ESAB PHC-402 Cutting Power Supply Troubleshooting instruction

Brand: ESAB

Model: PHC-402 Cutting Power Supply

Category: Welding System

Type: Troubleshooting instruction

ESAB PHC-402 Cutting Power Supply is a high-powered plasma cutting solution for industrial applications. With a rated output of 400 Amps at 215 Volts DC, it can deliver clean, precise cuts in various commercial metals. Its robust construction and advanced features make it suitable for demanding cutting tasks, including mechanized operations.

The PHC-402 offers a wide output current range of 100-500 Amps, allowing you to tailor the cutting performance to the material thickness and desired cut quality. Its steep volt-ampere curve characteristics ensure stable arc performance, resulting in consistent and high-quality cuts.

F-14-260

April, 1984

PHC-402

CUTTING POWER SUPPLY

These INSTRUCTIONS are for experienced operators. Do NOT use with any process other than plasma cutting.

This unit has a high voltage output designed for plasma cutting only. If you are not fully familiar with the principles

of operation and safe practices for electric welding equipment, we urge you to read ESAB's free booklet, "Precau-

tions and Safe Practices for Electric Welding and Cutting, " Form 52-529. Do not permit untrained persons to

install, operate, or maintain this equipment. Do not attempt to install or operate this equipment until you have read

and fully understand these instructions. If you do not fully understand these instructions, contact your supplier

for further information. Be sure to read the Safety Precautions on page 2 before installing or operating this equip-

ment.

*This 100% Duty is based on a cycle in which the fans are cooling,

with no load, for 30 minutes maximum, see Section I-B.

NOTE: Refer to local code requirements for correct plasma

cutting output cables. Do not use ordinary welding cable.

INSTRUCTIONS for

Be sure this information reaches the operator.

You can get extra copies through your supplier.

I. INTRODUCTION

The PHC-402 Power Supply (P/N 679500) is designed for high

speed plasma arc cutting applications. When used with suit-

able plasma arc cutting equipment, such as ESAB's mecha-

nized PCM-500 outfit (covered in Form 14-255), it is sufficiently

powered to provide high quality cuts in all types of commercial

metals. If greater cutting current capability is required, parallel

operation of these units is permissible -- please consult with

the factory for instructions. For additional operating data and

electrical characteristics of this machine, refer to the Specifica-

tion Table.

A. DESCRIPTION

The PHC-402 cutting power supply is a silicon controlled rec-

tifier (SCR), three-phase transformer/rectifier type d.c. unit with

solid state circuitry. The unit can be operated in a single, fully

balanced output current range from 100 to 500 amps. A current

control Panel-Remote Switch determines the location from

which the output current will be regulated; either locally from

the power supply front panel ("Panel" position) or remotely

from the control assembly ("Remote" position).

The PHC-402 is powered by a three-phase main transformer

which combines with solid state control to provide steep volt-

ampere curve output characteristics required for plasma cut-

ting. A three-phase full wave SCR and diode bridge rectifier is

used to convert the a.c. output current from the transformer to

d.c. cutting current, and also control the output current through

the SCR's. A network, of integrally-mounted capacitors and

resistors provide transient and high-frequency voltage pro-

SPECIFICATIONS

Rated

Output

Continuous Duty 400 Amp @ 215 Volts DC

100% Duty - 1/2 Hr.* 500 Amp @ 180 Volts DC

Output Current Range 100-500 Amps

Open Circuit Voltage 415 Volts DC

Input Voltage

460 VAC, 60 Hz, 3-Ph

380 VAC, 50 Hz, 3-Ph

415 VAC, 50 Hz, 3-Ph

Input Current

Rated Output

400 Amp

Output

130 Amp @ 460 VAC, 60 Hz

144 Amp @ 415 VAC, 50 Hz

158 Amp @ 380 VAC, 50 Hz

500 Amp

Output

163 Amp @ 460 VAC, 60 Hz

180 Amp @ 415 VAC, 50 Hz

198 Amp @ 380 VAC, 50 Hz

Power Factor @ Rated Load 0.85%

Dimensions

Width

Depth

Height

36.75 inches - 933.5 mm

43.50 inches - 1105 mm

31 inches - 787.4 mm

Weight 1830 l bs.-830 kg.

