GE M60 Instruction Manual page 258

5.6 GROUPED ELEMENTS
where: TCU
TCU
start
TCU
end
t
τ
I
eq
overload_pickup = overload pickup setpoint as a multiple of FLA
hot / cold
100
75
50
25
0
0
5
100
75
50
25
0
0
• 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
(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.
5-120
= thermal capacity used
= TCU value caused by overload condition
= TCU value dictated by the hot/cold curve ratio when the motor is running
(= 0 when the motor is stopped)
= time in minutes
= Cool Time Constant (running or stopped)
= equivalent motor heating current
= hot/cold curve ratio
Cool Time Constant= 15 min
TCused_start= 85%
Hot/Cold Ratio= 80%
Ieq/Overload Pickup= 80%
30 60 90 120 150
Time in Minutes
80% LOAD
Cool Time Constant= 30 min
TCused_start= 85%
Hot/Cold Ratio= 80%
Motor Stopped after running Rated Load
TCused_end= 0%
30 60 90 120 150
Time in Minutes
MOTOR STOPPED
Figure 5–52: THERMAL MODEL COOLING
TCU I
=
end eq
M60 Motor Protection System
100
75
Cool Time Constant= 15 min
TCused_start= 85%
Hot/Cold Ratio= 80%
50
Ieq/Overload Pickup= 100%
25
0
180
0 30 60
100
75
Cool Time Constant= 30 min
TCused_start= 100%
Hot/Cold Ratio= 80%
Motor Overload
50
TCused_end= 0%
25
0
180 0 30 60
MOTOR TRIPPED
hot
 
× ---------- - ×
1 100%
–
 
cold
5 SETTINGS
90 120 150 180
Time in Minutes
100% LOAD
90 120 150 180
Time in Minutes
808705A2.CDR
GE Multilin
equivalent
(EQ 5.16)