ARMY T M    5 - 6 1 1 5 - 6 1 2 - 3 4 MARINE  CORPS   TM   6115-34/8 AIR  FORCE TO    35C2-3-471-2 NAVY AG-320B0-MME-000 1 0 - 1. PURPOSE   AND   FUNCTION   OF   ENGINE AND   GENERATOR   CONTROLS   AND INSTRU- MENTS.  (cont) Functional  Theory   of 0peration. (cont) b. transformer, an ac voltage is induced at the transformer output and applied to  rectifier/filter  circuitry. After rectification of the ac, it is filtered to supply both +12 Vdc and -12 Vdc levels to EECM circuits and also fed back to the control circuitry. If the voltage level on the +5 Vdc output line increases above about 6.2 volts, the crowbar control line passes this voltage to the crowbar control cir- cuit. In response,    the  crowbar  trips, shorting the prime input lines to- gether. The resulting short across the +24 Vdc prime power line causes the control panel circuit breaker to trip and  remove  power  from  the  generator  set. (2) Initial power application. Refer to FO-9, sheet 2. The DC CIRCUIT BREAKER on the control panel controls application of +24 volt battery power from the battery to the control panel and the EECM. Input prime power from the battery enters the control panel through TB1, passes through the CIRCUIT BREAKER  (when  closed),  and  is  dis- tributed on the panel. When the PANEL LIGHTS switch is closed, the two panel illumination lamps receive the +24 Vdc and  are  lighted.  Prime  power  is  also placed on the center pole of the MASTER SWITCH and CONTACTOR switch. Addition- ally, it passes through the battery line to the EECM where it is connected to the center pole of one set of relay contacts. To apply power to the EECM circuits, the operator places the MASTER SWITCH in the RUN position. This places power on    the +24 Vdc line from the control panel to the EECM. In the EECM, this voltage is distributed to various EECM circuits is also applied to the power supply circuit card. This supply in turn generates +5 Vdc and ~12 Vdc levels to power EECM logic and the microprocessor as ex- plained in paragraph 10-1b(1) above. The  microprocessor    on    the  micro- processor circuit card is the control- ling and decision-making device for the entire  engine and  generator controls and  instruments. Stored within it is the software program that controls exactly how and in what sequence events are to happen that lead up to engine start and contactor enable. It also monitors various status lines  to determine if faults have occurred, and makes decisions as to whether or not the generator set should be shut down -. if the fault occurs. When  the  micro- processor receives operating power on the +5 Vdc line from the power supply card, it enters a startup sequence that eventually leads to engine ignition and startup. The first step in the startup sequence sets the fault output from the microprocessor. This level is buffered and sent to the switch circuit card where it is applied to a relay driver and a set of eight latches. In the latches, the fault level causes any latch input to be routed directly to a corresponding latch output without being altered. The microprocessor begins to monitor the speed signal from the monopole speed sensor signal from the exhaust gas temperature (EGT) thermocouple. The  speed  signal consists of a series of pulses from the monopole speed sensor such that more pulses are received when the engine is turning faster and vice versa. Any pulses on the speed signal line are clipped by the digital-to-TTL shifter so  that  output  pulse  levels from  the shifter are compatible with TTL logic levels required by the microprocessor. 1 0 - 2