18
Instruction Book
IB182012EN March 2017 www.eaton.com
50DH-VR-50AXU / 50XU / 75U / 75ARU - 600 / 1200A
Replacement Circuit Breaker
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 4.6) 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”.
Figure 4.6. Front Racking - Connect (Position F)
Figure 4.7. Rear Racking - Disconnect (Position B)
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.
Position J:
Once the racking mechanism is racked
counterclockwise until a mechanical stop is reached it is in the
disconnected position. The racking handle should be removed at this
point. The circuit breaker is ready to be removed from the switchgear
if desired.
Position K:
The circuit breaker is removed from the switchgear
by manually pulling on the handle located immediately below
the position mode indicator. The racking system is in the
“DISCONNECT” orientation. The circuit breaker is in a trip-free
status and in a non-operable state in the withdrawn position.
4.13.2 50DH-VR 50XU / 75ARU - REAR RACKING
Position A:
This is the “WITHDRAWN” position. In the
“WITHDRAWN” position the circuit breaker is out of the switchgear.
The racking handle is not required for this position and the racking
system interlocks are not automatic outside the switchgear. The
circuit breaker is in a trip-free state and cannot be operated.
Position B:
(Figure 4.7) As the circuit breaker is pushed into the
cell, all four wheels will be on the cell floor.
