What powers the IIDS?
- DC Ess Bus and
- # 2 DC Primary Bus
Protected by 9 CBs
What powers the EFIS?
- Left (#1) powered by #2 Primary Bus
- Right (#2) powered by DC Ess bus
What powers the DECU?
- DC Ess Bus when N1 < 60%
- Its own alternator when N1 > 60%
What energizes the two inverters?
- # 1 energized by #2 DC Primary Bus
- # 2 energized by DC Ess Bus
What do the two inverters power?
- # 1 and #2 single phase AC 115v at 400 Hz / 250 VA primary busses
- # 1 and #2 AC 26v at 400 Hz / 150 VA busses via step-down transformers
What are the specs for the AC generator?
- 3-phase 115v 400Hz
- 385 Hz @ 92% Nr
What powers the AC generator and what is it used for?
- Optional heated windshield
- Back-up when both DC inverters fail
- Back-up power for linear and rotary actuators
Goes offline when when one engine fails to reduce load on remaining engine
What is the device that converts AC to DC called?
Rectifier
What happens to the AC generator when an engine fails?
Goes offline to reduce load on remaining engine
What is the primary electrical system?
28v DC
What are the four sources of DC power?
- 2 x engine mounted 28V 200A starter generators (“shunt” motors)
- External power
- 24v 40Ah NiCad or Lead Acid battery
What do the #1 and #2 DC starter generators power?
- # 1 powers #1 DC Primary Bus, DC Ess Bus, and battery
- # 2 powers #2 DC Primary Bus
At what % N1 does the DC starter become a generator?
48%
What creates the highest electrical load in the aircraft?
A/C @ 90 Ah. Everything else is 65 Ah
What does the aircraft’s external power connect to?
- # 1 and #2 DC Primary Bus
- DC Ess Bus
It does not connect to the battery bus
What is the 24v 40Ah NiCad or Lead Acid battery connected to?
DC Ess Bus
At what temperatures does the 24v battery connect / disconnect?
- Disconnects from everything but batt bus when >= 63°C
- Reconnects when < 52°C
What does the Generator Control Unit (GCU) do?
- Ensures correct voltage and polarity
- Commands “DC GEN” contactor to connect to bus system
How many GCUs are there?
3: 2 DC and 1 AC
In case of a single inverter failure, what is the back-up?
Other inverter
In case both inverters fail, what is the back-up?
AC generator
Where is the electrical compartment located on the aircraft?
In the tail. Busses are in junction boxes.
What does the Bus Tie Circuit do?
- Enables battery to be charged by #1 DC Primary Bus
- Allows for isolation of battery to only power DC Ess Bus
- Disconnects battery from Primary Bus in case of dual generator failure
What happens in case of an Essential Bus Recovery (“ESS BUS V LOW”)?
- System isolates #1 DC GEN from DC Ess Bus
- Connects #2 DC GEN to DC Ess Bus
