I.L. 41-748.1F
3
2.2.
AUTOTRANSFORMER
The autotransformer has three taps on its main wind-
ing, S, which are numbered 1,2, and 3 on the tap
block. A tertiary winding M has four taps which may
be connected additively or subtractively to inversely
modify the S setting by any value from -15 to +15
percent in steps of 3 percent.
The autotransformer makes it possible to expand the
basic ranges of the long and short reach compensa-
tors by a multiplier of
. Any relay ohm setting
can be made within
±
1.5 percent from 2.08 ohms to
56 ohms for the long reach and from .79 ohms to 18
ohms for the short reach.
2.3.
IMPEDANCE TRIPPING UNIT
The distance unit is a four-pole induction cylinder
type unit. The operating torque of the unit is propor-
tional to the product of the voltage quantities applied
to the unit and the sine of the phase angle between
the applied voltages. The direction of the torque so
produced depends on the impedance vector seen by
the relay with respect to its characteristic circle.
Mechanically, the cylinder unit is composed of four
basic components: A die-cast aluminum frame, an
electromagnet, a moving element assembly, and a
molded bridge. The frame serves as a mounting
structure for the magnetic core. The magnetic core
which houses the lower pin bearing is secured to the
frame by a locking nut. The bearing can be replaced,
if necessary, without having to remove the magnetic
core from the frame.
The electromagnet has two sets of two series-con-
nected coils mounted diametrically opposite one
another to excite each set of poles. Locating pins on
the electromagnet are used to accurately position the
lower pin bearing, which is mounted on the frame,
with respect to the upper pin bearing, which is
threaded into the bridge. The electromagnet is
secured by the frame by four mounting screws.
The moving element assembly consists of a spiral
spring, contact carrying member, and an aluminum
cylinder assembled to a molded hub which holds the
shaft. The hub to which the moving-contact arm is
clamped has a wedge-and-cam construction, to pro-
vide low-bounce contact action. A casual inspection
of the assembly might lead one to think that the con-
tact arm bracket does not clamp on the hub as tightly
as it should. However, this adjustment is accurately
made at the factory and is locked in place with a lock
nut and should not be changed. Optimum contact
action is obtained when a force of 4 to 10 grams
S
1
M
±
--------------
Figure 2. Compensator Construction
Figure 3. Internal Schematic of Type KFL-1
Relay in FT41 Case
185A181
187A724
TELEPHONE RELAY
ICS
INDICATING
CONTACTOR
SWITCH
500 D -48 Vdc
2000 D -125 Vdc
6000 D - 250 Vdc
UNDER VOLTAGE UNIT
(LOWER UNT)
LONG REACH
COMPENSATOR
IMPEDANCE UNIT
(CENTER UNIT)
SHORT REACH
COMPENSATOR
LONG REACH
COMPENSATOR
REVERSING LINKS
DIRECTIONAL UNIT
(TOP UNIT)
CHASSIS OPERATED
SHORTING SWITCH
RED HANDLE
CURRENT JACK
TEST SWITCH
TERMINAL
With relative
instantaneous polarities
as shown the directional
contacts closed.
