ARMY TM 9-6115-464-34AIR FORCE TO 35C2-445-2NAVY NAVFAC P-8-624-34(3) To determine the maximum voltage variation at constant load:(a) One-half the observed voltage bandwidth (B) is the plus or minus value of voltage deviation atconstant load.(b) Divide each of the values obtained in (a) by the rated voltage of the generator and multiply by 100to convert to percentage.(4) To determine the maximum overshoot and undershoot at each load step, and express this as apercentage of its rated voltage, proceed as follows:(a) From the meter recording charts, determine the maximum amount that the voltage trace goesbeyond the line (3) of the observed voltage band following the load change. See figure 4-1 forillustration of overshoot and undershoot.(b) Divide the result obtained in (a) by rated voltage (as given on the generator nameplate), thenmultiply by 100 to convert to percentage.CAUTIONDo not use the constant operating voltage at each load as the divisor in thecomputation. Use only the rated voltage of the generator. Failure to observe thiscaution could result in damage to the equipment.(5) To determine the time required to restore stable voltage conditions after each load change (recoverytime):(a) The prescribed steady state voltage bandwidth, extended to the point at which the voltage traceleaves the prescribed steady state band, shall be considered as the time at which the transientconditions begin. The point at which the voltage trace enters and remains within the prescribedband after a load change shall be considered as the point at which stabilization begins.(b) Measure the distance (in inches) on the chart from the point where the voltage trace leaves theprescribed steady state band to the point where it re-enters and remains within the prescribedvoltage band for the next load condition.(c) Divide this distance by the chart speed (in inches per second). This will give the voltage recoverytime, in seconds.(6) Determine the voltage regulation for all load changes (e. g. rated load to no load, 1/2 rated load to noload to 1/4 load, etc.) as follows:(a) Using the indicating voltmeter readings subtract the load value of voltage from the no load value foreach load change (e. g. step (a) to step (b)). (For voltage regulators utilizing single-phase voltagesensing, the value of voltage in the sensed phase only shall be used in the above calculations. Forvoltage regulators utilizing multi-phase voltage sensing the average value of the sensed voltageshall be used.)4-13
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