TYPE KA CARRIER AUXILIARY RELAY
183A435
Fig. 2. Internal Schematic of the Type
KA
Relay in Type
FT 32 Case.
on the operating
cr.
The primary of the transformer is tapped and
brought out to a tap connector block for ease in
changing the pick-up current of the relay. The use of
a tapped transformer provides approximately the same
energy level at a given multiple of pick-up current
for any tap setting, resulting in one time curve
throughout the range of the relay.
Across the secondary is connected a non-linear
resistor known
as
a varistor.
The effect of the
varistor is to reduce the voltage peaks applied to the
overcurrent unit and phase shifting capacitor.
�
irectional Auxiliary Units
These are tw'o solenoid-type contactor switches
designated as CSP and CSG.
The phmger of the
contactor switch has a circular conducting disc
mounted on its lower end and as the plunger travels
upward, the disc bridges three silver stationary con
tacts. The CSP switch is energized by the operation
of the second zone unit of the KD distance relay,
and the CSG switch, by the operation of the direction
al
and overcurrent units of the ground relay. The
contacts of the two switches are connected in parallel
as shown in the internal schematic. The operation of
40
36
::
32
-
�
28
"'
:::
ii
24
!!!
...
20
-
;:::
�
15
ii
�
C>
.
12
-
u
-c
:;;;
C>
u
0
0
10
12
14
II
18
20
MULTIPLES
or
PICKUP CURREIT
or
CARRIER- START OYERCURREIT
um
Curve
471o61
Fig. 3. Typical Time Characteristics of carrier start over
current unit of the type
KA
Relay.
either of these switches connects the carrier control
circuit to negative
to
stop carrier, and energizes the
RRT operating coil of the receiver relay unit.
Receiver Uni t
The polarized relay consists of an armature and
contacts mounted on a leaf spring supported sym
metrically within a magnet frame. The armature rides
in the front air gap of the frame with the contacts
projecting outside. The poles of a permanent magnet
clamp directly to each side of the frame. Two ad
justable shunts are located across the rear air gaps.
These change the reluctance of the magnetic path as
shown in Fig.
4
so as to force some of the flux thru
the moving armature which is fastened to the frame
midway between the two rear
air
gaps. Flux in the
armature polarizes it and creates a magnetic bias,
causing it to move towards either the left or right,
depending upon the adjustment.
Two stationary contact screws are mounted to the
left (front view) of the moving contact assembly and
adjusted for normally open contacts.
These con
tacts are designated, RRP and RRG, and are connected
in the phase and ground trip circuits respectively.
These contacts are operated by two concentric coils,
RRT and RRH, which are placed around the armature
3
www
. ElectricalPartManuals
. com
