Generac 86640 - Manual (Page 16)

Section 1.4- INTRODUCTION TO TROUBLESHOOTING
Introduction
A revolving field RV/IM type generator does not have a
large number of parts. However, the parts are expensive. For
that reason, a 'parts replacement' method of troubleshooting
Is not cost effective. A basic understanding of generators is
required if one Is to achieve effective troubleshooting and
repair. The technician must understand why generators be­
have or don’t behave as they should. This section is Intended
to introduce the service technician to some of the fundamen­
tals of troubleshooting generator problems.
DANGER: RV AND IM TYPE GENERATORS PRO­
DUCE EXTREMELY HIGH AND DANGEROUS
VOLTAGES. CONTACT WITH LIVE WIRES AND
TERMINALS MAY RESULT IN HAZARDOUS AND
POSSIBLY FATAL ELECTRICAL SHOCK. ONLY
PERSONNEL WHO HAVE BEEN TRAINED IN THE
SERVICING AND REPAIR OF RV/IM GENERA
TORS SHOULD ATTEMPT TO TROUBLESHOOT,
TEST OR REPAIR SUCH EQUIPMENT.
Tools and Equipment
The generator service technician should have a well
stocked tool box having a good selection of common hand
tools. Such a tool box should be equipped with wrenches in
both english and metric sizes. A selection of nut drivers
(english and metric) is also recommended. In addition to
common hand tools, the following specialized equipment
should be available;
1. Volt-Ohm-Milliammeter or VOM
a. An accurate VOM Is necessary fortesting, adjusting and
troubleshooting.
b. Simply having a VOM is not enough- the technician must
be familiar with electrical circuits, must be able to read
wiring diagrams and electrical schematics, and must be
able to use the VOM effectively.
C. An accurate digital type VOM is recommended.
2. Frequency Meter
a. Frequency meter reads alternating current (AC) fre­
quency, in HERTZ or CYCLES PER SECOND.
b. Generator AC output frequency must be known in order
to check and adjust engine-generator operating speed.
See "ROTOR ROTATIONAL SPEECt in this section.
3. Insulation Resistance Tester
a. See Section 1.3, ‘INSULATION RESISTANCE TESTS".
b. This tester will allow the user to test Rotor and Stator
Insulation for breakdown under an applied voltage.
4. Load Bank- will permit a known electrical load to be applied
to the generator, i.e., fortesting and adjustment of the gener­
ator under load.
Rotor Rotational Speed
The revolving field (Rotor) is directly connected to the
engine crankshaft and will rotate at the same speed as the
engine. Engine speed is held nearly constant by an engine
governor. Some generator models utilize a constant speed,
MECHANICAL governor; other models may be equipped with
an ELECTRONIC governor. See Part 7, "ENGINE SPEED
CONTROL SYST^Kr.
Generators may be equipped with either a 2-pole or a
4-pole Rotor. A 2-poie Rotor has a single North magnetic pole
and a single South magnetic pole. A 4-pole Rotor has two
North magnetic poles and two South magnetic poles. The
following apply to 2 and 4-pole Rotor assemblies:
Figure 24. A Typical Frequency Meter
Figure 25. Typical 2 and 4-Pole Rotors
A. 2-Pole B. 4-Pole
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