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I
.
L
.
41
-
668.1 E
ward bias diode D 3
.
This short circuits
capacitor
C
2
through Q
2 and
removes
the
charge
that had
started
to
build
up
.
Since the
charge
on
C
2 had
not
reached a level
to
fire
Q
3
,
the control
flip
-
flop
has
not
changed
state
,
the
reclosing
circuit remains
off
,
and the lockout indicator remains
on
.
The breaker
will remain locked
out
until
manually
closed
.
the short
-
circuit from
capacitor
C
2
allowing
it
to
charge through
RIO
and
potentiometer
R 37
to
the
firing voltage
of
unijunction
transistor
Q
3
.
The
time
required
for C 2
to
charge
and fire
Q
3 is controlled
by potentiometer
R 37
set to
a
calibrated time dial
.
When
Q
3 fires
,
C
2
discharges through Q
3 and R 12
to
cause a
voltage
rise
across
R 12
.
This
causes
the
voltage
on
the emitter of
Q
4
to
rise above its base
voltage turning
it off and
flip
-
flop
transistor
Q
5
on
.
When
Q
5
turns on
,
its
collector
voltage drops
to
a
low level and
removes
the base drive
to
Q
7
turning
it off
.
The low collector
voltage
of
Q
5 also disables
the
timing
circuit
by
forward
biasing
diode D 4 and
providing
a
path
for
current to
flow
through Q
5
so
that
capacitor
C
2
cannot
charge
up
to
a
point
where
it will
again
fire
unijunction Q
3
.
When the
turn
on
of
transistor
Q
5 turned
Q
7 off
,
the
potential
of the
col
-
lector
of
Q
7
rose
and
supplied
base drive
to
Q
8
turn
-
ing
it
on
.
The
turn on
of Q
8 allows base
current to
flow from
Q
9
turning
it
on .
This
switching
on
of
Q
9
energizes
the close
relay
,
closing
the
normally
open
contact to
the
positive battery supply
.
CHARACTERISTICS
Voltage Rating
The SGR
-
51 is rated for 48
or
125 volts d
-
c
.
Un -
less otherwise
specified ,
the
relays
are
connected
for 125 - volt
operation
when
shipped
.
Temperature Range
The SGR
-
51 is
designed
to
operate
over a tem
-
perature
range
from
—
20
#
C
to
+
55
*
C with
timing
vari
-
ations of
not more
than
+
5 %
.
Energy Requirements
If
a fault
appears
on
the
protected line
and
a
protective relay
opens the breaker
,
the 52 b
con
-
tacts
make up
providing
a
path
to
battery positive
through
the closed
contacts
of the close
relay
to
energize
and
immediately
reclose the breaker
.
55
milliamperes
at
rated
voltage
.
SETTINGS
Reset Time Setting
The
reclosing
of the breaker reopens the 52 b
contact
,
switching
transistors
Q
1 and
Q
6
on
.
Cap
-
acitor C
5 then
discharges through Q
6
to
give
a re
-
sultant
voltage drop
across
R 19 which
causes
the
voltage
on
the emitter of
Q
5
to
rise above its base
voltage
.
This
causes
flip
-
flop
transistor
Q
5
to turn
off
, setting
the
flip
-
flop
.
With
Q
5 turned off
, Q
7 is
supplied
with base drive
switching it
on
and
Q
8 and
Q
9
off
.
With transistor
Q
9 turned off
,
the close
relay
is de
-
energized
and its
contact
reopens
.
With the
turn
off of
Q
5 and the
setting
of
the
flip
-
flop
,
Q
4 is
turned
on
,
and the lockout indicator
circuit
is
ener
-
gized by Q
4
shorting
out
the
base drive
to
Q
10
,
turn
-
ing
it off
,
thereby switching Qll
on to
energize
the
amber lockout indicator
.
The
reset
time is
controlled
by
front
-
mounted
potentiometer
R 39 which has
a
calibrated time dial
.
The
reset
time is variable from 3
to
30 seconds
.
INSTALLATION
The
relays
should be mounted
on
switchboard
panels
or
their
equivalent
in
a location
free from
dirt
,
moisture
,
excessive vibration and heat
.
Mount
the
relay vertically by
means
of the four
mounting
holes
on
the
flange
for semi
-
flush
mounting
or
by
means
of the
rear
mounting
stud
or
studs for
pro
-
jection mounting
.
Either
a
mounting
stud
or
the
mounting
screws
may
be utilized for
grounding
the
relay
.
The electrical connections
may
be made di
-
rectly
to
the terminals
by
means
of
screws
for
steel
panel
mounting
or
to
the terminal studs furnished
with the
relay
for thick
panel mounting
.
The terminal
studs
may
be
easily
removed
or
inserted
by
locking
two nuts
on
the stud and then
turning
the
proper
nuts
with
a
wrench
.
See
Fig
.
8 for outline and
drilling plan
.
When the 52 b
contact
reopened and
switched
tran
-
sistor
Q
1
on
,
the base drive
to
Q
2
was
shorted and
Q
2 turned off
to reverse
bias diode D 3 and allow
capacitor
C
2 to
again charge through
R 37
and
RIO
.
Let
us assume
that
a
protective
relay
operates
to
trip
the breaker before
capacitor
C
2 has
charged
to
the
firing
level
of
Q
3
.
When the breaker
opens
,
the 52 b
contact
closes
switching Q
1 off and
Q
2
on to
for
-
For detailed FT
case
information
,
refer
to
I
.
L
.
41
-
076
.
3
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