Generac Power Systems 941-2 User manual

SERIES IMPACT 36 PLUS II
Models 940-2 & 941-2
SERVICE
MANUAL
Manual Part No. 0D9057
Printed in U.S.A Revision A - 07/15/03
P.O. Box 297 • Whitewater, WI • 53190
Phone: [phone] Fax: [phone]

SAFETY
Throughout this publication, "DANGER!" and "CAUTION!" blocks are used to alert the mechanic to special
instructions concerning a particular service or operation that might be hazardous if performed incorrectly or
carelessly. PAY CLOSE ATTENTION TO THEM.
DANGER! UNDER THIS HEADING WILL BE FOUND SPECIAL INSTRUCTIONS WHICH, IF NOT COM-
PLIED WITH, COULD RESULT IN PERSONAL INJURY OR DEATH.
CAUTION! Under this heading will be found special instructions which, if not complied with, could
result in damage to equipment and/or property.
These "Safety Alerts" alone cannot eliminate the hazards that they signal. Strict compliance with these spe-
cial Instructions plus "common sense" are major accident prevention measures.
NOTICE TO USERS OF THIS MANUAL
This SERVICE MANUAL has been written and published by Generac to aid our dealers' mechanics and com-
pany service personnel when servicing the products described herein.
It is assumed that these personnel are familiar with the servicing procedures for these products, or like or
similar products manufactured and marketed by Generac. That they have been trained in the recommended
servicing procedures for these products, including the use of common hand tools and any special Generac
tools or tools from other suppliers.
Generac could not possibly know of and advise the service trade of all conceivable procedures by which a
service might be performed and of the possible hazards and/or results of each method. We have not under-
taken any such wide evaluation. Therefore, anyone who uses a procedure or tool not recommended by
Generac must first satisfy himself that neither his nor the products safety will be endangered by the service
procedure selected.
All information, illustrations and specifications in this manual are based on the latest product information
available at the time of publication.
When working on these products, remember that the electrical system and engine ignition system are capa-
ble of violent and damaging short circuits or severe electrical shocks. If you intend to perform work where
electrical terminals could be grounded or touched, the battery cables should be disconnected at the battery.
Any time the intake or exhaust openings of the engine are exposed during service, they should be covered to
prevent accidental entry of foreign material. Entry of such materials will result in extensive damage when the
engine Is started.
During any maintenance procedure, replacement fasteners must have the same measurements and strength
as the fasteners that were removed. Metric bolts and nuts have numbers that indicate their strength.
Customary bolts use radial lines to indicate strength while most customary nuts do not have strength mark-
ings. Mismatched or incorrect fasteners can cause damage, malfunction and possible injury.
REPLACEMENT PARTS
Components on Generac recreational vehicle generators are designed and manufactured to comply with
Recreational Vehicle Industry Association (RVIA) Rules and Regulations to minimize the risk of fire or explo-
sion. The use of replacement parts that are not in compliance with such Rules and Regulations could result
in a fire or explosion hazard. When servicing this equipment, It is extremely important that all components be
properly installed and tightened. If Improperly Installed and tightened, sparks could Ignite fuel vapors from
fuel system leaks.
!
!

PART TITLE
1 THE AC GENERATOR
2 ENGINE MECHANICAL
3 GASOLINE FUEL SYSTEM
4 GASEOUS FUEL SYSTEM
5 ENGINE OIL & COOLING SYSTEM
6 ENGINE ELECTRICAL SYSTEM
7 TROUBLESHOOTING
8 SPECIFICATIONS & CHARTS
SERIES IMPACT 36 PLUS II
TABLE OF CONTENTS
SERVICE
MANUAL

Page 1
PART 1
GENERAL
INFORMATION
COMPUTER
CONTROLLED
VARIABLE
SPEED RV
GENERATORS
Series Impact 36 Plus II
SECTION TITLE
1.1 GENERATOR FUNDAMENTALS
1.2 GENERATOR MAJOR COMPONENTS
1.3 OPERATIONAL ANALYSIS
1.4 INSULATION RESISTANCE
1.5 COMPONENTS TESTING
1.6 CONTROL PANEL
1.7 SHEET METAL

