SF340 Electrical Systems

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  1. What are the power sources for the DC electrical system? 5-1
    • Batteries
    • External power
    • Generators
  2. What are the 4 separate parts of the electrical system? 5-1
    28V DC (main & emergency), 115/26V AC, “wild” frequency 115V AC
  3. What makes up the 28V DC electrical system? 5-1
    2 Main Batteries and 1 Emergency Battery, 2 Engine Generators, and External PWR
  4. How many Ni-Cad batteries does the Saab 340 have? 5-2
  5. What type of main batteries does the Saab 340 have? 5-2
    24 volt 43 Amp hour Ni-Cad batteries
  6. Where are the main batteries located? 5-2
    In the respective wing-fuselage fairing
  7. How are the batteries ventilated for cooling? 5-2
    By ram air in flight, and fans on the ground
  8. What bus is used for battery charging? 5-2
    Respective GEN bus with at least one generator online
  9. Which bus is the right battery connected to? 5-2
    Right GEN bus
  10. What powers the Emergency Bus? 5-3
    The L BAT BUS (batteries must be ON/OVRD) or the Emergency Battery
  11. When does the Emergency battery begin to power the EMER BUS? 5-3
    When the L Battery power is lost
  12. Where is the Emergency Battery located? 5-3
    Avionics rack
  13. What is the power source for the emergency power system? 5-3
    Powered from the 28V DC system or the emergency battery
  14. What is indicated by an illuminated NO BAT START light? 5-3
    Battery temp has reached 57ºC
  15. What is indicated by an illuminated BAT HOT light? 5-3
    Battery has reached 71ºC
  16. What is indicated by an illuminated EMER PWR light? 5-3
    Either the emergency bus is not supplied power or the battery had decreased below 24V
  17. What is the purpose of the Series/Parallel relay? 5-3
    During a battery start of the first engine the batteries are connected in series to produce 48 volts.
  18. What type of Battery is used for the Emergency battery? 5-3
    24 volt 5 amp hour lead acid battery
  19. What is indicated by an illuminated L/R BAT HOT light? 5-3
    Associated battery temp has reached 71ºC
  20. What other light(s) would be on when a BAT HOT light is illuminated? 5-3
    • BAT
    • ELEC↑ on CWP
  21. What automatically happens when a battery temp reaches 71ºC? 5-3
    BAT relay opens
  22. Can the battery supply power to the GEN bus with a BAT HOT? 5-3
    Yes, in an emergency the BAT switch can be set to OVRD
  23. What would cause the GPU to automatically disconnect? 5-4
    • Overvoltage (>31v)
    • Under voltage (<10v)
    • Voltage drops below 10 volts with start switch held to L or R
  24. What is the voltage limit during a start with the start switch held to start? 5-4
    Voltage may drop to 7 volts
  25. What is the amperage of the 28V GPU? 5-4
    1200-1600 amps
  26. What is the minimum voltage required to get the magnetic latch to close for GPU usage? 5-4
    10 volts
  27. What does the blue EXT PWR AVAIL light indicate? 5-5
    GPU is connected to the A/C and supplying at least 7 volts
  28. How many generators on each engine? 5-5&25
    2 (DC & AC)
  29. When is the starter/generator acting as a starter? 5-5
    During engine start when Ng is between 0-55%
  30. Are batteries being used for a cross generator start? 5-5
    Yes, the batteries assist the generator to achieve a faster cooler start
  31. When is the GEN relay automatically opened? 5-6
    • GCU detects a malfunction (except overheating)
    • External power is used
    • Fire handle has been pulled
  32. When is the Gen relay light expected to be on? 5-6
    • When the respective Gen switch is off
    • When external power is powering the A/C
    • When a Fire handle has been pulled
    • When engine Ng is less than 55%
    • With a failure of the Gen
  33. How many electrical buses does the Saab 340 have? 5-6&7
    27 (21 is incorrect)
  34. What minimum Ng is required to connect the starter/generator to the GEN BUS? 5-6
