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ELECTRO-HYDRAULIC  GOVERNOR  CONTROL  UNIT.
Figure 3-67. Load Measuring Unit Test Circuit and Test Data Relationship

TM-9-6115-464-34 Generator Set Diesel Engine Driven Tactical Skid Mtd 15 Kw 3 Phase 4 Wire 120/208 and 240/416 Volts Manual
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(1) (2) (3) (4) (5) (6) If the FL-NL or NL - FL transient exceeds 1-1/2 percent of rated speed and/or does not reestablish stable engine operating conditions within one second, realign the control unit in accordance with paragraph 3-64j. Also follow this procedure if the engine speed hunts. If the set cannot be stabilized, check sockets A and B of plug P-21 (figure 3-97) for 24 Vdc (A is positive). If the engine speed increases to above nominal operating speed, check sockets A and B of P-17 (figure 3–97) for 120 Vac. If it is missing, troubleshoot the generator set wiring. Refer to schematic and troubleshooting diagram plates located on inside of left and right engine compartment doors (figure  3-97).  If  it  is  present,  check  the  resistance  of  the  frequency  adjusting  circuit  consisting  of  R4 (250 ohms) rheostat R1 frequency adjust (500 ohms) and R6 (250 ohms) fixed resistor. Measure the total circuit resistance across N and T of harness plug PI 7 (figure 3-97). The circuit resistance should be 1000 ohms (5 percent tolerance). After testing for correct total resistance, test the operation of the frequency adjust rheostat by connecting an ohmmeter across pins M and T and revolving the frequency adjust rheostat through its entire travel. The resistance should vary from 750 ohms to 250 ohms. Repeat this procedure using the ohmmeter across pins M and N of the harness plug. If the problem persists, check sockets A and B of plug P-21 (figure 3-97) for 24 Vdc (A is positive). If the engine speed remains below the nominal operating speed, adjust RI. If there is no improvement, check the resistance of the frequency adjust circuit. Disconnect P–17 and check the resistance of the frequency adjust circuit consisting of R4 (250 ohms) fixed resistor, RI frequency adjust rheostat (500 ohms) and R5 (250 ohms, 5 percent) fixed resistor. Measure the total circuit resistance across N and T of harness plug P-17. The circuit resistance should be 1000 ohms (5 percent tolerance). After testing for correct total resistance, test the operation of the frequency adjust potentiometer by connecting an ohmmeter across pins M and T and revolving the travel. The resistance should vary from 750 ohms to 250 ohms. Repeat this procedure using the ohmmeter across pins M and N of the harness plug. Disconnect actuator electrical connector before making this measurement. Push actuator piston all the way down and adjust engine speed with manual throttle. If this value resistance is measured, check sockets A and Bat plug P–21 for 24 Vdc (A is positive). If the set is operating at a constant load and voltage and during an eight–hour period the change in ambient temperature does not exceed 60°F, the set frequency should not drift beyond 1/2 of one percent of rated frequency. The above requirement assumes that the set temperatures were stabilized at the initial and final ambient temperatures. NOTE If the drift in paragraph (4) is excessive, realign the control unit following the procedure outlined in paragraph 3-64j. At constant ambient temperature, constant load, constant voltage and constant barometric pressure, the set frequency should remain within a bandwidth of 1 percent of rated frequency for a period of 4 hours. If this bandwidth has been exceeded, realign the control unit in accordance with paragraph 3-64j. If the preceding solutions to the specific problem do not resolve the problems, replace and repair the control unit, actuator (paragraph 3-43) or load measuring unit (paragraph 3–63) as required. c. Removal. (1) Tag and disconnect electrical connectors to governor control unit. (2) Remove nuts (1, figure 3-68), Iockwashers (2), nuts (3), Iockwashers (4) and bracket (5), threaded rod (6) and lift governor control unit from mounting bracket. 3-158 ARMY    TM    9-6115-464-34 AIR   FORCE   35C2-3-445-2 NAVY   NAVFAC   P-8-624-34







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