NOTES

Section 1.1
GENERATOR FUNDAMENTALS
MAGNETISM
Magnetism can be used to produce electricity and
electricity can be used to produce magnetism.
Much about magnetism cannot be explained by our
present knowledge. However, there are certain pat-
terns of behavior that are known. Application of these
behavior patterns has led to the development of gen-
erators, motors and numerous other devices that uti-
lize magnetism to produce and use electrical energy.
See Figure 1. The space surrounding a magnet is
permeated by magnetic lines of force called "flux".
These lines of force are concentrated at the magnet's
north and south poles. They are directed away from
the magnet at its north pole, travel in a loop and re-
enter the magnet at its south pole. The lines of force
form definite patterns which vary in intensity depend-
ing on the strength of the magnet. The lines of force
never cross one another. The area surrounding a
magnet in which its lines of force are effective is
called a "magnetic field".
Like poles of a magnet repel each other, while unlike
poles attract each other.
Figure 1. Magnetic Lines of Force
ELECTROMAGNETIC FIELDS
All conductors through which an electric current Is
flowing have a magnetic field surrounding them. This
field is always at right angles to the conductor. If a
compass is placed near the conductor, the compass
needle will move to a right angle with the conductor.
The following rules apply:
• The greater the current flow through the conductor,
the stronger the magnetic field around the conductor.
• The increase in the number of lines of force is
directly proportional to the increase in current flow
and the field is distributed along the full length of
the conductor.
• The direction of the lines of force around a conduc-
tor can be determined by what is called the "right
hand rule". To apply this rule, place your right hand
around the conductor with the thumb pointing in the
direction of current flow. The fingers will then be
pointing in the direction of the lines of force.
NOTE: The "right hand rule" is based on the "cur-
rent flow" theory which assumes that current
flows from positive to negative. This is opposite
the "electron" theory, which states that current
flows from negative to positive.
Figure 2. The Right Hand Rule
ELECTROMAGNETIC INDUCTION
An electromotive force (EMF) or voltage can be pro-
duced in a conductor by moving the conductor so that
it cuts across the lines of force of a magnetic field.
Similarly, if the magnetic lines of force are moved so
that they cut across a conductor, an EMF (voltage)
will be produced in the conductor. This is the basic
principal of the revolving field generator.
Figure 3, below, illustrates a simple revolving field
generator. The permanent magnet (Rotor) is rotated
so that its lines of magnetic force cut across a coil of
wires called a Stator. A voltage is then induced into
the Stator windings. If the Stator circuit is completed
by connecting a load (such as a light bulb), current
will flow in the circuit and the bulb will light.
Figure 3. A Simple Revolving Field Generator
Page 1.1-1

Section 1.1
GENERATOR FUNDAMENTALS
ALTERNATING CURRENT
A simple generator consists of a coil of wires called a
Stator and a magnetic field called a Rotor. As the
Rotor's magnetic field cuts across the Stator coil, a
voltage is induced into the Stator windings. The
amount of induced voltage is equal to the strength of
the magnetic field.
See Figure 4. The current alternates according to the
position of the Rotor's poles in relation to the position
of the Stator. At 0° and again at 180°, no current flow
is produced. At 90° of Rotor rotation, current flow
reaches a maximum positive value. Rotor rotation to
270° brings another maximum flow of current.
However, at 270° the current flow has reversed in
polarity and now flows in the opposite direction.
ELECTRICAL UNITS
AMPERE:
The rate of electron flow in a circuit is represented by
the AMPERE. The ampere is the number of electrons
flowing past a given point at a given time. One
AMPERE is equal to just slightly more than six thou-
sand million billion electrons per second.
With alternating current (AC), the electrons flow first
in one direction, then reverse and move in the oppo-
site direction. They will repeat this cycle at regular
intervals. A wave diagram, called a "sine wave"
shows that current goes from zero to maximum posi-
tive value, then reverses and goes from zero to maxi-
mum negative value. Two reversals of current flow is
called a cycle. The number of cycles per second is
called frequency and is usually stated in "Hertz".
Figure 5. Alternating Current Sine Wave
VOLT:
The VOLT is the unit used to measure electrical
PRESSURE, or the difference in electrical potential
that causes electrons :o flow. Very few electrons will
flow when voltage is weak. More electrons will flow as
voltage becomes stronger. VOLTAGE may be consid-
ered to be a state of unbalance and current flow as
an attempt to regain balance. One volt is the amount
of EMF that will cause a current of 1 ampere to flow
through 1 ohm of resistance.
Page 1.1-2
Figure 4. Operation of a Simple Generator

