Motor Protection Relay Product Manual
PROTECTION
Overload
protection,
locked
rotor
protection,
and
repeat
start
protection
are
accomplished
by
a
scien-
tific
calculation
performed
by the
relay,
simulating
real-world
temperatures
.
The
temperature
simulation
protection
method
calculates
the
rotor
and
stator
heat
rise
based
on
measured
line
currents,
the
motor
thermal
heating time
constant,
and
the
motor
cooling
time
con-
stant
.
These
values
are
constantly
monitored
by
the
relay
andcompared
to
the set
trip
points
.
This
method
offers
complete
protection
for
all
motor
applications
.
If
RTD's
are
present
in
the
motor
the
auto-learning
function
will
allow the
relay
to
read
the
actual
heating
and
cooling time
constant
of
any
type
of
motor,
eliminating
the
need
for
programming
the
heating
and
cooling time
constants
by
an
operator
.
Starting
currents
and
acceleration
time
may
also
be
calculated
by
the
relay
in
auto-learning
mode
.
Ambient
-
(temperature)
START
Time
t