  35. What is indicated by an illuminated L/R GEN light? 5-6
    The respective Gen relay is open (gen offline)
  36. The starter/generators are rated at what voltage? 5-6
    28 volts
  37. An illuminated GEN OV TEMP light on the overhead panel indicates what? 5-6
    Generator is overheated (150º)
  38. Can the Generators be “online” with EXT PWR on? 5-6
    No, the relay automatically opens
  39. What 3 conditions must be met for the GEN relay to close? 5-6
    • EXT PWR must be off
    • Engine start complete
    • Gen field reset
  40. What is indicated by an illuminated L/R MAIN BUS light? 5-8
    The associated main bus is unpowered
  41. What is indicated by an illuminated L/R ESS BUS light? 5-9
    Associated bus is not powered
  42. What is the purpose of the Bus Tie relay? 5-9
    To connect the left and right busses to run off one power source
  43. What is indicated by an illuminated BUS TIE CONN light? 5-9
    The bus tie relay is closed
  44. What are three reasons the Bus Tie relay closes? 5-9
    • EXT PWR is on
    • Only one Generator is operating
    • Either the LEFT or BOTH Batteries are on
  45. What is the purpose of the bus tie over-current relay? 5-9
    To protect the Main Distribution system in case of a short
  46. Bus Tie relay opens if the over-current exceeds how many amps? 5-9
    800 amps
  47. Can the Bus Tie over-current be reset manually? 5-9
    Yes, through the K-1 reset button
  48. What is required to close the Utility Bus relay (RCCB)? 5-9
    EXT PWR on or both generators on
  49. What powers the Emergency Avionics Bus? 5-9
    The Emergency Bus, when the ESS AVION switch is on
  50. Where does the battery bus receive power from normally? 5-11
    Gen bus
  51. The left battery is connected to which bus? 5-11
    Start bus
  52. While on battery power alone what lights illuminate on the DC ELEC panel? 5-14
    • L/R GEN
    • L/R MAIN BUS
    • EMER PWR (If BUS is below 24V)
  53. With the GPU powering the A/C what lights illuminate on the DC ELEC panel? 5-15
    • White EXT PWR
    • L/R GEN
    • L/R BAT
  54. What is the power source for the 115/26V AC system? 5-22
    2 115/26V AC inverters powered by the DC system
  55. What is indicated by an illuminated INVERTER light? 5-22
    Inverter switch is set to OFF or associated 115 volt Inverter has failed
  56. With a Failure of the 26V output of the inverter what warnings are given? 5-22
    No CWP warning or cautions, but an RMI failure and VOR CDI failure will occur
  57. What is the power source for the “wild” frequency 115V AC system? 5-25
    2 engine driven AC generators
  58. What is the “wild” frequency 115V AC power used for? 5-25
    Ice protection
  59. Why is the AC GEN called the “wild” frequency? 5-25
    Frequency varies with prop RPM, (460Hz to 640Hz)
  60. Where is the “wild” frequency generator located? 5-25
    On the prop gear box
  61. What is the minimum prop RPM for an AC GEN to supply power? 5-25
    1000 RPM
  62. If prop RPM drops below 1000 RPM, how is the AC GEN reset? 5-25
    Automatically resets when prop RPM increases above 1000 RPM
  63. What does an illuminated AC GEN light indicate? 5-32
    Generator is off line
  64. What items can be powered by the Emergency battery? 5-41
    • Audio system backup power
    • Bus tie CONN
    • Engine Fire Warning
    • Tailpipe hot Detection
    • WEU Backup
    • Emergency voltage indication
    • Emergency Avionics Bus
    • Stepdown from 24V to 6V for lighting of: Magnetic Compass, OBS, Pressurization, Standby Altimeter, Standby Attitude Indicator, Standby Airspeed
  65. What items are on the EMER AVIONICS BUS? 5-41
    VHF COMM 1, Standby Attitude Indicator
  66. What 3 conditions must be met for a battery relay to close?
    • BAT switch on
    • EXT PWR off
    • Battery temp below 71ºC
  67. What cools the DC generator?
    Ram air in flight and fans on the ground
Card Set
SF340 Electrical Systems
Colgan Air Saab 340 Chapter 5 - Electrical
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