engine drives

8/9/2019 Engine Drives

1/19

ENGINE DRIVEN ELECTRICAL POWER GENERATION

Generator Type power sources convert mechanical energy or mechanical power that is obtained from an inter-

nal combustion engine into electrical power suitable for arc welding and/or auxiliary electrical power. For

welding, two basic types of rotating power sources are used, the generator and the alternator. Both designs

have a rotating member, called a rotor. A system of magnetic field excitation is needed for both types.

There are three essentials for electrical power generation:

1. Magnetic Lines of Force (Magnetic Field)2. Electrical Current Carrying Conductor

3. Relative Motion Between the Magnetic Field and the Electrical Current Carrying Conductor.

In electrical power generation, there must be relative motion between a magnetic field and a current carrying

conductor. Whenever a wire moves through the lines of force of a magnetic field or whenever lines of force of

a magnetic field are moved through a wire, a voltage is induced in the wire. This induced voltage causes elec-

tric current to flow when the circuit is complete. Thus, the principle of any rotating power source is that elec-

trical current is produced in electrical conductors (coil of wire) when they are moved through a magnetic field.

Physically, it makes no difference whether the magnetic field moves or the conductor moves, just so that the

coil experiences a changing magnetic field intensity.

Page 1


2/19Page 2

The amount of voltage generated depends upon the number lines of force cut per second. Three ways ofincreasing the voltage from a generator are (1) by increasing the motion (speed/velocity)of the magnetic field

(or the coil), (2) by using a stronger magnet (or magnetic field), and (3) by increasing the number of turns of

wire in the coil.

A direct current generator consists of a rotor and a stator. The stator or the stationary portion of the generator,

within which the rotor assembly turns, holds the electromagnetic field coils which conduct a small amount of

direct current to maintain the necessary continuous electromagnetic field excitation required for power genera-

tion. Direct current is used to create the electromagnetic field. The direct current for the field windings of the

generator is called the exciting current, and the generator that supplies the direct current is called the exciter.

This direct current amperage is normally no more than 10 to 15 ampere and very often is less. Electromagnets

provide stronger magnetic fields and control the amount of induced current. This control is important, for

when the amount of current flowing through the electromagnets is changed, the strength of the magnetic field

is changed.

The rotor assembly consists of (1) a through shaft, (2) two end bearings to support the rotor and shaft load, (3)

an armature which includes the laminated armature iron core and the current-carrying armature coils. It is in

the armature coils that the electrical welding power is generated. And (4) a commutator brush arrangement for

mechanically rectifying or changing alternating current to direct current welding power.

In actual practice, the armature turns within the stator and its electromagnetic field system, and welding cur-

rent is generated. The AC voltage produced by the armature coils moving through the magnetic field of the

stator is carried to the copper commutator bars through electrical conductors from the armature coils. The

commutator is located at one end of the armature. The commutator is a system of copper bars mounted on the

rotor shaft. The conductors are soft-soldered to individual commutator bars. The latter may be considered as

terminals, or "collector bars," for the alternating current generated from the armature. It is a group of conduct-

ing bars arranged parallel to the rotating shaft to make switching contact with a set of stationary carbon brush-

es (contact points). These bars are connected to the armature conductors. The whole arrangement is construct-

ed in proper synchronization with the magnetic field. As the armature rotates, the commutator performs the

function of mechanical rectification.

Each copper bar has a machined and polished top surface. Carbon contact brushes ride on that top surface to

pick up each half-cycle of the generated alternating current. The carbon contact brushes pick up each half-


3/19

cycle of generated alternating current and direct it into a conductor as direct current. The purpose of the com

mutator is to carry both half-cycles of the generated AC sine wave, but on separate copper commutator bars.

Each of the copper commutator bars is insulated from all the other copper bars.

Page 3

INDUCED

VOLTAGE

TIME N SAC

HERE

COMMUTATOR

DC HERE

()

(+)

VOLTAGE AT BRUSHES

The magnetic field is contained in the stator assembly of a generator. It is in the armature coilsthat welding power is generated. The commutator-brush rectifies ac to dc welding power.

2 POLEGENERATOR

DC Generator

Normally, the direct current generator is a three-phase electrical device. Three-phase welding systems normal-

ly provide the smoothest welding power of any of the electromechanical welding power sources.

