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: (262) 473-5514 Fax: (262) 472-6505

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

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