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C-12 ELECTRICAL CW3 RIESE 18 APRIL 2003

C-12 ELECTRICAL CW3 RIESE 18 APRIL 2003. DC SYSTEM. -24V, 34 AMP HOUR NICKEL CAD BATTERY -2 250A 30V DC STARTER/GENERATORS -AN EXTERNAL DC POWER SYSTEM -These power sources supply the dual-fed system that distributes power to the aircraft through circuit breakers.

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C-12 ELECTRICAL CW3 RIESE 18 APRIL 2003

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  1. C-12 ELECTRICALCW3 RIESE 18 APRIL 2003

  2. DC SYSTEM -24V, 34 AMP HOUR NICKEL CAD BATTERY -2 250A 30V DC STARTER/GENERATORS -AN EXTERNAL DC POWER SYSTEM -These power sources supply the dual-fed system that distributes power to the aircraft through circuit breakers. -Battery powers starting and emergency operation of essential equipment powered from the Hot battery bus. -Main battery bus feeds the isolation bus that, in turn provides power to the left and right generator buses. Once the generator buses are powered, the 4 dual fed buses are powered.

  3. f • -For nicad batteries, a battery charge current detector monitors • charging rate. If the rate exceeds 7 amps for 6 seconds the • battery charge light comes on. • GENERATORS • Function as starters during start up, once running the • generators provide DC power to the a/c. • Reverse current protection prevents the generators from • absorbing power from the generator buses if the generators are not • operating, or if generator voltage is less than bus voltage.

  4. VOLTAGE REGULATION • -Generator control units(GCU) and line contractor relays regulate • voltage to provide: • - voltage regulation • - line contractor relay control • - generator load paralleling • - differential voltage and reverse current sensing and control • - overvoltage and overexcitation control • - start.generator priority • Once generator is on, the GCU compares the bus voltages to generator • output voltage. When these are nearly the same, the GCU closes the • contactor relay. Generator is then connected to the generator bus. With • both on line, the GCU equalizer relay energizes to enable load • paralleling circuits.

  5. VOLTAGE REGULATION CONT. • Both GCUs compare their respective generators output voltage • to the opposite generator. The GCUs then adjusts generator output • voltage so both generators equally share the load within appox 10% • If a generator develops a reverse current condition, the GCU opens • the line contactor relay to remove the generator from it generator bus. • Once this condition is cleared the GCU automatically resets and the • generator comes back on-line. • If output reaches 32v the GCU will de-energize the generator and trip • the line contactor. Once the condition clears, the generator must be • manually brought back on-line.

  6. EXTERNAL POWER • An appropriately rated GPU can supply power. GPU should be • capable of delivering 1100A starting and provide a continuous • load of 400A at 30V DC. With the external power connected • the generators will not come on-line. • DC POWER DISTRIBUTION includes: • Hot battery bus • Main battery bus • Isolation bus • left and right generator buses • Nos 1,2,3, and 4 Dual-fed buses • Nos. 1 and 2 Avionics buses • Optional No 3 avionics bus

  7. POWER DIST CONT • Battery directly powers Hot battery bus(always powered) • With battery on, the battery connects to the Main battery • bus. • The primary load of the Main Battery bus is the left and right • starter/generators during engine start. • Isolation bus serves as a connection between the left and right • generator buses. High amperage current limiters between the • isolation bus and the generator buses isolate the battery from • a generator bus fault. • 4 dual fed buses receive power simultaneously from the left • and right generator buses. These are always powered from 3 sources: • both generators and battery.

  8. AC POWER • 2 750VA, 400 Hz static invertors supply 115V and 26V AC power. • Left and right generator buses power the respective invertors. QUESTIONS??????

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