17
Instruction Book
IB182012EN March 2017 www.eaton.com
50DH-VR-50AXU / 50XU / 75U / 75ARU - 600 / 1200A
Replacement Circuit Breaker
4.12.1 RACKING SYSTEM TRIP AND CLOSING SPRING
RELEASE INTERLOCKS
The racking system tripping and spring release interlocks perform
the following:
•
Sets the circuit breaker mechanically trip-free whenever the
circuit breaker is in the “WITHDRAWN” position or between the
“TEST” and “CONNECT” positions.
•
Set the circuit breaker in a safe condition (circuit breaker open,
springs discharged) when removed from the cell.
•
Insert a mechanical trip signal to open a position switch
preventing energization of the spring release coil whenever the
circuit breaker is in the “WITHDRAWN” or “DISCONNECT”
positions or in an intermediate position.
•
Prevents inadvertent cycling (pumping) of the circuit breaker
between the “TEST” or “CONNECT” positions.
Prevents insertion of a closed and/or charged circuit breaker into a
cell.
INSERTING BREAKER
REMOVING BREAKER
POSITION MODE INDICATOR
LEGEND
FORCED CLOSE AND
FORCED TRIP FREE STATE
BREAKER CAN BE
CLOSED AND/OR OPENED
FORCED TRIP
FREE STATE
TRIP FREE
TEST/OPERATE
TRIP FREE
TEST/OPERATE
PUSH/PULL
WITHDRAWN
TEST
DISC.
INTERMEDIATE
CONNECTED
LEVERING CRANK USED BETWEEN THESE POSITIONS
A
K
B
J
C
I
D
H
E
G
F
06219502
Figure 4.3. Cell Position Description
4.13 CELL POSITION DESCRIPTION
4.13.1 50DH-VR 50AXU / 75U - FRONT 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This is the “WITHDRAWN” position.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“WITHDRAWN” position the circuit breaker is out of the switchgear.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 4.4) As the circuit breaker is pushed
into the switchgear it will reach a mechanical stop. This is the
“DISCONNECT” position and the circuit breaker is still in the trip-
free state and cannot be operated. Although it is possible to engage
the secondary disconnect block in this position, it SHOULD NOT BE
engaged at this time.
Position C:
The racking handle is inserted on the racking shaft and
turned in a clockwise direction. The circuit breaker starts advancing
into the switchgear. The circuit breaker remains in the trip-free state
until “Position D” is reached.
Position D:
(Figure 4.5) Continue turning the racking handle in
the clockwise direction for approximately 2 turns. 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. Observe the shutter
position indicator which is located inside of the switchgear structure.
Continue turning the racking handle until the shutter indicator begins
to move downward. Stop clockwise rotation at this point. Turn the
racking handle counter-clockwise to return the shutter to its fully
closed position. 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
Figure 4.4. Front Racking - Disconnect (Position B)
Figure 4.5. Front Racking - Test (Position D)