1. END VIEW OF THE ARMATURE ANDFIELD COILS OF GENERATOR

2. END VIEW OF FOUR POLE ROTORAND STATOR OF ALTERNATOR


4/19

MILLER ALTERNATOR DESIGN VS. GENERATOR DESIGN

The entire line, of Miller Electric's engine driven power sources, uses a design concept called the "revolving

(electromagnetic) field design." This concept is commonly called an alternator design (often called an alternat-

ing current generator). This design in welding power sources is in direct contrast to how DC generator rotating

power sources are designed. There are distinct differences and advantages to using alternator design over the

DC generator design. It is very similar, except the alternator rotor assembly contains the electromagnetic field

coils instead of the stator coils as found in generators. The heavy current-carrying conductor windings are

wound into the stator. These machines are also called revolving or rotating field machines.

Slip rings are used to conduct low DC power into the rotating member to produce a rotating electromagnetic

field. An alternator usually has brushes and slip rings to provide the low direct current power to the field coils.

It is not usual practice in alternators to feed back part of the welding current to the field circuit. Rather the

alternator usually uses the brushes and slip rings to provide the low DC power to the field coils. The voltage

induced in the armature coil passes through a set of slip rings connected to the ends of the armature coil and

through a set of brushes making contact with the slip rings, to an external circuit. This configuration precludes

the necessity of the commutator and the brushes used with DC output generators.

The welding output is alternating current, which requires external rectification for direct current applications.

Rectification is usually done with a bridge rectifier using silicon diodes. Both single and three-phase alterna-

tors are available to supply AC to the necessary rectifier system. The DC welding characteristics are similar to

those of single and three-phase transformer-rectifier units.

Page 4


5/19

The alternator design presents several fundamental advantages. Some important facts are:

Page 5

Miller Alternator Design

1. Higher duty cycle - 100%- Design permits 100% duty cycle rating.

2. Operates cooler

- Most heat is generated in the weld windings.located on the outside of the unit.

- Easy to cool.- Minimum cold to hot drift.

3. Low currents in moving parts- Rotating field coils carry less than 10 amps.

4. No brush-commutator assembly- Slip rings and brush carry less than 10 amps.

- Minimum brush wear.- No chance of polarity changing.

5. Rotor is lighter- Quicker to accelerate to speed.- Rotates easier, engine easily handles 300 amppower source.

- Less fuel consumption for same amperageoutput.

6. No "kits" required for paralleling- Hook any number of units together for increased

output.- No current feedback can occur since diodesblock feedback.

Generator Design

Lower duty cycle - 60%- To obtain higher duty cycle requires heavier

windings in the armature.- Small units are usually 30-50% duty cycle rated.

Harder to cool

- Heat is generated in the armature. Must be cooledby air movement and conduction to the outside ofthe unit.

- More heat build up, greater cold to hot drift. Outputwill drop off when unit heats up.

High current in moving parts- Armature carries full welding current. Heat builds

up internally.

Brush assembly and commutator bars- Brushes must carry full welding current.

- Arcing occurs.- Brushes wear, lowering efficiency, maintenancerequired.

- Welding polarity may change during welding whenbrushes lift off the commutator.

- Commutator will require maintenance.

Armature is a large mass of iron- Slower to respond.- Engine can only handle a 200 amp power source.- More torque required to rotate. Harder on bearings,

etc.- During heavy usage such as arc gouging, stress

relieving, etc. heat buildup will cause solder to bethrown from commutator area.

Special kits required to parallel- Adapter kits required to connect units together.

Current feedback from one unit to another causesone to "drive" the other as a motor.

ROTATING MAGNETICFIELD COIL DESIGN

ROTATING ARMATURE

OF AN ALTERNATOR100% DUTY CYCLE

DESIGN OF AGENERATOR

60% DUTY CYCLE

ROTOR COMPARISONS


6/19

The blocking nature of the rectifiers makes direct current alternator units easy to operate in parallel for obtain-

ing increased welding current output by connecting two or more welding alternators (generators) in parallel.

Care should be taken to ensure that connections are the same polarity. All units paralleled must be set to deliv-

er equal welding (amperage & polarity) outputs. Parallel connection is not advised unless the manufacturer's

specific instructions are followed. Such a precaution is necessary because successful paralleling depends upon

matching the output-voltage, output amperage setting, and polarity of each machine.

