GE Multilin M60 Motor Protection System 5-151
5 SETTINGS 5.6 GROUPED ELEMENTS
5
–TCU
end
= TCU value dictated by the hot/cold curve ratio when the motor is running. This value is 0 when the motor
is stopped).
– t = time in minutes.
– = cool time constant (running or stopped per current motor status and corresponding
COOL TIME CONSTANT RUN-
NING and COOL TIME CONSTANT STOPPED settings).
– I
eq
= equivalent motor heating current
– overload_pickup = overload pickup setpoint as a multiple of FLA
– hot / cold = hot/cold curve ratio
Figure 5–59: THERMAL MODEL COOLING
• HOT/COLD SAFE STALL RATIO: The motor manufacturer will sometimes provide thermal limit information for a hot/
cold motor. The algorithm will use this data if this setting is programmed. The value entered for this setting dictates the
level at which thermal capacity used will settle for current that is below the motor service factor times FLA. When the
motor is running at a level that is below this limit thermal capacity used will rise or fall to a value based on I
equivalent
(average three phase RMS and the selected setting. Thermal capacity used will either rise at the fixed rate of 5% per
minute or fall as dictated by the running cool time constant.
(EQ 5.16)
808705A2.CDR
0
25
50
75
100
0 30 60 90 120 150 180
Time in Minutes
Thermal Capacity Used
Cool Time Constant= 15 min
TCused_start= 85%
Hot/Cold Ratio= 80%
Ieq/Overload Pickup= 100%
0
25
50
75
100
03060 90 120 150 180
Time in Minutes
Thermal Capacity Used
Cool Time Constant= 15 min
TCused_start= 85%
Hot/Cold Ratio= 80%
Ieq/Overload Pickup= 80%
0
25
50
75
100
03060 90 120 150 180
Time in Minutes
Thermal C apacity Used
Cool Time Constant= 30 min
TCused_start= 85%
Hot/Cold Ratio= 80%
Motor Stopped after running Rated Load
TCused_end= 0%
0
25
50
75
100
03060 90 120 150 180
Time in Minutes
Thermal Capacity Used
Cool Time Constant= 30 min
TCused_start= 100%
Hot/Cold Ratio= 80%
Motor Overload
TCused_end= 0%
MOTOR TRIPPED
100% LOAD
MOTOR STOPPED
80% LOAD
TCU
end
I
eq
1
hot
cold
-----------
–
100%=
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