ESAB Welding &

Cutting Products

SAFETY PRECAUTIONS

WARNING: These Safety Precautions are for your protection. Be-

fore performing any installation or operating procedures, be sure to

read and follow the safety precautions listed below. Failure to ob-

serve these Safety Precautions can result in personal injury or death.

1. PERSONAL PROTECTION -- Skin and eye burns from exposure to

rays from an electric-arc or hot metal can be more severe than

sunburn. Therefore:

a. Use a face shield fitted with the correct filter and cover plates

to protect your eyes, face, neck, and ears from sparks and rays

of the arc when operating or observing operations. WARN by-

standers not to watch the arc and not expose themselves to the

rays of the electric-arc or hot metal.

b. Wear flameproof gauntlet type gloves, heavy long-sleeve shirt,

cuffless trousers, high-toppered shoes, and a welding helmet

or cap for hair protection, to protect against arc rays and hot

sparks or hot metal. A flameproof apron may also be desirable

as protection against radiated heat and sparks.

c. Hot sparks or metal can lodge in rolled up sleeves, trouser cuffs,

or pockets. Sleeves and collars should be kept buttoned, and

pockets eliminated from the front of clothing.

d. Protect other nearby personnel from arc rays and hot sparks

with a suitable non-flammable partition.

e. Always wear safety glasses or goggles when in a work area.

Use safety glasses with side shields or goggles when chipping

slag or grinding. Chipped slag may be hot and can travel con-

siderable distances. Bystanders should also wear safety glasses

or goggles.

f. Some gouging and cutting processes produce excessively high

noise levels and require ear protection.

2. FIRE PROTECTION -- Hot slag or sparks can cause serious fires

when in contact with combustible solids, liquids, or gases. There-

fore:

a. Remove all combustible materials well away from the work area

or completely cover the materials with a protective non-flam-

mable covering. Such combustible materials include wood,

clothing, sawdust, gasoline, kerosene, paints, solvents, natu-

ral gas, acetylene, propane, and similar combustible articles.

b. Hot sparks or hot metal can fall into cracks in floors or wall

openings and cause a hidden smoldering fire. Make certain

that such openings are protected from hot sparks and metal.

c. Do not weld, cut or perform other hot work until the workpiece

has been completely cleaned so that there are no substances

on the workpiece which might produce flammable or toxic va-

pors.

d. For fire protection, have fire extinguishing equipment handy

for instant use, such as a garden hose , water pail, sand bucket,

or portable fire extinguisher.

e. After completing operations, inspect the work area to make cer-

tain there are no hot sparks or hot metal which could cause a

fire later.

f. For additional information, refer to NFPA Standard 51B, "Fire

Prevention in Use of Cutting and Welding Processes", which is

available from the National Fire Protection Association,

Batterymarch Park, Quincy, MA 02269.

3. ELECTRICAL SHOCK -- Contact with live electrical parts can cause

severe burns to the body or fatal shock. Severity of electrical shock

is determined by the path and amount of current through the body.

Therefore:

a. Never allow live metal parts to touch bare skin or any wet cloth-

ing. Be sure gloves are dry.

b. When standing on metal or operating in a damp area, make cer-

tain that you are well insulated. Wear dry gloves and rubber-

soled shoes and stand on a dry board or platform.

c. Always ground the power supply by connecting a ground wire

between the power supply and an approved electrical ground.

d. Do not use worn or damaged cables. Do not overload the cable.

Use well maintained equipment.

e. When not operating, turn off the equipment. Accidental ground-

ing can cause overheating and create a fire hazard. Do not coil

or loop cable around parts of the body.

f. Be sure the proper size ground cable is connected to the

workpiece as close to the work area as possible. Grounds con-

nected to building framework or other remote locations from

the work area increase the possibility of output current passing

through lifting chains, crane cables, or various electrical paths.

g. Keep everything dry, including clothing, work area, cables, elec-

trode holder, and power supply. Fix water leaks immediately.

h. Refer to AWS Standard Z49.1 in Item 6 below for specific ground-

ing recommendations. Do not mistake the work lead for a ground

cable.

4. VENTILATION -- Fumes, particularly in confined spaces, can cause

discomfort and physical harm. Do not breathe fumes. Therefore:

a. At all times provide adequate ventilation in the work area by natu-

ral or mechanical ventilation means. Do not weld, cut, or gouge

on materials such as galvanized zinc, lead, beryllium, or cad-

mium unless positive mechanical ventilation is provided. Do not

breathe fumes from these materials.

b. Do not operate in locations close to chlorinated hydrocarbon

vapors coming from degreasing or spraying operations. The

heat or arc rays can react with solvent vapors to form phos-

gene, a highly toxic gas, and other irritant gases.

c. If you develop momentary eye, nose, or throat irritation, while

operating, this is an indication that ventilation is not adequate.

