Electric Governor Control Box Frequency Adjust Rheostat (MEP115A)

TM-5-6115-545-12 Power Unit Utility Pack Gas Turbine Engine Driven (Air Research Model PPU85-5) Non-Winterized and (Air Research Model PPU85-4) Winterized Manual
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T M 5 - 6 1 1 5 - 5 4 5 - 12 T O - 3 5 C 2 - 3 - 4 4 4 - 1 N A V F A C P - 8 - 6 2 6 - 1 2 T M - 0 0 0 3 8 G - 1 2 3 - 1 4 6 . 1 E l e c t r i c G o v e r n o r C o n t r o l B o x F r e q u e n cy A d j u s t R h e o s t a t ( M E P 1 1 5 A ) . g. The frequency adjust rheostat ( 1 , F i g 3 - 2 4 . 2 ) will adjust the oscillator frequency of the control box (2). The control box compares the oscillator frequency with the signal frequency sent from the magnetic pick up speed sensor (3). This sends the proper voltage to the electric governor actuator (4) which controls the speed of the engine. NOTE Normally this rheostat is only adjusted when the control box is changed or when there is a requirement to change the frequency of the governor set. ~. If the frequency of the generator fluctuates or is incorrect and cannot be adjusted by the Frequency Adjust ( 2 9 , F i g 2 - 1 0 ) control located on the generator set control panel, do not adjust the rheostat on the Electric Governor Control Box until the following checks are made: (1) Frequency Adjust ( 2 9 , F i g 2 - 1 0 ) on generator set control panel is in mid-position. (2) The magnetic pickup speed sensor is checked by removing its connector plug and sensor ( 3 , F i g 3 - 2 4 . 2 ) . Ensure there is no dirt or magnetic particles on the sensor’s end. To install the sensor, turn slightly by hand until the tip contacts the top of the Ring Gear Tooth (5). Then back out three- quarters of a turn and secure with jam nut (6). Reconnect wiring on the magnetic pickup speed sensor (3). WARNING Ensure DC power source is disconnected before the following step is accomplished. Serious injury could result if this procedure is not followed. (3) Remove connector plug (P22) from J-22 (7) and using a multimeter the following checks should be made: on P22; pin “G” to ground should be O ohms; pin “B” to “D” 8 ohms; pins “T” to “S” should read between 50 to 500 ohms; pins “F” to “R 500 ohms; pins “R” to “K” 2,000 ohms and pins “J” to “H” should read 85,000 ohms. Reconnect the battery, DC Control Circuit Breaker ( 2 0 , F i g 2 - 1 0 ) pushed in and the Start, Run, Stop Switch ( 3 2 , F i g 2 - 1 0 ) placed in the Run position. Connect the Multimeter between pin “C” and ground. A reading of 24 VDC should be obtained. Disconnect DC power source and connect plug (P22) to J22 (7, Fig 3-24.2); (4) Check for loose and/or binding electric governor actuator linkage. CAUTION The Frequency Adjust Rheostat (1, Fig 3-24.2) is a multi turn rheostat and will not handle excessive twisting and turning, otherwise damage to the rheostat will result. Adjust with care. (5) If the generator frequency is either high of low with the Frequency Adjust ( 2 9 , F i g 2 - 1 0 ) control located on the generator set control panel in mid position, adjust the Frequency Adjust rheostat ( 1 , F i g 3 - 2 4 . 2 ) in small increments. Check the Frequency Meter (3, Fig 2-10) on the generator control panel after each increment. Adjust until the proper frequency is attained. (6) If you cannot get the correct frequency after completing all of the above checks, notify higher level of maintenance for troubleshooting and repair. C h a n g e 1 5 3 - 7 2 . 1

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