In the case of self-excited generators, the problem may be further complicated by the necessity to equalize the

excitation between the generators.

Both the generator and alternator type power sources generally provide welding current adjustment in broad

steps called ranges. A rheostat or other control is usually placed in the electromagnetic field circuit to adjust

the internal magnetic field strength for fine adjustment of power output. The fine adjustment of welding power

output regulates the strength of the magnetic field, and will also change the open circuit voltage. When the

rheostat is adjusted near the bottom of the range with a low rheostat setting, the open circuit voltage will nor-

mally be substantially lower than at the high end of the range.

Page 6

Typical Engine Drive Amperage Control

With many alternator power supplies, broad ranges are obtained from taps on a reactor in the AC portion of

the circuit. As such, the basic machine does not often have the dynamic response required for shielded metal

arc welding. Thus, a suitable inductor is generally inserted in series connection in one leg of the DC output

from the rectifier. Welding generators do not normally require an inductor.

There is a limited range of overlap normally associated with rotating equipment where the desired welding

current can be obtained over a range of open circuit voltages. If welding is done in this area, welders have the

capability to fine tune or adjust the arc to the job. With a lower open circuit voltage, the slope of the voltam-

pere curve is less. This allows the welder to regulate the welding current to some degree by varying the arc

length. This can assist in weld-pool control, particularly for out-of-position welding.

A generator or an alternator unit produces a maximum or a finite amount of power that is measured in kilo-

watts. As the voltage increases the amperage will decrease proportionately. Conversely as the voltage decreas-

es the amperage will increase proportionately. In other words, if there is a relatively high open circuit voltage

at some particular setting on a power source, there must be a relatively limited amount of maximum short cir-

cuit current at the same time.


7/19

Volt-Amp Curves

Welding power sources are available that produce both constant current and constant voltage. These units are

used for field applications where both are needed at the job site when primary, utility power is not available.

Also, many new designs use electronic solid-state circuitry to obtain a variety of volt-ampere characteristics.

Saturable reactors and moving-core reactors may be used for output control of these machines. The normal

method is to provide a tapped reactor for broad control of current ranges, in combination with control of the

alternator magnetic field to produce fine control within these ranges.

ENGINE DRIVE AUXILIARY POWERMILLER welding generators are combination welding and power generators specifically designed for the

welding application. An auxiliary power winding is included in the generator to provide convenience power

incidental to the welding operation for accessory equipment. Most auxiliary power generators are singlephase

and may be either two-wire or three-wire design depending upon the model. There is no significant advantage

of the two-wire system versus the three-wire except that the three-wire design is capable of supplying two dif-

ferent voltages simultaneously (120/240 VAC).

These machines are designed to provide nominal 120 or 240 volts, 60 Hertz power, which are the common

small load voltages in the United States. Different voltages and frequencies are found in various parts of the

world and optional auxiliary power generator designs are available for these requirements. These generators

can be used to power portable tools, lights, heaters, compressors, pumps, etc., within the capabilities of the

unit. They are not designed to power voltage and/or frequency sensitive electronic equipment which may be

damaged by voltage or frequency changes normal to the operation.

An alternator or generator may be either self-excited or separately-excited, depending on the source of the

field power. Either unit may use a small auxiliary alternator or generator, with the rotor on the same shaft as

the main rotor, to provide exciting power. On many engine-driven units, a portion of exciter field power is

available to operate tools or lights necessary to the welding operation. In the case of a generator, this auxiliary

power is usually 115 volts of direct current. With alternator-type power source, 120 or 120/240 volts of alter-

nating current is usually available. Alternating Current Voltage frequency (hertz) depends upon the engine

Page 7

The volt-ampere curves show theminimum and maximum voltageand amperage output capabilities ofthe welding generator. Curves of allother settings fall between thecurves shown.

0

20

40

60

80

100

0 100 200 300 400 500 600 700 800 900

DC AMPERES

DC

VOLTS

Ranges

300Max185425

125320 85190

5590


8/19

speed. The frequency of the output welding current is controlled by the rotation of the rotor assembly and by

the number of poles in the alternator design. A two-pole alternator must operate at 3600 rpm to produce

60 Hz alternating current, whereas a four-pole alternator design must operate at 1800 rpm to produce 60 Hz

alternating current.

