Multi-engine Power Distribution System Operation
1. Normal Operation – DC Power
#1 and #2 DC Hot Bus powered
#1 and #2 Batteries “ON”. Ensure #1 and #2 Battery lights are on
DC Ess Bus powered
Note: Shed OVRD switch will recover DC non-essential bus
2. Normal Operation – AC Power
#1 and #2 Batteries “ON”. Ensure #1 and #2 Battery lights are on
#1 and #2 Generators “ON”. Ensure #1 and #2 GEN lights are on
#1 Generator powers the #1 AC Bus, #1 AC Ess Bus, #1 AC Non Ess Bus, #1 TR
#2 Generator powers the #2 AC Bus, #2 AC Ess Bus, #2 AC Non Ess Bus
#1 TR powers the DC Ess Bus and the DC Non Ess Bus
Non Ess Busses are powered as long as both the #1 and #2 generators are operating
3. Auto-Transfer Operation - #1 Generator fail.
K1 and K6 de-energized
#1 and #2 AC Non Ess and DC Non Ess Busses de-energized through NO K1 and K6 relay
contacts
#1 GEN light OFF, #2 GEN light ON
#2 Generator powers the #2 AC Bus, #1 and #2 AC Ess Busses
#2 Generator powers the #2 TR through the NC contacts of K1. #2 TR powers DC Ess Bus
4. Auto-Transfer Operation - #2 Generator fail.
K2 and K7 de-energized
#1 and #2 AC Non Ess and DC Non Ess Busses de-energized through NO K2 and K7 relay
contacts
#1 GEN light ON, #2 GEN light OFF
#1 Generator powers the #1 AC Bus, #1 and #2 AC Ess Busses, #1 TR
#1 TR power the DC Ess Bus
5. Power Recovery of a #1 Failed Generator Using the APU.
#1 Generator switch “OFF”. Ensure #1 GEN light is out.
APU switch “ON”. Ensure APU light is on.
#1 Bus Tie switch “CONN”.
APU generator powers #1 AC Bus, #1 AC Ess Bus
#2 Generator powers #2 AC Bus, #2 AC Ess Bus, #2 TR. #2 TR powers DC Ess Bus
#1 and #2 AC systems isolated by open contacts of energized K4 and K7 and de-energized K5
Note: Shed OVRD switch will recover non-essential busses if required
6. Power Recovery of a #2 Failed Generator Using the APU.
#2 Generator switch “OFF”. Ensure #2 GEN light is out.
APU switch “ON”. Ensure APU light is on.
#2 Bus Tie switch “CONN”.
APU generator powers #2 AC Bus, #2 AC Ess Bus
#1 Generator powers #1 AC Bus, #1 AC Ess Bus, #1 TR. #1 TR powers DC Ess Bus
#1 and #2 AC systems isolated by open contacts of energized K5 and K6 and de-energized K4
Note: Shed OVRD switch will recover non-essential busses if required
7. APU Ground or Two Engine Out Power.
#1 and #2 Batteries “ON”. Ensure #1 and #2 Battery lights are on
#1 and #2 Generator switches “OFF”. Ensure #1 and #2 GEN lights are out.
APU switch “ON”. Ensure APU light is on.
#1 and #2 Bus Tie switch “CONN”.
APU generator powers #1 and #2 AC Bus, #1 and #2 AC Ess Bus, #2 TR.
#2 TR powers DC Ess Bus.
Note: Shed OVRD switch will recover non-essential busses if required
8. External Power.
#1 and #2 Batteries “ON”. Ensure #1 and #2 Battery lights are on
#1 and #2 Generator switches “OFF”. Ensure #1 and #2 GEN lights are out.
Connect External Power plug. Check that the EXT PWR READY light is on.
EXT PWR switch “ON”. EXT PWR READY light goes out, EXT PWR light comes on.
#1 and #2 Bus Tie switch “CONN”.
External Power provides power to #1 and #2 AC Bus, #1 and #2 AC Ess Bus, #2 TR.
#2 TR powers DC Ess Bus.
Note: Shed OVRD switch will recover non-essential busses if required
9. Emergency Generator Power Ground Test.
WARNING: Ensure ALL AC power is removed from the system prior to conducting this test.
#1 and #2 Generator switches “OFF”. Ensure #1 and #2 GEN lights are out.
APU Generator “OFF”. Ensure APU light is out.
Bus Tie switches “OFF”
Connect the External Power plug. Check that the EXT PWR READY light is on.
EXT PWR switch “ON”. EXT PWR READY light goes out, EXT PWR light comes on.
Emergency Generator GND TEST switch “ON”.
Check for 115 VAC at TP .
Emergency Generator provides power to #1 and #2 Ess Bus, Emergency TR.
Emergency TR powers DC Ess Bus.
Note: The Shed OVRD should not be activated when emergency power is used.