Undervoltage Trip A Ttachment 2; Reverse Current Trip Attachment - Westinghouse DB-50 Instructions Manual

Page 26
Maintenance
Check for loose bolts and faulty coil.
UNDERVOLTAGE TRIP ATTACHMENT
The undervoltage trip mounts on top of the
platform, to the right of the shunt trip .
.
(See Fig. 1 7 ) Its function is to trip the
breaker when the voltage falls to between
30 to 60 percent of normal.
The moving core is normally held mag­
netically against the stationary core to hold
the rod and consequently the reset lever in
the reset position. When the coil voltage is
reduced sufficiently, the reset lever spring
overcomes the magnetic attraction of the
cores and rotates reset lever clockwise .
As reset lever rotates, pin pushes against
the latch to release it from its latch plate .
When the latch releases, the trip spring
rotates the trip lever counterclockwise to
trip the breaker. The linkage is reset by
the cross bar as the breaker opens.
Always connect the coil to the line side
of the breaker unless the attachment is
equipped with a time delay device . In this
case, the time delay will delay the tripping
of the breaker long enough to permit ener­
gization of the undervoltage coil from the
Do not use an auxiliary switch
load side .
contact in the undervoltage circuit.
UNDERVOLTAGE TIME DE LAY
ATTACHMENT
The undervoltage air dashpot time delay
attachment mounts on the front of the under­
voltage trip, replacing moving core cover.
(See Fig. 17 .) The needle valve screw in the
top regulates the opening through which the
air is forced and hence the time delay. (See
Fig. 1 8.) The attachment does not have a
quick reset feature and therefore approx­
imately one minute should be allowed be­
tween operations to permit complete re­
setting. It is set to trip within 4 to 7 seconds.
Inspection
Hold the trip bar down and close the breaker
manually. Release the trip bar slowly,
allowing the undervoltage trip spring to
raise the trip bar and trip the breaker.
Maintenance
Check for loose bolts and faulty coils.
REVERSE CURRENT TRIP
ATTACHMENT
This attachment mounts directly on the
center molded pole unit base, in the space
ordinarily occupied by the overcurrent at­
tachment. (See Fig. 1 9 .) It is used to trip
the breaker when the direction of current
flow in that pole is reversed.
series coil current is flowing in the forward
direction, armature movement is prevented
by a stop . When the series coil current is
reversed, the armature rotates in the op­
posite direction to trip the breaker. Cali­
bration adjustment covers 5 and 25 percent
reverse current, based on normal current
rating.
After tripping the reverse current arma­
ture is reset by opening the potential coil
circuit. For this purpose an " a" contact of
the breaker auxiliary switch should be con­
nected in series with the potential coil .
Inspection
Close the breaker manually, and push back­
ward on the spring stud located on the bottom
of the armature, to trip the breaker. The
armature should move without friction, and
should have approximately 1 / 32-inch over­
travel after tripping.
Final inspection should be made elec­
trically, after the circuit connections are
complete as shown in Fig. 2 , Page 1 0 .
Maintenance
Remove all power from the breaker and
repeat the mechanical inspection given
above . Check for loose bolts and open cir­
cuit in potential coil .
When the