Page 8

N S

AC HERE

DCHERE

2 Pole Alternator With Tapped

FINE AMPERAGEADJUSTMENT

TAPPEDREACTOR

STABILIZER(INDUCTOR)Reactor For Coarse Current

Control And Adjustable MagneticField Amperage For Fine CurrentOutput Control

Design:

1. Two Pole Alternator

2. Four Pole Alternator


9/19

Considerations:

1. Generator Sizing

2. Load Analysis

Rated Output

Found on machine nameplate

E.G. Trailblazer 301: 9,500 Watts

120 Volts - 84 Amps

240 Volts - 42 Amps

kVA while welding is dependent on welding output

Page 9

Two Pole Alternator

Four Pole Alternator


10/19

1. Generator Sizing: How Much Power Can Generator Supply?

Page 10

Limits of a Generator

MILLER welding generators are designed to operate at maximum load, but doing so allows very little reserve

engine horsepower to follow changes in load requirements. This makes itself known by noticeable voltage and

frequency changes (light bulbs flicker, etc.) Much improved voltage and frequency regulation can be realized

by not loading the generator to 100% of its capacity. For best performance and load handling, only use approx-imately 90% of the available output. The 10% margin allows for more satisfactory engine governor response

to changing load situations. The rule becomes simple: Always know the total load requirements and the gener-

ator's capability. Select a generator to adequately meet load requirements, or limit load requirements to the

capabilities of the existing generator.

2. Load Analysis: How Much Power Does Equipment Require?


11/19

Load analysis and generator sizing are essential for satisfactory generator and equipment operation. The avail-

able auxiliary power is limited by engine horsepower and is a small, finite power system as compared to the

large, seemingly-infinite electric utility system. Any single load may represent usage of a large portion of the

total power available. It is necessary to carefully determine the total load that will be applied by adding up all

the individual loads. Some tools are rated in watts, others in amperes. Lights and heaters are rated in watts.

Most equipment will specify on its nameplate what its specific requirements will be.

For example, a drill requires 4.5 amperes at 115 volts. Watts equals volts times amperes. Therefore, this drill

requires approximately 520 watts. Add three 200 watt flood lamps, and requirements increase by 600 watts for

a total of 1120 watts. Continue in this fashion until all loads have been added. Be sure to add all motor run-

ning requirements to the total (motor starting requirements will be discussed later). Consider also that a load is

not always constant. To be sure, lights and resistance heaters are constant, but portable power tools are not.

One rarely grinds or drills with a constant, even pressure. Thus, the load requirements change greater than

anticipated. Induction motors normally power loads that require variable amounts of power from the generator

and will be discussed later.

Page 11

VOLTS x AMPERES = WATTS

This equation provides an actual power requirement for resistive loads, or an approximate running requirement for non-resistive loads.

EXAMPLE 1:If a drill requires 4.5 amperes at 115 volts, calculate its running power requirement in watts.

115 V x 4.5 A = 520 W

Therefore, the individual load applied by the drill is 520 watts.

EXAMPLE 2:If a flood lamp is rated at 200 watts, the individual load applied by the lamp is 200 watts. If three 200 watt floodlamps are used with the drill from Example 1, add the individual loads to calculate total load.

Therefore, the total load applied by the three flood lamps and drill is 1120 watts.

(200 W + 200 W + 200 W) + 520 W = 1120 W

Calculating Power Required To Run Equipment


12/19Page 12

S-0624

1 Motor Start Code

2 Running Amperage

3 Motor HP

4 Motor Voltage

To find starting amperage:

Step 1:Find code and use table tofind kVA/HP. If code is not listed,multiply running amperage by six tofind starting amperage.

Step 2: Find Motor HP and Volts.

Step 3:Determine starting amper-age (see example).

Welding generator amperage out-put must be at least twice themotors running amperage.

VOLTS AMPS

HP

230 2.5

1/4

Hz

PHASE

CODE 60

1

M

AC MOTOR1

2

3

4

Single-Phase Induction Motor Starting Requirements

Motor StartCode G H J K L M N P

KVA/HP 6.3 7.1 8.0 9.0 10.0 11.2 12.5 14.0

EXAMPLE: Calculate the starting amperage required for a 230 V, 1/4HP motor with a motor start code of M.