Section 1.1
GENERATOR FUNDAMENTALS
Figure 6. Electrical Units
OHM:
The OHM is the unit of RESISTANCE. In every circuit
there is a natural resistance or opposition to the flow
of electrons. When an EMF is applied to a complete
circuit, the electrons are forced to flow in a single
direction rather than their free or orbiting pattern. The
resistance of a conductor depends on (a) its physical
makeup, (b) its cross-sectional area, (c) its length,
and (d) its temperature. As the conductor's tempera-
ture increases, its resistance increases in direct pro-
portion. One (1) ohm of resistance will permit one (1)
ampere of current to flow when one (1) volt of electro-
motive force (EMF) is applied.
OHM'S LAW
A definite and exact relationship exists between
VOLTS, OHMS and AMPERES. The value of one can
be calculated when the value of the other two are
known. Ohm's Law states that in any circuit the current
will increase when voltage increases but resistance
remains the same, and current will decrease when
resistance Increases and voltage remains the same.
Figure 7.
If AMPERES is unknown while VOLTS and OHMS
are known, use the following formula:
AMPERES = VOLTS
OHMS
If VOLTS is unknown while AMPERES and OHMS
are known, use the following formula:
VOLTS = AMPERES x OHMS
If OHMS is unknown but VOLTS and AMPERES are
known, use the following:
OHMS = VOLTS
AMPERES
REACTANCE IN AC CIRCUITS
GENERAL:
When direct current (DC) is flowing, the only opposi-
tion to current flow that must be considered is resis-
tance (ohms). This is also true of alternating current
(AC) when only resistance type loads such as heating
and lamp elements are on the circuit. In such a case,
current will be in phase with voltage- that is, the cur-
rent sine wave will coincide in time with the voltage
sine wave.
However, two factors in AC circuits called INDUC-
TIVE and CAPACITIVE REACTANCE will prevent the
voltage and current sine waves from being in phase.
INDUCTIVE REACTANCE:
This condition exists when current lags behind volt-
age (Figure 8). As current flows in a circuit, magnetic
lines of force are created at right angles to the con-
ductor. The continuous changes in current value
(from positive to negative) cause these magnetic lines
to collapse and build up continuously.
The magnetic field around the conductor induces
electromotive forces that cause current to keep on
flowing while voltage drops. The result is a condition
in which voltage leads current. When a conductor is
formed into a coil, the magnetic lines of force are con-
centrated in the center of the coil. This increased den-
sity causes an increase in magnetically Induced EMF
without increasing current Thus, coils cause inductive
reactance.
Inductive reactance can also be caused by placing an
induction motor on the circuit which utilizes the cur-
rent's magnetic field for excitation.
Figure 8. Inductive Reactance
Page 1.1-3

Section 1.1
GENERATOR FUNDAMENTALS
CAPACITIVE REACTANCE:
This condition occurs when current leads voltage
(Figure 9). It might be thought of as the ability to oppose
change in voltage. Capacitance exists in a circuit when
certain devices are ~a) capable of storing electrical
charges as voltage increases and (b) discharging these
stored charges when the voltage decreases.
Figure 9. Capacitive Reactance
WHAT IS AN "IMPACT PLUS" UNIT?:
The Impact Plus is a computer controlled generator
that uses an inverter to create a superior sine wave
and maintain a steady frequency. These units are dif-
ferent from conventional generators in that the perfor-
mance of the engine and AC generator are more
accurately matched over a wide range of power
needs. The Impact Plus computer controlled genera-
tor provides greater efficiency of both the engine and
the generator while maintaining electrical output with-
in an acceptable voltage range. The frequency is con-
trolled by the inverter and is maintained at a steady
60 Hz signal throughout the load range.
Computer controlled generator units have the ability
to operate the engine over a wide range of speeds,
while conventional generators will deliver correct AC
frequency and voltage only at a fixed rpm.
Unlike conventional AC generators, the Impact Plus
unit can match engine speed to load requirements.
This provides several advantages, as follows:
• Smaller engines can be used to produce more
power than on a conventional generator, since it
can be allowed to run at a higher speed.
• When the load is reduced, the engine can run at
slower than the usual speeds. This improves fuel
economy and reduces engine noise.
• The Impact Plus unit can be operated closer to its
peak power point at all times, because output volt-
age and current are functions of engine speed. This
allows for a much more compact generator design.
IMPACT PLUS SYSTEM OVERVIEW:
Figure 10 is a block diagram of the Impact Plus sys-
tem. The major elements of the system are represent-
ed in the diagram. Operation of the system may be
described briefly as follows:
1. The engine is directly coupled to a permanent magnet type
Rotor, so the Rotor runs at the same speed as the engine.
2. As the Rotor turns, its magnetic field cuts across the Stator
windings to induce a voltage into the Stator.
Page 1.1-4
Figure 10. Block Diagram of the Impact 36 Plus System