Stop work and take necessary steps to improve ventilation in

the work area. Do not continue to operate if physical discomfort

persists.

d. Refer to AWS Standard Z49.1 in Item 6 below for specific ventila-

tion recommendations.

5. EQUIPMENT MAINTENANCE -- Faulty or improperly maintained

equipment can result in poor work, but most importantly it can cause

physical injury or death through fires or electrical shock. There-

fore:

a. Always have qualified personnel perform the installation, trouble-

shooting, and maintenance work. Do not perform any electrical

work unless you are qualified to perform such work.

b. Before performing any maintenance work inside a power sup-

ply, disconnect the power supply from the electrical power

source.

c. Maintain cables, grounding wire, connections, power cord and

power supply in safe working order. Do not operate any equip-

ment in faulty condition.

d. Do not abuse any equipment or accessories. Keep equipment

away from heat sources such as furnaces, wet conditions such

as water puddles, oil or grease, corrosive atmospheres and in-

clement weather.

e. Keep all safety devices and cabinet covers in position and in

good repair.

f. Use equipment for its intended purpose. Do not modify it in any

manner.

6. ADDITIONAL SAFETY INFORMATION -- For more information on

safe practices for setting up and operating electric welding and

cutting equipment and on good working habits, ask for a free copy

of ESAB's "Precautions and Safe Practices for Electric Welding and

Cutting," Form 52-529. The following publications which are avail-

able from the American Welding Society, P.O. Box 351040, Miami,

FL 33135, are recommended to you:

a. "Safety in Welding and Cutting" - AWS Z49.1 (ANSI)

b. "Recommended Safe Practices for Gas-Shielded Arc Welding"

- AWS A6.1

c. "Recommended Safe Practices for the Preparation for Welding

and Cutting of Containers and Piping That Have Held Hazard-

ous Substances" AWS F4.1

d. "Recommended Safe Practices for Plasma Arc Cutting" - AWS

A6.3

e. "Recommended Safe Practices for Plasma Arc Welding: - AWS

C5.1

f. "Recommended Safe Practices for Air Carbon Arc Gouging and

Cutting" - AWS C5.3

F-14-260

tection to the rectifier SCR's and diodes. Protection for the

main transformer, bridge rectifier, and inductor is provided by

over-temperature thermal switches located in or on these com-

ponents. These switches interrupt power in the event of an

overload or overheating condition and automatically reset when

the components have cooled to their normal operating tem-

perature. Dynamic smoothing of the d.c. output current is

provided by an integrally-mounted, fixed inductor.

The solid state circuitry of the PHC-402 produces stable cur-

rent range and eliminates the "drift" in output of the power

supply as the control components heat up. In addition, this

control circuit has built-in line voltage compensation, which

corrects the output of the power supply for various changes in

the input line voltage. This feature ensures consistency in

cutting conditions even if line voltage changes. The Current

Control potentiometer, on the front panel, sets and regulates

the desired amount of output current for your operation. The

panel-faced dial provides a convenient reference for resetting

previously known conditions. Actual load current and volt-

age are indicated by an ammeter and voltmeter mounted on the

front panel.

Connections for control functions and auxiliary apparatus are

made from three-plug receptacles. Two three-pin receptacles

are connected in parallel and therefore can be used inter-

changeably for remote contactor operation or to parallel the

operation of two PHC-402's. The remaining eight-pin recep-

tacle provides connection for auxiliary 115-volts out, remote

current control and remote ammeter indication.

The power supply is designed for ease in moving and han-

dling. Sufficient clearance and reinforcement at its base per-

mits lifting with a fork-lift truck; or raising with a crane or hoist,

using the lifting rings in the top cover.

B. OUTPUT RATING/DUTY CYCLE

The PHC-402 has two output ratings: the 100% continuous

duty @ 400 amperes means that this rated load (400 amps) can

be applied continuously without a cool-down period; and a

100% duty-1/2 hour @ 500 amperes, which means that this

rated load (500 amps) can be applied continuously for 30 min-

utes and must then cool down (with fan motors running) for 30

minutes. Cooling periods would be proportionate with shorter

operating periods.