Starting the motor requires 12.2 amperes.11.2 x 1/4 x 1000

230= 12.2 A

kVA/HP x HP x 1000

VOLTS= STARTING AMPERAGE

Volts = 230 HP = 1/4 Using Table, Code M results in kVA/HP = 11.2

Starting Motors

Different types of loads require different types of output from the generator. When a nonmotor load is applied,

generator output goes to the ampere requirement of the equipment, but voltage remains near rated. The non-

motor load does not cause the voltage to drop significantly below its nominal rating. When a motor load is

applied, the generator will attempt to supply motor starting current causing output voltage to drop to nearly

zero volts because the starting current is many times the running current. For this reason, it is necessary to

determine the starting amperage required by the motor and verify the the generator can supply that amount of

amperage. This can be done using the formula shown below, or by using the charts shown on the followingpages.

Caculating Motor Starting Requirements


13/19Page 13

Industrial Motors Rating Starting Watts Running Watts

Split Phase 1/8 HP 800 300

1/6 HP 1225 500

1/4 HP 1600 600

1/3 HP 2100 700

1/2 HP 3175 875

Capacitor Start-Induction Run 1/3 HP 2020 720

1/2 HP 3075 9753/4 HP 4500 1400

1 HP 6100 1600

1-1/2 HP 8200 2200

2 HP 10550 2850

3 HP 15900 3900

5 HP 23300 6800

Capacitor Start-Capacitor Run 1-1/2 HP 8100 2000

5 HP 23300 6000

7-1/2 HP 35000 8000

10 HP 46700 10700

Fan Duty 1/8 HP 1000 400

1/6 HP 1400 550

1/4 HP 1850 6501/3 HP 2400 800

1/2 HP 3500 1100

Farm/Home Equipment Rating Starting Watts Running Watts

Stock Tank De-Icer 1000 1000

Grain Cleaner 1/4 HP 1650 650

Portable Conveyor 1/2 HP 3400 1000

Grain Elevator 3/4 HP 4400 1400

Milk Cooler 2900 1100

Milker (Vacuum Pump) 2 HP 10500 2800

FARM DUTY MOTORS 1/3 HP 1720 720Std. (e.g. Conveyors, 1/2 HP 2575 975

Feed Augers, Air 3/4 HP 4500 1400

Compressors) 1 HP 6100 1600

1-1/2 HP 8200 2200

2 HP 10550 2850

3 HP 15900 3900

5 HP 23300 6800

High Torque (e.g. Barn 1-1/2 HP 8100 2000

Cleaners, Silo Unloaders, 5 HP 23300 6000

Silo Hoists, Bunk Feeders) 7-1/2 HP 35000 8000

10 HP 46700 10700

3-1/2 cu. ft. Mixer 1/2 HP 3300 1000

High Pressure 1.8 Gal/Min 500 PSI 3150 950

Washer 2 gal/min 550 PSI 4500 1400

2 gal/min 700 PSI 6100 1600

Refrigerator or Freezer 3100 800

Shallow Well Pump 1/3 HP 2150 750

1/2 HP 3100 1000

Sump Pump 1/3 HP 2100 800

1/2 HP 3200 1050

Approximate Power Requirements for Industrail Motors

Approximate Power Requirements for Farm/Home Equipment


14/19Page 14

Contractor Rating Starting Watts Running Watts

Hand Drill 1/4 in 350 350

3/8 in 400 400

1/2 in 600 600

Circular Saw 6-1/2 in 500 500

7-1/4 in 900 900

8-1/4 in 1400 1400

Table Saw 9 in 4500 150010 in 6300 1800

Band Saw 14 in 2500 1100

Bench Grinder 6 in 1720 720

8 in 3900 1400

10 in 5200 1600

Air Compressor 1/2 HP 3000 1000

1 HP 6000 1500

1-1/2 HP 8200 2200

2 HP 10500 2800

Electric Chain Saw 1-1/2 HP, 12 in 1100 1100

2 HP, 14 in 1100 1100

Electric Trimmer Standard 9 in 350 350

Heavy Duty 12 in 500 500Electric Cultivator 1/3 HP 2100 700

Elec. Hedge Trimmer 18 in 400 400

Flood Lights HID 125 100

Metal Halide 313 250

Mercury 1000

Sodium 1400

Vapor 1250 1000

Submersible Pump 400 gph 600 200

Centrifugal Pump 900 gph 900 500

Floor Polisher 3/4 HP, 16 in 4500 1400

1 HP, 20 in 6100 1600

High Pressure Washer 1/2 HP 3150 950

3/4 HP 4500 1400

1 HP 6100 1600

55 gal Drum Mixer 1/4 HP 1900 700

Wet & Dry Vac 1.7 HP 900 900

2-1/2 HP 1300 1300

Approximate Power Requirements for Contractor equipment


15/19

