GE STD15C - MAIN OPERATING UNIT; TARGET AND SEAL-IN UNIT; CASE

GEK—45307
overcurrent
unit
operation.
Pickup
is
set above
the level
of
differential
current
produced
by
maximum
magnetizing
inrush
current.
Figure
5
shows
the
relative
levels
of
pickup
and
speed
of operation
of
the main
unit
and
the
overcurrent
unit.
MAIN
OPERATING
UNIT
The
primary
functioning
unit
of
the
STD
relay
is
a
solid-state amplifier,
whose
output
controls
a
simple
telephone
relay.
The sense
amplifier
is
shown
in
Figures
10
and
11
as
a large
rectangle. The amplifier
consists
of
many
electronic
components
mounted
on
a printed
circuit
card
in
the
top
half
of
the relay.
This
printed
circuit
card
is
installed
in
a
ten-prong
printed
card
design
socket.
A
schematic
of
this card
is
shown
in
Figure
9.
This
component
is adjusted
prior
to
leaving
the
factory,
and
should
require
no
further
attention.
The
telephone-type relay
is
mounted
vertically
in
the
mid-section
of the
relay.
It,
too,
has
been
carefully
adjusted
at
the
factory,
and
should
require
no
further
attention.
If
this
small
relay
has
been
disturbed,
refer
to the
section
under
ADJUSTMENTS.
TARGET
AND
SEAL-IN
UNIT
There
is
a
target
and seal-in
unit
mounted
on
the top
left
of the
relay.
This
unit
has
its
coil
in series
and
its contacts
in parallel
with
the main
contacts
of
the
telephone—type relay.
When
the
telephone—type
relay
contacts
close,
the
seal-in
unit
operates, raising
its
target
into
view
and
sealing
around
the
telephone-type
contacts.
The
target
of
this
unit
will
remain
exposed
until
released
by
pushing
a
button
beneath
the lower
left corner
of
the
cover
of
the relay
case.
CASE
The
case
is
suitable
for
surface
or
semi-flush
panel
mounting,
and
an
assortment
of
hardware
is provided
for
either
method.
The
cover
attaches
to
the case,
and carries
the
target
reset
mechanism
for
the
trip
indicator
and
instantaneous unit.
Each
cover
screw
has
provision
for
a
sealing
wire.
The
case
has
studs
or
screw
connections
at
the
bottom
for
the
external
connections.
The
electrical
connections
between
the
relay
unit
and
the
case
studs
are
made
through
spring—backed
contact
fingers
mounted
in
stationary
molded
inner
and
outer
blocks,
between
which
rests
a
removable
connecting
plug that
completes
the
circuit.
The
outer
block,
attached
to
the case,
holds
the
studs
for
the
external
connections,
and
the inner
block
has
terminals for
the internal
connections.
The
relay
mechanism
is
mounted
in
a
steel
framework
called
the
cradle,
and
is
a
complete
unit,
with
all leads
terminating
at
the
inner
block.
This
cradle
is held
firmly
in
the
case
by a latch
at
the
top
and bottom
and
a
guide
pin
at
the
back of
the
case.
The
case
and
cradle
are
so constructed
that
the
relay
cannot
be inserted
in
the
case
upside
down.
The
connecting
plug,
besides
making
the
electrical
connection
between
the
blocks
of
the
cradle
and
case,
also
locks
the latch
in
place.
The
cover,
which
is
fastened
to
the
case
by thumbscrews,
holds
the
connecting
plug
in
place.
To
draw
out
the
relay
unit,
the
cover
is
removed
and
the
plug
is
drawn
out.
Shorting
bars
are
provided
in the
case
to
short
the
current-transformer
circuits
16