Guardian 4389 Repair Manual page 28

SECTION 2.1
DESCRIPTION & COMPONENTS
INTRODUCTION
The air-cooled, pre-packaged automatic standby sys-
tem is an easy to install, fully enclosed and self-suffi-
cient electric power system. It is designed especially
for homeowners, but may be used in other applica-
tions as well. On occurrence of a utility power failure,
this high performance system will (a) crank and start
automatically, and (b) automatically transfer electrical
loads to generator AC output.
The generator revolving field (rotor) is driven by an
air-cooled engine at about 3600 rpm.
The generator may be used to supply electrical power
for the operation of 120 and/or 240 volts, 1phase, 60
Hz, AC loads.
A 2-pole, "V-Type", prepackaged transfer switch is
shipped with the unit (see Part 3). Prepackaged trans-
fer switches do not include an "intelligence circuit" of
their own. Instead, automatic startup, transfer, run-
ning, retransfer and shutdown operations are con-
trolled by a solid state circuit board in the generator
control panel.
ENGINE-GENERATOR DRIVE SYSTEM
The generator revolving field is driven by an air-
cooled, horizontal crankshaft engine. The generator is
BRUSH HOLDER
ASSEMBLY
Page 26
STATOR
ROTOR
REAR BEARING
CARRIER
Figure 1. AC Generator Exploded View
PART 2
directly coupled to the engine crankshaft (see Figure
1), and mounted in an enclosure. Both the engine and
generator rotor are driven at approximately 3600 rpm,
to provide a 60 Hz AC output.
THE AC GENERATOR
Figure 1 shows the major components of the AC
generator.
ROTOR ASSEMBLY
The 2-pole rotor must be operated at 3600 rpm to
supply a 60 Hertz AC frequency. The term "2-pole"
means the rotor has a single north magnetic pole and
a single south magnetic pole. As the rotor rotates, its
lines of magnetic flux cut across the stator assembly
windings and a voltage is induced into the stator
windings. The rotor shaft mounts a positive (+) and a
negative (-) slip ring, with the positive (+) slip ring
nearest the rear bearing carrier. The rotor bearing is
pressed onto the end of the rotor shaft. The tapered
rotor shaft is mounted to a tapered crankshaft and is
held in place with a single through bolt.
ENGINE
ADAPTOR
AC GENERATORS
ENGINE