GE Multilin 489 Instruction Manual page 196
Generator management relay
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Also See for Multilin 489:
- Instruction manual (306 pages) ,
- Communications manual (78 pages) ,
- Instruction manual (38 pages)
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5–86
Courtesy of NationalSwitchgear.com
generator is assumed to be running if current is measured or the generator is online). A
machine with a stopped rotor normally cools significantly slower than one with a turning
rotor. Machine cooling is calculated using the following formulae:
TC
(
TC
=
used
used_start
⎛
TC
=
⎝
used_end
where: TC
= thermal capacity used
used
TC
= TC
used_start
used
TC
= TC
value dictated by the hot/cold safe stall ratio when the
used_end
used
machine is running (= 0 when the machine is stopped)
t = time in minutes
τ = Cool Time Constant (running or stopped)
I
= equivalent heating current
eq
overload_pickup = overload pickup setpoint as a multiple of FLA
hot / cold = hot/cold safe stall ratio
100
75
Cool Time Constant= 15 min
TCused_start= 85%
Hot/Cold Ratio= 80%
50
Ieq/Overload Pickup= 80%
25
0
0
30
60
90
120
Time in Minutes
80% LOAD
100
75
Cool Time Constant= 30 min
TCused_start= 85%
Hot/Cold Ratio= 80%
Motor Stopped after running Rated Load
50
TCused_end= 0%
25
0
0
30
60
90
120
Time in Minutes
MOTOR STOPPED
FIGURE 5–23: Thermal Model Cooling
t τ ⁄
–
TC
) e
(
)
TC
–
+
used_end
I
hot
⎞ 1
⎛
⎞
eq
-----------------------------------------
--------- -
×
–
⎠
⎝
⎠
overload_pickup
cold
value caused by overload condition
100
75
50
25
0
150
180
0
30
100
75
50
25
0
150
180
0
30
489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
CHAPTER 5: SETPOINTS
(EQ 5.34)
used_end
100%
(EQ 5.35)
Cool Time Constant= 15 min
TCused_start= 85%
Hot/Cold Ratio= 80%
Ieq/Overload Pickup= 100%
60
90
120
150
180
Time in Minutes
100% LOAD
Cool Time Constant= 30 min
TCused_start= 100%
Hot/Cold Ratio= 80%
Motor Overload
TCused_end= 0%
60
90
120
150
180
Time in Minutes
MOTOR TRIPPED
808705A2.CDR
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