE”. At this time
the circuit breaker is in the test position and the trip mechanism
is released, allowing the circuit breaker to be operated either
electrically or mechanically. To operate electrically, the secondary
disconnect block must be re-engaged.
Position I:
To remove the circuit breaker from the test position to
the disconnect, the circuit breaker must be tripped if closed, and the
secondary disconnect block should be disengaged and the manual
open and close buttons cycled to render the circuit breaker open and
discharged. Continued racking will force a trip-free condition leaving
the circuit breaker in the open position if the circuit breaker were left
closed in the test position. The circuit breaker is in a non-operable
state.
