Operation - ABB D-3 Instructions Manual

41-151.1H
Figure 1: Schematic Drawing of Magnetic Circuit of Type
D-3 Relay (Top View). Moving Coil Bearing Sup-
ports, Springs and Contacts Omitted.
2.2 MOVING COIL
The moving coil rotates in the air gap between the
core and the iron frame. Electrical connections are
made to the coil through two springs located at the
top of the element. One end of each spring is con-
nected through a lever am to a head of the coil.
cache other end of each spring is fastened to posts
mounted in a circular insulation plate. This plate can
be rotated to permit adjustment of the zero position
of the moving element.
A third spiral spring located at the bottom of the ele-
ment provides a current path to the moving contact.
2.3 AUXILIARY SWITCH (CS-1) (WHEN USED)
The auxiliary switch is a small solenoid type switch. A
cylindrical plunger with a silver disc mounted on its
lower end moves in the core of the solenoid. As the
plunger travels upward the disc bridges three silver
stationary contacts.
2.4 OPERATION INDICATOR (WHEN USED)
The operation indicator consists of a small solenoid
coil mounted in a steel frame, a spring restrained
armature and a white flag. The indicator is reset by a
push rod in the cover.
2
Sketch
205342
Figure 2: Internal Schematic of the Type D-3 Relay in the
Type FT-21 Case.

3.0 OPERATION

The D-3 relay operates on the principle of a current
carrying conductor (moving coil) located in a mag-
netic field (permanent magnet). When a current is
applied to the coil of the relay, a torque is produced
that rotates the moving coil until the electrical torque
is equal to the torque of the restraining spring. The
moving contact will assume a position in its travel
that is proportional to the current applied to the mov-
ing coil.
The direction of movement of the moving coil is
determined by the polarity of the current applied to
the roil. In the "left zero" and "suppressed zero" D-3
relays, the contacts will move to the right when a cur-
rent of the proper magnitude and polarity is applied
to the relay. On the other hand, the contact of the
"center zero" relay will move either left or right
depending on the polarity and magnitude of the
applied current.
4.0 CHARACTERISTICS
The type D-3 relay is supplied in the standard ranges
listed in the table below. The numbers on the scale
indicate in millivolts the potential required at the relay
base terminals to operate the moving element to the
indicated scale position.
Type D-3 Direct Current Relay
182A787