TM 9-6115-604-34NAVFAC P-8-633-34(4)Adjust a regulated phase voltage (line-to-neutral) to rated voltage.(5)Read and record the generator frequency, and all line to neutral voltages.(6)Compute the voltage unbalance (VU) for each voltage and frequency test using the following formula:V MAX-V MINVU (L-N)=X 100V RATEDd.Results. The maximum voltage unbalance in the three line-to-neutral voltages shall not exceed 1 percent of therated line to neutral voltage.12-22. REGULATOR RANGEa.General. The voltage adjust device, associated with the voltage regulator provided with the generator set, musthave an adjustment capable of varying the regulated voltage throughout the limits, and under the various loadconditions and temperature ranges without causing the voltage droop of the set to exceed specification limits.The voltage adjust device must also be capable of providing an operating voltage other than rated voltage forspecial types of equipment, and to compensate for external line drop.b.Apparatus. Instrumentation or measuring load conditions, ambient temperature, and the generator field (orexciter field) voltage and current shall be as illustrated in Figure 12-5.c.Procedure.(1)Preparation for test.(a)Connect the load and field instrumentation in accordance with Figure 12-5, for one voltage andfrequency.(2)Test(a)Start and operate the generator set. Allow the set to stabilize at rated load, rated voltage, and ratedfrequency (60 Hz). During this period record all instrument readings, including thermal instrumentation, at minimum Aintervals of 10 minutes. If necessary, adjustments to the load, voltage, and frequency may be made to maintain ratedload at rated voltage and frequency. Adjustments to the voltage and frequency shall be limited to those adjustmentsavailable to the operator: specifically, adjustments to the voltage or frequency adjust devices. When utilizing the droop-type speed control system as the prime speed control, the speed and droop portions of the control may be adjusted. Noother adjustments to the voltage and frequency control systems shall be made. Adjustments to the load, voltage, orfrequency controls shall be recorded on the data sheet at the time of adjustment. Stabilization shall be considered tohave occurred when four consecutive voltage and current readings of the generator (or exciter) field either remainunchanged, or have only minor variations about an equilibrium condition with no evident continued increase or decreasein value after the last adjustment to the load, voltage, or frequency has been made.(b)No further adjustments shall be made to any set control for the remainder of this test except thecontrol panel voltage adjust device.(c)Record all instrument readings.(d)Remove load.(e)Record all instrument readings (after transients have subsided).(f)Adjust the terminal voltage to the maximum specified value of 4575 V, line-to-line.(g)Record all instrument readings.CAUTIONAt voltages above rated values, the generator will be supplying less than rated current; atvoltages below rated values, the generator will be supplying greater than rated current. Toavoid damage to Instrumentatlon and load banks do not by-pass the voltage and currentprotection devices.12-28
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