ATA 24 Electrical Systems Flashcards
The BUS TIE relay will open when?
1) The AMC detects a different current value between the main BUSES
2) The Main Voltage drops below 12V
3) GEN1 or GEN2’s current difference is more than 75A
The BUS TIE relay will close when?
1) BATT MASTR switch to ENGAGE
2) BUS TIE SWITCH ON
3) Switch engine ON
With 2 Generators on, which BUSes are live?
ALL BUSES
With 1 generator offline, what BUS is offline?
The NON-ESS BUS
With 2 Generators offline, what BUS is offline
SHED BUS & NON-ESS BUS
The battery box contains what?
BAT HOT BUS, BR, EPR and BAT BUSS
The BAT BUS is connected to what?
The DIODE BOX 1&2 and the BUS TIE relays
The ESS BUS & AMC BUS take power from where?
The BAT BUS through the DIODE BOX
DIODE BOX 1&2 have power coming in from where?
The BAT BUS and MAIN BUS 1&2
Where are the BUS TIE’s located?
In the DISTRIBUTION BOXES
The EMERGENCY BATTERY is charged from where?
All 3 sources - The MAIN BAT, GENERATORS or EPU
Who has command, the BATTERY or the EPU?
The EPU through the control box.
The electrical system operates at what Voltage?
28.5V
The electrical system is designed to what principle?
A Duplex Parallel generation and seperation system.
What Voltage supply is the battery?
24V
If both generators and the main battery fail, what supplies the power?
The emergency battery to the emergency equipment.
What is acting as the return conductor for some electrical sub-systems?
The airframe
The electrical supply system consists of how many systems?
Four.
➢ Starter/generator system
➢Battery system
➢Emergency power supply system
➢External power supply system
Where are the AMC’s installed?
in the avionic bay below the cockpit floor
What WARNINGS can you have on the electrical system?
BATT OVERTEMP only
What is the BATT overtemp trigger?
71C inside the battery casing.
What is responsible for the power generation control and protection circuits?
The Generator Control Units (GCU)
What are the current sesnors connected to?
GCU’s & AMC’s to measure current from the generators, battery and EPU
What RPM do the starter windings de-energise?
61% N1
How many brushes are in the generator?
Four
What output do the generators produce?
200A by 26-30V
Where is the TEMP SWITCH located for the generators?
On the mounting flange
What controls the starter gen relays?
The GCU
How is the GCU powered?
by the respective GEN or, backup power is via the ESS BUS
What voltage is an OVERVOLTAGE from the GEN?
exceeding 31.5V
What is an UNDERVOLTAGE?
below 20V
What is an OVERCURRENT?
230A
What is a REVERSE CURRENT?
a reverse current in the circuit.
What is a FEEDER FAULT?
when the current difference between two current sensors (CS1&CS2) is higher than 110 +-11 A
What is an Anti-Cycle protection
allows the pilot only one resest of the generator if the fault stays.
How many protection functions do the GCU’s provide?
6
The point of regulation (POR) setting is set by what?
pin-coding at the GCU connector
How does the GCU regulate the POR voltage?
by Pulse Width Modulation (PWM)
What ARINC does the HELIONX use?
ARINC 429
The GEN switches have how many positions?
- OFF, NORM, RESET
What does the GEN RESEST switch do?
Resest the respective GCU to reactivate the generator
What is the capabilty of the generator relays?
400 A
The status of the electrical system is displayed and monitored by what?
The HELIONIX system.
What triggers a Low voltage warning?
21V
What triggers a Low voltage caution?
24V
What triggers a high voltage caution?
29.5V or higher
What triggers a high voltage warning?
31V or higher
Where can the BUS voltage be adjusted?
the settings and tuning page.
How much can the BUS voltage be adjusted by?
+-1.9V
Where is the current for each generator measured?
Current Sensor 1 (CS1)
What is a high current caution?
200A
When will a high current caution turn into a warning?
after 2minutes above 200A, or 5s above 300A
What is a white generator symbol?
OFF / NOT CONNECTED
What is a green generator symbol?
ON / CONNECTED
What is a amber generator symbol?
ABNORMAL CONDITION STATE
If the generators are online, what will the battery current be?
a minus figure as it’s charging.
What is GEN OVHT TEMP?
178C
Where is the GEN TEMP SENSOR located?
In the mounting flange for the generator, monitoring the temp at the air outlet
What is a GEN DISC SENSOR advisory?
if the continuity check of the discrete signal for GEN DISCONNECT fails during the power up test.
What does the battery backup relay do?
connects the battery to the BUS TIE and warning unit
What is the voltage & capacity of the battery?
24V & 40Ah (optional 44Ah)
Where is the battery temp switch?
Inside the battery housing
How long can the battery provide power in an emergency situation?
30 mins
What temp does the BATT OVHT trigger?
71C
How can the battery be charged?
By the generators only
The battery switch has how many positions?
Three. OFF, NORM, ENGAGE
What happens when the battery is switched to ON?
The battery backup relay energises, powers the battery bus which then sends power through the diode box to the ESS & AMC BUS.
What happens when the battery master switch is set to engage?
The BUS TIE RELAYS are engaged and the self-locking loop keeps the BUS TIES closed. The master battery switch springs back to ON.
If the battery is set to OFF with the generators egaged, will it charge?
No
Which has priorty, the EPU relay or battery?
EPU via the control relay
Where is the battery back up relay located?
R/H cable channel.
When does BATT DISCHARGING appear?
when battery current is above 5 A for 3 mins, or 5A & less than 24.5V
What current trigger ELEC OVERLIMIT caution?
above 125A
Which BUS is the EMERGENCY POWER SUPPLY charged from?
ESS BUS 2
What does the EMERGENCY BUS power?
the IESI and the emergency lights
What is the OUPUT Voltage of the STNDBY BATTERY?
24.5V
Which pin of the EPU activates the EP control relay?
The short pin.
What does the external power control relay do?
provides a ground signal to energize the external power relay or battery relay.
What is the function of the external power interlock relays?
to disconnect the generators during ground operation
Where is the EPU current measured?
The same hall-effect current sensor as for the main battery current
Where are all the BUS BARS located?
in the junction and distribution boxes, the service connector panels and
the overhead panel.
When would the self-locking loop be opened?
in the case of an abnormal condition, causing the BUS TIES to OPEN
What happens if the MAIN BUS short circuit protection detects voltage below 12 VDC?
The short circuit protection opens the self-locking circuit, causing the BUS TIE relays to open. The AMC can also trigger it if there’s a current difference or limit exceeded.
What are the lower priority electrical systems connected to?
The SHED BUS and NON-ESS BUS.
What load are the SHED BUSES consumers?
normal load
Non-ESS bus is for what consumers?
High load and maintenance equipment.
Where are the AMC buses located?
With the NON ESS bus in the service connector panel
