CHAPTER 7
POWER GENERATING SYSTEMS
INTRODUCTION
Electronic devices, controls, and outputs are
covered here. For in-depth details, refer to NEETS,
Power generating equipment is the mainstay of
Module 7.
aircraft maintenance. In general, mobile
SEMICONDUCTORS
power-generating systems are used for starting aircraft
a n d f o r s u p p l y i n g p ow e r d u r i n g m a i n t e n a n c e
A semiconductor is a device that ordinarily acts as
procedures.
an insulator, but under certain specific electrical
The systems described in this course are the
conditions, it will become conductive. Figure 7-1
NC-2A, NC-8A, NC-10C, and MMG-1A. These
shows the resistance values of basic material in the
systems often differ greatly.
three general groups used in electronics (conductors,
The NC-2A has two generators--one ac and one
semiconductors, and insulators).
dc.
Semiconductor Materials
The NC-8A has one dual-purpose generator that
produces ac and dc.
Silicon and germanium are the most common
types of materials used to make semiconductors. The
The NC-10C and MMG-1A have one generator
greater availability of silicon gives it an advantage over
that produces ac only.
germanium. Silicon is also electrically superior in
some respects.
In the case of the MMG-1A, the dc output is
derived from the ac input power that drives the motor
N-TYPE MATERIAL.--Generally, silicon and
generator. The input power is stepped down by a
germanium do not conduct electricity. But by a
transformer and rectified for dc output. The NC-10C
process called doping (which is to add selected
also uses ac power from its generator, and uses
impurities), the electrical properties of silicon and
transformers and a rectifier type power supply to
g e r m a n i u m a r e altered. Silicon is doped with
produce dc power.
phosphorus--germanium with arsenic or antimony.
Some basic electrical theory is presented in this
When a semiconductor is doped in this way, it is
course; however, to be prepared for advancement, you
called N material. Doping N material is the inser-
should review the Navy Electricity and Electronics
tion of additional negative charges.
Training Series (NEETS) modules for more detailed
P - T Y P E M AT E R I A L . -- W h e n s i l i c o n o r
coverage of the topics covered here.
g e r m a n i u m i s d o p e d w i t h b o r o n , c o n d u c t iv i t y
increases. Semiconductor material doped in this way is
WARNING
called P material. It is the insertion of positive charges.
Electrical equipment designed for aircraft
servicing can provide sufficient voltage to be
dangerous to human life.
LOW RESISTANCE
HIGH RESISTANCE
CONDUCTORS
SEMICONDUCTORS
INSULATORS
SOLID-STATE ELECTRONICS
LEARNING OBJECTIVE: Identify the
operating characteristics of solid-state
ASf07001
c o m p o n e n t s u s e d i n p ow e r- g e n e r a t i n g
Figure 7-1.--Resistance chart of common conductors,
semiconductors, and insulators.
equipment.
7-1