Auxiliary Power While Welding

Page 15

Weld Current Total Power 120 V Receptacle 240 V Receptaclein Amperes in Watts Amperes Amperes

0 10,000 84* 42*

90 8000 66* 33125 5200 43* 21

180 3500 29* 14

250 2200 18 9

Weld CurrentIn Amperes

300

250

200

150

100

0

Total Powerin Watts

1000

3500

5200

6700

8000

10000

120 V

ReceptacleAmperes

10

31

46

60

70

84

240 V

ReceptacleAmperes

5

15

23

30

35

42

Bobcat 250 Power While Welding

Trailblazer 301 Power While Welding

Typical Connections To Supply Standby Power

Generators may be used to provide emergency power to systems normally supplied by other sources of elec-

tricity, but extreme caution must be exercised to properly install the generator. The specific rules for installa-

tion and use of auxiliary generators are established by the National Electrical Code, state, local, and in some

cases OSHA codes. These codes were developed to assure personnel safety - vitally important for any user. Itis the responsibility of the installer to be familiar with and meet all installation requirements. Major require-

ments of the National Electrical Code (1990 edition) for auxiliary power plant installations are (1) overcurrent

protection as required for the generator, (2) proper grounding of the generator, and (3) isolation of the genera-

tor from other sources of power. Additional requirements may be established by state and local codes.

Overcurrent protection is required if a generator is supplying a permanent installation. Fuses or circuit break-

ers are adequate for small auxiliary power plants. Overcurrent protection is generally not required for genera-

tors supplying portable, cord-connected equipment through receptacles mounted on the generator.


16/19

Customer-supplied equipment is required if generator is to supply standby power during emergencies or power

outages. Locate the power company service meter (Item 1), and main and branch overcurrent protection (Item

2), and install equipment as shown below.

Page 16

Have only qualified personsperform these connectionsaccording to all applicablecodes and safety practices.

1 Power Company ServiceMeter

2 Main and Branch OvercurrentProtection

3 Double-Pole, Double-ThrowTransfer Switch

Obtain and install correct switch.Switch rating must be same as orgreater than the branch overcurrentprotection.

4 Circuit Breakers or FusedDisconnect Switch

Obtain and install correct switch.

5 Extension Cord

Select as shown in Section 13-11.

6 Generator Connections

Connect terminals or plug of ade-quate amperage capacity to cord.Follow all applicable codes andsafety practices.

Turn off or unplug all equipmentconnected to generator beforestarting or stopping engine. Whenstarting or stopping, the engine haslow speed which causes low volt-age and frequency.

7 Load Connections

Customer-supplied equipment is required ifgenerator is to supply standby power duringemergencies or power outages.

120/240 Volt60 Hz

Three-WireService

240 V

120 V

120 V

Neutral

240 V

120 V

120 V120/240 VoltSingle-PhaseThree-Wire

Generator Output

Connection Ground

F1

or

CB

240 V

120 V

120 VLoad

1

2 3

6

74

5

Item 4 is not necessary if circuitprotection is already present inwelding generator auxiliarypower output circuit.

Standby Power Equipment And Connections


17/19

Selecting Extension Cords

Use the tables below to select extension cords. Use shortest cords possible because long cords may reduce out-

put or cause unit overload.

Page 17

Cord Lengths for 120 Volt Loads

If unit does not have GFCI receptacles, use GFCI-protected extension cord.

