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269Plus Motor Management Relay GE Power Management
THERMAL MEMORY 3 SETUP AND USE
3
c) LEARNED COOLING TIMES
Through various measurement and averaging techniques the 269Plus "learns" a number of motor parameters.
All learned values can be examined in Actual Vales page 6. If RTDs are used to monitor the temperature of the
motor stator the relay will learn the running and stopped cooling times of the motor. In this way the 269Plus
provides increased accuracy in the thermal modeling of the protected motor. When RTD #10 is used for ambi-
ent air temperature monitoring even greater thermal protection is provided since the cooling air temperature is
known. In this case the learned cool times are based on the difference between the ambient temperature and
the average stator RTD temperature. When no ambient sensing is used the learned cool times are based only
on the average stator RTD temperature. If no stator RTDs are used, or if the
DEFEAT LEARNED COOL TIME
set-
point (Setpoints page 5) is left as
YES
, the relay will use the default stopped and running cool time setpoints.
The learned cooling times should not be enabled until the 269Plus has had sufficient time to learn the
actual motor cooling times. The time required will vary between motors, however several start/stop
cycles will be necessary.
The 269Plus learns the motor cooling times over various temperature ranges. Thus the times shown in page 6
of ACTUAL VALUES mode (
LEARNED RUNNING COOL TIME
,
LEARNED STOPPED COOL TIME
) will reflect the total
cooling time as a combination of the cooling times over each temperature range.
d) START INHIBIT
An OVERLOAD TRIP caused by the exhaustion of motor thermal capacity will cause a lock-out. A relay reset
is not allowed until the memory has discharged to 15% thermal capacity used. At this point the relay can be
reset.
If the Start Inhibit feature is enabled (Setpoints page 5), a motor start will not be allowed until the thermal mem-
ory has discharged sufficiently to make the start possible. The 269Plus uses the
LEARNED START CAPACITY
REQUIRED
(Actual Values page 6) to determine if a start is possible. If sufficient thermal capacity is available for
a start, the start will be successful. Thus the START INHIBIT lock-out time is adjusted to allow for optimum
motor usage. To override a START INHIBIT or OVERLOAD TRIP lock-out condition the Emergency Restart
feature can be used. If the Start Inhibit feature is disabled the OVERLOAD TRIP lock-out time will not be
adjusted by the learned starting capacity value and will represent the time for the thermal memory to discharge
to 15% thermal capacity used. Thus the lockout time will equal 85% of the STOPPED COOL TIME when Start
Inhibit is disabled. When Start Inhibit is enabled the OVERLOAD TRIP lock-out time will represent the time for
the thermal memory to discharge to the
LEARNED START CAPACITY REQUIRED
value.
Before the 269Plus learns the actual Start Capacity required by the motor, this value defaults to 40%.
The
LEARNED START CAPACITY REQUIRED
is the thermal capacity used and learned by the relay over the last five
starts. To ensure successful completion of the longest and most demanding starts, a safe margin between the
actual start capacity required and the learned value is built-in. This safety margin can be as high as 24%.
Every start is examined and its thermal capacity is captured and shown Actual Values page 6 as the
LEARNED
START CAPACITY, LAST START TC
. If the value learned is less than 10%, it is forced to 10% when it is used in cal-
culating the
LEARNED START CAPACITY REQUIRED
over the last 5 starts. It is forced to a maximum of 70% if the
TC learned for the last start is more than 70%. It is recommended that the "Start inhibit" feature should not be
enabled until the 269Plus has had sufficient time to learn the actual motor start thermal capacity under normal
operating conditions. The time required should include at least five start/stop cycles. To prevent the 269Plus
from learning bogus numbers when it is being tested, or upon commissioning, the relay should be placed in
"Test mode". This can be done on Setpoints page 6:
NOTE
PLACE 269 PLUS IN
TEST MODE? YES
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