GE 489 Instruction Manual page 113

4 SETPOINTS
The 489 takes the information provided and create protection curves for any voltage between the minimum and 100%. For
values above the voltage in question, the 489 extrapolates the safe stall protection curve to 110% voltage. This current
level is calculated by taking the locked rotor current at 100% voltage and multiplying by 1.10. For trip times above the 110%
current level, the trip time of 110% will be used (see the figure below).
1000
900
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100
90
80
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10
9
8
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1
1
Figure 4–15: VOLTAGE DEPENDENT OVERLOAD PROTECTION CURVES
The safe stall curve is in reality a series of safe stall points for different voltages. For a given voltage, there can be
only one value of stall current, and therefore only one safe stall time.
NOTE
GE Multilin
GE Multilin
OVERLOAD PROTECTION CURVES
Custom Curve
2 3 4
MULTIPLES OF FULL LOAD AMPS
489 Generator Management Relay
4.10 S9 THERMAL MODEL
489
VOLTAGE DEPENDENT
Acceleration Intersect at 80%V
Acceleration Intersect at 100%V
Safe Stall Time at 80%V,
80%V Stall Current
Safe Stall Time at 100%V,
100%V Stall Current
Safe Stall Points
Extrapolated to 110%V
5 6 7
808831A3.CDR
4
8
4-63