IMPORTANT: Output ratings are designed and based on

an unobstructed supply of clean (no conduc-

tive dust) cooling air flow over its internal

components. DO NOT USE FILTERS ON

THIS UNIT. Periodically blow out dirt accu-

mulations, using low pressure air.

II. INSTALLATION

Proper installation can contribute materially to the satisfactory

and trouble-free operation of the power supply. It is sug-

gested that each step in this section be studied carefully and

followed as closely as possible.

A. UNCRATING THE POWER SUPPLY

Immediately upon receipt of the power supply, it should be

inspected for damage which may have occurred in transit.

Notify the carrier of any defects or damage at once.

Carefully remove the power supply from the shipping con-

tainer. Do not use any lever device which might damage the

unit. Check the container for any loose parts which might

otherwise be lost. Remove all packing materials and make sure

that the passages for cooling air are not obstructed. Check

the contents against the packing list for shortages.

If the unit is not to be installed immediately, store it in a clean,

dry, well ventilated area.

B. LOCATION

The location of the power supply should be carefully selected

to ensure satisfactory and dependable service.

The power supply components are maintained at proper oper-

ating temperatures by forced air which is drawn through the

cabinet by the fan unit. For this reason, it is important that the

power supply be located in an indoor-open area where air can

circulate freely at the front, bottom and rear openings of the

cabinet. If space is at a premium, leave at least 2 feet of clear-

ance at the rear of the cabinet. The location should be such

that a minimum of dirt, dust or moisture will be drawn into the

air stream. It is also desirable to locate the unit so that the

cover can be removed easily for cleaning and troubleshooting.

C. PRIMARY ELECTRICAL INPUT CONNECTIONS

Precautionary measures should be taken to provide

maximum protection against electrical shock. When

electrical connections are made from the power sup-

ply to the main line disconnect switch, be sure that

all power is off by opening the line disconnect switch.

This power supply is a three-phase unit and must be con-

nected to a three-phase power line. Although designed with

line voltage compensation, it is suggested the unit be oper-

ated on a separate circuit to assure the performance of the

machine is not impaired due to an overloaded circuit.

1. A line (wall) disconnect switch, with fuses or circuit break-

ers, should be provided at the main power panel (see Fig.

1). The primary power leads should include three power

leads and one ground wire. The wires may be heavy rubber

covered cable, or may be run in a solid or flexible conduit.

Refer to the following table for recommended input con-

ductors and line fuse sizes.

Recommended Sizes for Input Conductors

and Line Fuses

Rated

Output

Rated Input

Voltage/Fre Amps

Input

Cond.*

CU/AWG

Grd

Wire*

CU/AWG

Fuse

Size

Amps

400

Amp

460V., 60 Hz.

415V., 50 Hz.

380V., 50 Hz

130

144

158

1/0

2/0

200

225

250

500

Amp

460V., 60 Hz.

415V., 50 Hz.

380V., 50 Hz.

163

180

198

2/0

3/0

250

300

*Sized per National Electric Code for 75° C rated copper

conductors @ 30° C ambient. Not more than three

conductors in raceway or cable. Local codes should be

followed if they specify sizes other than those listed above.

2. For access to primary power input connections on main

contactor and chassis ground connection remove power

supply right side panel.

3. Thread the input conductor cable from the wall disconnect

switch through the 3-1/2-in. dia. access hole in the rear

panel of the power supply. Secure the input cable with a

customer-supplied strain relief or conduit coupling, then

connect the primary power leads to terminals L1, L2, and L3

of the main contactor as shown in Fig. 1. Also connect the

ground wire to the stud provided on the chassis base in-

side the right-rear of the cabinet.

CAUTION: It is of the utmost importance that the chassis

be connected to an approved electrical

ground to prevent accidental shocking.

4. The primary windings of the main transformer (MTR) and

the primary of the control transformer (CTR) are tapped to

allow reconnection for different primary input voltages. As

shipped from the factory, the power supply is wired for a

460 volt, 60 Hz. input.

