CHAPTER 24
PAGE 4
MAINTENANCE MANUAL EXTRA 300/SC
PAGE DATE: 16. June 2008
24-30-00 DC-GENERATION
(Refer to Figure 0 of Chapter 91) Power for the electrical
system is provided by an alternator and/or the battery. The
alternator serves as the main component to power the
electrical system and charge the battery during normal
conditions. The battery is used for starting the engine and
powering the electrical system when alternator power is not
available (engine not running). The battery also powers the
electrical system in case of alternator failure.
A rocker type master switch is used for energizing the master
relay, which connects power to the electrical system.
The alternator’s magnetic field is provided by a series of
permanent magnets secured inside a cup-shaped housing. As
this magnetic housing rotates around a fixed wire core, the
result is alternating current. A rectifier-type regulator
converts the alternating current into direct current and varies
the output voltage of the alternator to meet the requirements
of the electrical system loads. An ammeter is installed into
the system to provide an indication of current flow from or
to the battery.
The negative side of the battery is connected to the aircraft
steel tube design (negative ground). This provides a ground
for the system through use of the steel tube design. The
positive side of the battery is connected to the coil of the
master relay. This relay remains in relaxed state until the
master switch is placed to the ON-position. Placing the
master switch in the ON-position provides a ground for the
master relay energizing this relay. With the master relay
energized, a circuit exists from the battery through an
ammeter to the bus bar.
The bus bar powers the electrical equipment and accessories
furnished on the aircraft. The energized master relay will
also allow power from the battery to the starter relay.
The alternator supplies power to the bus bar through the
10 amp alternator circuit breaker. With the alternator power
available, the battery will be charged from the bus bar. The
ammeter, which is in series with the battery and the bus bar
will indicate the current flow to the battery. When the battery
reaches a state of full charge, the ammeter will show an
indication near "0".
PAGE DATE: 29. May 2009
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