INSTRUCTION
MANUAL
-
MODEL
DLP
400-5-75
OA
24
5.9
SHORT
CIRCUIT
The
short
circuit
mode
is a
contactor
that
places
the
ammeter directly
across
the
Dynaload
input
for
short
circuit
current
tests;
all
three
ammeter
ranges
may
be
used
in
this
mode
.
If
the
contactor is
energized
when
a
very
large
capacitive
source or
large
battery is connected
to
the
input,
it
may
cause
the
contacts
to weld
together
due
to
the
instantaneous
current.
To
prevent
this
from
occurring,
the
DC
load should be
increased
to
maximum
current,
and
the
relay
then
energized
by
the
short
circuit button.
5.10
CURRENT
LIMIT/POWER
LIMIT
PROTECTION
The
voltage
proportional
to
load current
generated
across
SHI
is
applied
through
R7
to
the
base
of
Q3
.
The
voltage
reference
generated
by
zener
diode
VR8
is
reduced
by
divider
network
R15
and
R50
(current
limit
adjust)
and
applied
to
the
base
of
Q4
.
Accordingly,
Q4
will normally
conduct,
thereby
turning
on
Q2
and
permitting
it
to
drive
the
Dynaload.
When
the
load
current
reaches
the
current
limit
point,
Q3
conducts,
thereby turning
off
Q4,
which
turns
off
Q2,
restricting
the
drive
to
the
Dynaload
in
a
constant
current
regulating
characteristic.
It
should
be
noted
that
zener
diode
VR1
begins
to
conduct
when
the
input
voltage
is approximately 102V, and
accordingly,
R5, R6, and
R7
divider
network
comes
into play
[DLP400-5-75QA]