To reconnect the unit for a 380 or 415 volt, 50 Hz. input

the following wiring modifications must be made (also re-

fer to schematic and wiring diagrams):

a. Locate the No. 2 AWG insulated cables which connect

the main transformer primary taps MTR-A-H1 to -H4,

MTR-B-H1 to -H4, and MTR-C-H1 to -H4 -- these con-

nections provide the 460 volt, 60 hertz input.

b. Next, locate the H3 and H2 alternate input bus taps on

the face of each primary coil MTR-A, -B, and -C. The

H3 taps provide the connections for a 415 volt, 50 hertz

input, and the H2 taps provide the connections for a

380 volt, 50 hertz input.

c. To change to either the 415 or 380 volt input, you sim-

ply unbolt the 460 volt cable connections on the H4

taps (described in "a" above); and using the same hard-

ware, reconnect the loose end of the cables as follows:

(i) For 415 volt, 50 hertz input, connect:

MTR-A-H1 cable to bus tap MTR-A-H3,

MTR-B-H1 cable to bus tap MTR-B-H3,

MTR-C-H1 cable to bus tap MTR-C-H3.

(ii) For 380 volt, 50 hertz input, connect:

MTR-A-H1 cable to bus tap MTR-A-H2,

MTR-B-H1 cable to bus tap MTR-B-H2,

MTR-C-H1 cable to bus tap MTR-C-H2.

d. To complete the input voltage wiring modifications,

you must also reconnect the control transformer

(CTR). Locate the brown wire (coming from main

contactor) which connects 460 volts from MC-L1 to

the CTR-H9. To change voltages, disconnect this

brown wire from CTR-H9 and reconnect as follows:

MC-L1 to CTR-H6 for 415 volt input, or MC-L1 to CTR-

H5 for 380 volt input.

5. Recheck all connections to make sure that they are tight,

well insulated, and that the proper connection has been

made.

D. SECONDARY ELECTRICAL OUTPUT CONNECTIONS

Before making any connections to the power supply output

busbars, make sure that the power supply is deenergized. To

be doubly safe, check the output busbars (POS. and NEG.) with

a voltmeter to make sure all power is OFF.

For access to the PHC-402 output voltage busbar/cutting lead

connections and nozzle (pilot arc ground) connection, remove

the left side panel of the power supply.

1. Select the output cables on the basis of one 4/0 AWG, 600

volt insulated copper cable for each 400 amperes of output

current. Do not use ordinary welding cable. Bring these

cables through the large openings provided at the bottom

of the front panel and connect them to the two busbar

terminals mounted in the unit using UL listed pressure wire

connectors (refer to schematic diagram and Figure 1). Each

busbar terminal is labeled with a decal to help facilitate the

basic plasma arc hookup (negative bus to torch electrode

and positive bus to the workpiece).

2. If parallel operation of two units is to be used, consult with

the factory.

3. Make the "Pilot Arc Work" connection between the power

supply bridge assembly and plumbing box using a high

voltage (15,000 v.) Pilot Arc Work Wire (10-ft.) P/N 994065

supplied as part of the PCM-500 Cutting Outfit (also refer

to note in Fig. 1). The Pilot Arc stud connection is adjacent

to the PILOT ARC WORK decal positioned on the left side

F-14-260

of the bridge heat sink (see Fig. l). Earlier models contained

a decal identifying this connection as "NOZZLE."

CAUTION: Do not make the "pilot arc work" connec-

tion at any other place. Making the connec-

tion elsewhere will cause the pilot arc cur-

rent to pass through the shunt, and the power

supply will mistake the pilot arc current for

main arc current. The result will be arc cur-

rent instability during arc starting which can

result in short nozzle and electrode life.

E. CONTROL CONNECTIONS

All control functions are provided from three receptacles lo-

cated on the power supply's front panel. (Refer to schematic

diagram for proper terminations, and to Figure 1 for location.)

Connections to a remote welding or cutting control assembly

are provided through the 8-pin receptacle (P4), marked "Re-

mote Control." When used, this receptacle supplies 10 am-

peres of 115-volt a.c. control power for auxiliary apparatus,

remote current control, and connections for remote ammeter

indication.

The two 3-pin receptacles (P3 and P5) marked "Contactor" are

internally connected in parallel and are used for remote

contactor operation. Either of the 3-pin receptacles may be

used to energize the power supply's main contactor from a

remote control station. The remaining receptacle can then be

used to connect to one of the two 3-pin receptacles on a sec-

ond unit if parallel operation of two units is desired. In this

manner, the main contactor in both units can be actuated from

one remote control source at the same time. An optional 8-foot

interconnecting cable assembly, P/N 993963, with a 3-pin plug

on each end is available for this purpose.

