ARMY *TM 9-6115-464-34 AIR FORCE TO-35C2-3 ... - Igor Chudov

ARMY TM 9-6115-464-34AIR FORCE 35C2-3-445-2NAVY NAVFAC P-8-624-343-65. ELECTRIC GOVERNOR CONTROL UNIT (MEP-113A).a. General.(1) The electric governing system is a speed (frequency) sensing system used to maintain constantengine speed and generator output frequency during periods of unchanging load and when loadadditions or deletions occur. The system consists of a control unit, magnetic pickup and an electricthrottle actuating unit. The engine speed signal is obtained from a magnetic pickup mounted in theflywheel housing in close proximity to the flywheel ring gear. The frequency of the pickup signal isproportional to engine speed. Figure 3-85 shows the functional theory of operation.(2) The control unit has four distinct circuits: pickup signal amplifier, frequency reference oscillator,phase comparator and output circuit.(a)(b)(c)b. Malfunction.The frequency reference oscillator is voltage controlled. The frequency setting is adjusted byapplying zero to 10 volts at the frequency reference oscillator input. The internal frequency adjustprovides this voltage setting when the control unit is in operation. The reference oscillator does notmaintain a constant frequency. It deviates from its nominal frequency as the engine speed changesduring load changes. The reference oscillator is forced by the phase comparator to track theamplified pickup signal representing engine speed. The voltage representing speed error is theamount of voltage required to drive the reference oscillator off frequency in proportion to the enginespeed deviation.The phase comparator circuit receives signals from the pickup signal amplifier and the referencefrequency oscillator and compares the difference in frequency. The phase comparator measuresthe amount the engine signal is ahead or behind the reference oscillator signal. Its voltage output isused to force the reference oscillator to the same frequency as the signal from the engine. Thephase comparator output is proportional to the speed error. The gain control is used to couple thephase comparator output to the reference oscillator. By increasing the coupling, a small voltagechange from the phase comparator represents a large frequency change and vice-versa.The output circuit allows governing by introducing a temporary drop during a load change forstability purposes. It has an adjustable means to control the magnitude and time constant of thedrop to match the dynamic characteristics of the engine. The output current switching portion of thecircuit provides current to drive the actuator. The output transistor is switched on and off at afrequency of 200 Hz. This is above the natural frequency of the actuator. The actuator responds tothe average current from the transistor and moves in proportion to position the engine throttle. Theoutput transistor is switched on and off to reduce power dissipation.The following procedures are to be performed with the governor control unit in the generator set.(1) Connect the breakout cable (7, figure 3-86) as follows: Disconnect P17 (6) from J17(1), connectP17A(7) to J17(1), connect J17A(7) to P17(6).(2) Using a digital voltmeter, make the voltage readings in table 3-7 at the breakout cable plug. Allreadings are measured between the terminal and ground. Terminals F, G, H and T are ground.c. Removal.(1) Disconnect electrical connector P17 (1, figure 3-86).(2) Remove 4 hex head screws (2), Iockwashers (3) and nuts (4).(3) Remove the governor control unit (5).d. Installation(1) Position governor control unit (5, figure 3-86).3-186