Marathon Electric DVR 2000E+ - Generator under Frequency Alarm

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Marathon Electric (a division of RBC Manufacturing Corp.) reserves the right to change specications and this manual without notice.
Revised 06/2011
Generator Under Frequency Alarm
When generator frequency drops below the selected knee frequency set point, the voltage set point is automati-
callyadjustedbytheDVR
®
2000E+sothatgeneratorvoltagefollowstheselectedPU(perunit)V/Hzcurve.When
operating in an under frequency condition, the HMI will change from a PYN status to an alarm status with alarm
code f015. The Windows
®
communication software also displays this alarm condition. The knee frequency is ad-
justablefrom40.0to70.0Hertz(defaultof59.0Hz)andthebaseslopeofthePUV/Hzcurvemaybemodiedbya
Slope Multiplier from 1.00 to 3.00 (default of 2.00 PU) through the Windows
®
communication software. If generator
frequency drops below 25 Hz, the regulator will stop providing generator excitation and AC metering.
If generator frequency drops below a detectable level and generator speed is greater than 850 RPM, a short
circuit condition is assumed and the regulator will force current up to the Field Current Limit value (see Field
Current Limiting).
UnderfrequencyV/Hzslopeisdependentuponthekneefrequencyandtheslopemultiplier.Thebaseslopeis
defined according to the following (see Figure 3-2):
 •Forakneebetween40.0and50.0Hz,thebaseslopeis1/50(0.02)Vpu/Hz,
 •Forakneebetween50.1and60.0Hz,thebaseslopeis1/60(0.0167)Vpu/Hz,
 •Forakneebetween60.1and70.0Hz,thebaseslopeis1/70(0.0143)Vpu/Hz,
where Vpu = 1.0 at regulator voltage set point. The base slope is modified by the Slope Multiplier to achieve a
desired voltage roll-off characteristic. See Figure 3-3 for examples.
Figure3-2Volts/HertzSlopesvs.KneeFrequency