III. OPERATION

CAUTION: Never, under any circumstances, operate the

power supply with cover or side panels re-

moved. In addition to the safety hazard, im-

proper cooling may cause damage to inter-

nal components. Also make sure you are

adequately protected before you start cut-

ting -- welders helmet, gloves and ear pro-

tection should always be worn.

The current potentiometer indicator dial located on the power

supply front panel primarily serves as a handy reference for

presetting known load conditions that have been derived

through previous operating experience. The accuracy of these

approximated settings can be affected by arc voltage, or the

voltage drop in the secondary output cables. Final current

adjustment of the unit should always be obtained by utilizing

the meters.

A. CUTTING CONTROLS AND SEQUENCE OF OPERATION

The power supply controls and their functions are described

in the operating sequence below:

1. Make the secondary output connections to the positive

and negative output busbar terminals as explained in Sec-

tion II-D.

Fig. 1 - Interconnection Diagram

4. The main or cutting arc will transfer to the work. The cur-

rent detector circuit located on the p.c. board senses the

transferred arc and stabilizes the output current at the pre-

set value in approximately 0.1 seconds after the main arc

transfer. The boost supply shuts off during the 0.1 second

stabilization period. It is "on" only to provide the 415 volts

open circuit voltage for starting.

5. The PHC-402 can be shut down either of two ways:

a. Depress the Cut Stop button in the remote control --

this automatically deenergizes the main contactor coil

in the power supply. When this occurs, the solid state

logic in the 402 turns off the main current supply before

the main contactor physically opens. This feature helps

to preserve the main contactor contacts by not open-

ing them under load.

b. When the arc is broken. When the torch runs off the

workpiece, the main arc will break (extinguish). This

arc outage will automatically be detected by the PHC-

402's current detector circuit which reactivates the boost

supply and provides 415 v.d.c. across the output termi-

nals. The power supply is now "ready" for restarts.

Proper grounding procedures must be adhered to

particularly in the case of plasma power supplies.

Therefore, we are reprinting below the paragraph

on proper grounding covered in the American Weld-

ing Society Booklet, "Safety in Welding and Cutting"

(AWS Z49.1) which states:

4.3.2.2 Grounding the Work. The work or metal upon

which the welder welds shall be grounded to a good

electrical ground.

Note 1: Grounding can bed done by locating the work on a

grounded metal floor or platen or by connection to a grounded

building frame or other satisfactory ground. Alternatively it

may be done by grounding the work lead at or near the weld-

ing machine. Care should be taken, however, to avoid double

grounding as otherwise the welding or cutting current may

flow through a connection intended only for safety ground-

ing and may be of higher magnitude than the grounding con-

ductor can safety carry. Special radio-frequency grounding

is advisable for equipment using high-frequency arc stabiliz-

ers. (See Recommended Installation and Test Procedures of

High Frequency Stabilized Arc Welders, 1970, National Elec-

trical Manufacturers Association.

IV. MAINTENANCE

If this equipment does not operate properly, stop

work immediately and investigate the cause of the

malfunction. Maintenance work must be performed

by an experienced person, and electrical work by a

trained electrician. Do not permit untrained persons

2. Make the control connections as explained in Section II-E.

3. Determine the current control mode the power supply is to

be operated in and set the Remote Control Switch to the

desired position. With this switch in the "Panel" position,

output current is controlled by setting the power supply

current control potentiometer. When the PHC-402 is inter-

connected with a cutting control assembly, place this switch

in the "Remote" position to allow current adjustment from

the cutting control.*

4. If the primary electrical input connections to the power

supply have been correctly installed, as explained in Sec-

tion II-C, close the main line (wall) disconnect switch. Power

will be applied to the fan motor and the Pilot Light (PL) on

the front panel will glow.

5. Adjust either the PHC-402 or the remote cutting control

Current Potentiometer (CCP) for the approximate desired

output current. (Suggested initial settings for PT-500

torches with high current nozzles would be 6 or greater on

the dial, and around 4 for torches using standard nozzles

under 300 amperes. The "7" dial setting is about 400 am-

peres.) Fine adjustment of the output current may be made

by varying the setting of these controls. The range through

which the output current can be controlled is shown in the

specification table.

