T-45C TS, ADV & IUT ENG-27/ENG-28
Engineering Review
(3) Push-pull thermal circuit breakers of
various amperage levels provide
(a) Bus connection for aircraft electrical
systems
(b) Isolation/protection for their respective
functions in the event of electrical
failures
6.
Power distribution relays and contactors
Sg 5, fr 10
Relays
a.
Generator Fail and Inverter No. 2 Power Input
Relay removed and inverter No. 2 wired directly
to 28 VDC essential services bus on aircraft
165457 and up and on aircraft 165456 and
below with AFC 199 incorporated
b.
AC isolation relays disconnect non-essential
services 115 and 26 VAC buses from 115 and
26 VAC essential buses when generator goes
off-line
c.
Three contactors provide bus connection to
battery and external power
Sg 5, fr 11
Fig 1:
B. Electrical system operational characteristics
Electrical System
Block Diagram
1.
DC power system: consists of two batteries,
generator, voltage regulator, overvoltage unit, two
Sg 5, fr 12
28 VDC buses, and undervoltage unit
Generator
a.
Power generation
(1) Main electrical power supplied by 28 VDC
generator
(2) During ground starts the GEN caution light
Sg 5, fr 13
will extinguish when a suitable DC output is
Voltage Regulator
obtained 25-25.2 VDC (at approximately
42% RPM) the voltage regulator controls
output voltage to 28.2-29.2 VDC by
adjusting generator excitation voltage
Sg 5, fr 14
Overvoltage Unit
(3) Overvoltage protection unit monitors
generator output and prevents voltage from
exceeding 30.2 VDC by shutting down
generator
(9-98) Original
Page 27-10
Previous Page
