Electrical system Flashcards
If a CB trips, how many reset attempts are allowed?
1 reset attempt is allowed
How many types of Electrical Power Supply for we have?
28V DC (MAIN ELECTRICAL POWER)
2x 28VDC 400A Starter/Generators
2x 24VDC 43Ah Ni-Cad Batteries
1x 28VDC External Power Supply
EMERGENCY POWER SUPPLY
1x 24VDC 5Ah Battery comprised of
rechargeable D cells
115V/26VAC
2x single phase 400Hz Inverters
115/200 VAC ‘Wild’
2 x 3 phase 115VAC Generator 460 – 600Hz
(for Ice protection and galley mug ONLY)
2 x 24VDC 43Ah Ni-Cad BATTERIES
installed outside the pressure hull
fitted with thermal protection sensors
1 hour discharge rate (refer E17)
No Batt start
57 - 71 degrees
No CWP light
Hot Batt
Above 71 degrees
should the Generator temperature reach 150ºc
GEN OV TEMP light on the overhead panel will illuminate, along with a CWP
the Generator is NOT Automatically taken off line
External power
EXTERNAL POWER ALWAYS HAS PRIORITY OVER THE BATTERY AND THE GENERATOR RELAYS
1 x 24VDC 5Ah BATTERY
(EMERGENCY POWER SUPPLY)
Location and how does it work?
- located in the Avionics Rack
- 1 hour duration of power
- has its own integral heater (temp kept
between 27ºC and 55ºC) - when the L BAT Bus is powered, the
EMERGENCY BATTERY is charged from this bus - requires a Battery Switch to be ON to
power Emergency Bus - supplies power to the Emergency Bus,
when the L Bat Bus voltage drops below
24 VDC (provided a Battery Switch is ON)
An EMER POWER light on the overhead panel will illuminate if:
- Emergency Battery voltage drops below 24 VDC
- Emergency Bus not powered
- Emergency Battery is not being charged
INVERTER light will illuminate if
the selected 115 VAC inverter fails, or the switch is set to OFF
the Inverters are protected against:
over/under voltage
over/under frequency
over temperature
2 x 115/200 VAC ‘WILD’ GENERATORS
driven from the Propeller Gear Boxes
for Ice protection ONLY
GENERATOR CONTROL UNITS:
provide both control and protection for the
starter/generator, in both start and generate modes
Start Mode:
energises the start relay
disables GCU control functions
starter cut out at 55% Ng
at 55% Ng, the starter “CUTS OUT” and the
STARTER /GENERATOR becomes a GENERATOR
GCU will de energize a generator relay
- over voltage (>40VDC)
- short circuit
- reverse currents
- Fire Handle pulled
BUS TIE RELAY
IN ORDER TO ENERGIZE THE BUS TIE RELAY:
- THE LEFT BATTERY SWITCH MUST AT SOME TIME HAVE BEEN TURNED ON
when the Bus Tie Relay is energized, it connects the L GEN BUS to the R GEN BUS (it ties the 2 sides together)
This allows:
- External Power to energize ALL buses
when it is switched on
- to enable ONE Generator to energize
ALL buses (exception: Utility Bus) - to connect the 2 Batteries
- the Bus Tie Relay is protected against short circuiting, by a Bus Tie Overcurrent Relay
- If the current from 1 Gen Bus to another exceeds 800A, the Bus Tie Relay is de-energized
- it can be reset via cb K1
- During a start, the amperage across the Bus TieRelay can be as much as 1600A
so the Bus Tie Overcurrent Relay is inhibited during an engine start
BUSES THAT ARE ENERGIZED WITH BATTERIES ONLY
- L/R HOT BATTERY BUSES
- L/R BATTERY BUSES
- L/R GENERATOR BUSES
- L/R ESSENTIAL BUSES
- EMERGENCY BUS
(Essential Avionics Switch ‘ON’ also)
- ESSENTIAL AVIONICS BUS
- EMERGENCY AVIONICS BUS
When starting the engine on battery power
L/R ESS busses are taken offline
When starting the engine with ground power
L/R ESS bus are taken offline
L/R ESS main smart bus are online
After start Electrical sequence
- Both generators are running
- Left engine powers L and Right powers R
- Generators are the source of power and keep the battery charged
- ## The Bus tie is NOT connected
When will the EMER PWR overhead panel light illuminate?
Emergency Bus is not powered, or
Emergency Battery Voltage drops below
24 VDC
At what temperature will the BAT HOT light
illuminate, and will the Battery Relay be
deenergized (open)?
71ºc, yes
How are the Batteries cooled?
fan on the ground, ram air when airborne
What is indicated by illumination of L/R MAIN BUS light?
associated bus is not powered