6. Operate the starting switches on the cutting control to en-

ergize the power supply main contactor. Voltage will ap-

pear at the power supply output busbar terminals.

7. After cutting has begun, observe the ammeter, voltmeter,

and/or the cutting operation. If necessary, readjust the

current control as required.

8. The cutting arc will extinguish and the power supply will

shut down, either automatically when the torch runs past

the workpiece, or when the remote control Cut Stop button

is depressed.

*NOTE: When the PHC-402 is interconnected with older

versions of the PCC-8 Cutting Control (part of

PCM-8 outfit, F-12-528), the "Up-Down" switch

in the control must be replaced with any value

from 2 to 20 K ohm (+/-20%), 2.25 W potentiom-

eter to allow current adjustment from the control.

B. OPERATION

A properly installed and operating PHC-402 should function

as follows:

1. After energizing the PHC-402 (at the wall disconnect

switch), the Main Power light (on the front panel) and the

fan motor will operate.

2. When the cutting control (Cut Start) is energized; the power

supply main contactor will close and power is applied to

the main transformer, boost bridge supply and 415 volts

open circuit is available at the power supply output termi-

nals as indicated on the voltmeter.

3. After gas preflow period, the high frequency (in the cutting

control plumbing box) will energize and the pilot arc will

start.

F-14-260

to inspect, clean, or repair this equipment. Use only

recommended replacement parts.

To prevent accidental electrical shock, be sure that

the wall disconnect switch or circuit breaker is open

before attempting any inspection or work on the in-

side of the power supply.

A. CLEANING

Since there are no moving parts (other than the fan) in the

power supply, maintenance consists mainly of keeping the

interior of the cabinet clean. Periodically, remove the cover

from the cabinet and blow accumulated dust and dirt from the

air passages and the interior components, using clean low

pressure air. It is imperative that the air passages, to the inte-

rior of the unit, be kept free of dirt accumulation to ensure

adequate circulation of cooling air, especially over the rectifier

bridge plates. This unit is NOT designed to be used with air

filters of any kind. Any obstruction to the free flow of cooling

air will damage the machine and void the warranty. The length

of time between cleaning will depend on the location of the

unit, and the amount of dust in the atmosphere.

B. LUBRICATION

Fan motor with oil tubes located on the side of the motor re-

quire lubrication after 1 year of service. Motor without oil

tubes are permanently lubricated for life and should not re-

quire any attention.

C. TESTING AND REPLACING BRIDGE ASSEMBLY COMPO-

NENTS

The silicon diodes and silicon controlled rectifiers used in this

power supply are devices which allow current flow in only one

direction, and they block current flow in the other direction.

These components are designed to provide long trouble-free

operation; however should a failure occur, they may require

replacement. The location and replacement parts data for the

diodes and SCR's are shown in Figs. 5 and 6.

If after troubleshooting, the "trouble symptom" appears to be

in the bridge (BR, BBR) network, the following three part pro-

cedure -- Visual Analysis, Component Group Testing and Indi-

vidual Component/Isolation Testing -- can be used to deter-

mine the faulty component(s).

If component repair or replacement is necessary, the Boost

Bridge components are readily accessible in the power sup-

ply; however, to service Main Bridge components, removing

the bridge assembly is recommended.

CAUTION: Before removing the main bridge assembly

for servicing, carefully tag (identify) all in-

terconnecting wires and bus connections to

facilitate proper reinstallation -- also refer

to the diagrams and illustrations in the back

of this booklet.

1. Visual Analysis for Defective BR/BBR Components

a. Remove top and left side panels of power supply. In-

spect the 500 amp. BR fuse links (F3 and F4) mounted

in the Main Transformer secondary bus bars to see if

they are blown open. If not, check the 30 amp. BBR

cartridge fuses (F1 and F2) with an ohmmeter to deter-

mine if they are open.

b. If either or both of the fuses protecting its respective

bridge assembly are open, it's a sign that one or more of

the diodes or SCR's in that particular bridge may be

shorted.

c. Also check for cracked or broken ceramic around each

diode pigtail or SCR body -- if cracked, its a sign of a

shorted diode or SCR. When the larger diodes or SCR's

fail, they most commonly fail shorted.