Maximum Allowable Cord Length in ft (m) for Conductor Size (AWG)*

Current(Amperes)

Load (Watts) 4 6 8 10 12 14

5 600 350 (106) 225 (68) 137 (42) 100 (30)

7 840 400 (122) 250 (76) 150 (46) 100 (30) 62 (19)

10 1200 400 (122) 275 (84) 175 (53) 112 (34) 62 (19) 50 (15)

15 1800 300 (91) 175 (53) 112 (34) 75 (23) 37 (11) 30 (9)

20 2400 225 (68) 137 (42) 87 (26) 50 (15) 30 (9)

25 3000 175 (53) 112 (34) 62 (19) 37 (11)

30 3600 150 (46) 87 (26) 50 (15) 37 (11)

35 4200 125 (38) 75 (23) 50 (15)

40 4800 112 (34) 62 (19) 37 (11)

45 5400 100 (30) 62 (19)

50 6000 87 (26) 50 (15)

*Conductor size is based on maximum 2% voltage drop

Cord Lengths for 240 Volt Loads

If unit does not have GFCI receptacles, use GFCI-protected extension cord.

Maximum Allowable Cord Length in ft (m) for Conductor Size (AWG)*

Current(Amperes)

Load (Watts) 4 6 8 10 12 14

5 1200 700 (213) 450 (137) 225 (84) 200 (61)

7 1680 800 (244) 500 (152) 300 (91) 200 (61) 125 (38)

10 2400 800 (244) 550 (168) 350 (107) 225 (69) 125 (38) 100 (31)

15 3600 600 (183) 350 (107) 225 (69) 150 (46) 75 (23) 60 (18)

20 4800 450 (137) 275 (84) 175 (53) 100 (31) 60 (18)

25 6000 350 (107) 225 (69) 125 (38) 75 (23)

30 7000 300 (91) 175 (53) 100 (31) 75 (23)

35 8400 250 (76) 150 (46) 100 (31)

40 9600 225 (69) 125 (38) 75 (23)

45 10,800 200 (61) 125 (38)

50 12,000 175 (53) 100 (31)

*Conductor size is based on maximum 2% voltage drop


18/19

Engine and Fuel Choices

Rotating type power supplies are used for field erection and fabrication work when no electric power is avail-

able. For this use, a wide variety of internal combustion engines are available. Both liquid-cooled and air-

cooled engines are used. Gasoline is the most popular fuel because of price and availability. Diesel fuel is pop-

ular because of its high flash point. Also, some regulations will permit only diesel fuel for engines used in spe-

cific applications. A good example is the use of diesel engines for welding power sources on offshore drilling

rigs and marine applications. Propane and natural gas are used in some applications because it is cleaner burn-

ing than gasoline. However, they require a special carburetion system. An example of the need for these clean-er burning fuels is "in plant" maintenance welding.

Engine driven power sources are often equipped with idling devices to save fuel. These devices are automatic

in that the engine will run at a set idle speed until the electrode is touched to the work or a load is sensed on

the auxiliary power outlet. Under idling conditions, the open circuit voltage of the alternator/generator is low.

Touching the electrode to the work energizes a sensing circuit that automatically accelerates the engine to the

operating speed. When the arc is broken, the engine will return to its idle speed after a set time.

Page 18

The curve shows typical fuel useunder weld or power loads.

193 093

1800 RPM

IDLE

Fuel Consumption

Engine driven power sources are available with many auxiliary features. Units may be equipped with a remote

output control attachment. It may be either fingertip, hand, or foot control operated so that the operator may

take the power source adjustment (contactor, voltage and/or amperage) to the work area while welding.

Other auxiliary features that can be obtained on the engine driven welding machines are: polarity switches (to

easily change from DCEN to DCEP), running hour meters, fuel gauges, battery chargers, high-frequency arc

starters, and volt/ampere meters. Some larger units are equipped with an air compressor for carbon arc air cut-

ting and gouging, plasma arc cutting and gouging, and operating pneumatic hand tools.


19/19

Why Buy A Diesel Engine Powered Welder?

- It uses approximately half as much fuel as a similar sized gasoline engine.

- It has no points, plugs, condenser or carburetor, which means no downtime from costly tune-ups and

adjustments.

- It doesn't have carburetor icing problems in severe cold climates or fuel and vapor lock problems in severe

warm climates.

- It is less apt to be pilfered for personal use than gasoline due to lack of diesel fueled automobiles, and it's a

more common fuel for the large construction machinery.- It will be running long after a gasoline engine has had to be overhauled.

- It is safer fuel to use than gasoline, which is very important on construction job sites, on offshore rigs and in

the oil fields.

engine drives

Documents