GE Multilin 489 Instruction Manual page 192

Note
5–82
Courtesy of NationalSwitchgear.com
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% voltage level, the trip time of 110% will be used (see the figure below).
GE Multilin
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900
800
700
600
500
400
300
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100
90
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9
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1
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FIGURE 5–20: 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.
489
VOLTAGE DEPENDENT
OVERLOAD PROTECTION CURVES
Custom Curve
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
3 4 5 6
MULTIPLES OF FULL LOAD AMPS
489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
CHAPTER 5: SETPOINTS
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808831A3.CDR