2. Testing Main Bridge Rectifier Assembly

The main bridge essentially contains three groups of com-

ponents to be tested: Power Diodes D4, D5 and D6; Free-

wheeling Diode D7; and SCR's 4, 5 and 6. The group test-

ing sequence does not require electrical isolation; how-

ever, to determine the specific faulty component in a group,

some form of isolation may be required as noted by the

following:

a. Checking Power Diode Group D4, D5 and D6.

(1) If fuse links F3 and F4 are not blown, use an ohm-

meter set to its lowest resistance scale and check

the diode group as described in step a-(3). Check-

ing any one diode within the group will determine

if the group is good or if a shorted condition ex-

ists. If there is a short, you must electrically iso-

late to determine the specific component - see

step a-(4).

(2) If one or more fuse links (F3/F4) are blown, the

diodes must be isolated and checked individu-

ally -- see step a-(4).

(3) Ohmmeter check of diodes (group or individual).

(a) Place one test probe on Negative Heatsink

(diode stud) and touch the other probe to

the diode pigtail and note the resistance read-

ings obtained (high or low).

(b) Reverse the test probes and repeat the check

and note the resistance readings obtained

(exactly opposite of the first reading).

rection and low in the opposite direction.

Diodes are bad if the resistance readings are

low in both directions. High readings in both

directions when using a digital ohmmeter

indicates a good diode.

(4) If the diagnosis indicates a defective diode within

the group, you must disconnect each diode pig-

tail to electrically isolate it and repeat the ohmme-

ter tests in step a-(3-a), -(3-b), -(3-c) to each di-

ode.

b. Checking the Freewheeling Diode D7.

This diode must be checked in the circuit using the

same procedures outlined in step a-(1), -(2) and -(3). If

the diode tests good, nothing else must be done; how-

ever, if the diode tests bad, you must disconnect its

pigtail and retest it for verification.

c. Check the SCR's Group SCR 4, 5 and 6.

NOTE: Before proceeding with the following SCR

tests, all diodes D4, 5, 6 and 7 should have

been checked, and defective (shorted) diodes

electrically isolated.

(1) If fuse links F3 and F4 are not blown and still

connected to the bridge heatsink, use an ohmme-

ter set to its lowest resistance scale and check

the SCR group as described in step C-(3). Check-

ing any one SCR within the group will determine

if the group is good or if a shorted condition ex-

ists. If there is a short, you must electrically iso-

late to determine the specific faulty component,

see step c-(4).

(2) If one or more fuse links (F3/F4) are blown, the

SCR's must be isolated and checked individually

-- see step c-(4).

(3) Ohmmeter check of SCR's (group or individual).

(a) Place one test probe on the POS. heatsink

(same as the shunt) and touch the other test

probe to each of the SCR's anode heatsinks.

The resistance reading across each SCR

should be 1000 (1K) ohms or higher.

(b) Reverse the test probes and repeat the

check. Again, the resistance reading across

each SCR should be 1000 (1K) ohms or

higher.

resistance reading in either direction.

(4) If the diagnosis indicates a defective SCR within

the group, you must disconnect fuses F3 and F4

to electrically isolate the SCR's (assuming all di-

odes D4, 5, 6, 7 have checked good, or defective

diodes previously isolated), and repeat the ohm-

meter tests in step c-(3-a), -(3-b), -(3-c) to each

SCR.

3. Testing Boost Bridge Rectifier Assembly.

a. Remove the 30 ampere fuses, F1 and F2, to electrically

isolate the BBR assembly. (It's always good practice to

check the fuses for continuity to make sure whether

they are good or bad. Use ohmmeter set to RX1 scale.)

b. Check the diodes (D1, 2 and 3) with an ohmmeter set to

the RX1 scale, as follows:

NOTE: The following ohmmeter readings are shown using

a Simpson 260 meter. When using a Digital or some

Analog meters, you may have to use a higher resis-

tance scale. The actual number obtained is not im-

portant, so long as there is a substantial difference

between the forward and reverse readings.

(1) Place one test probe on the NEG. (diode stud)

Heatsink and touch the other probe to each di-

ode pigtail's SCR Heatsink. Note the resistance

reading obtained. All three readings should be

similar (high or low).

(2) Reverse the test probes and recheck the diodes.

Note each resistance reading. All three readings

should be similar; but, exactly opposite of those

noted in the first reading.

(3) Diodes are good when they show low resistance

(3 to 5 ohms) in one direction, and high resis-

tance (2K ohms or higher) in the opposite direc-

tion.

(4) Diodes are bad when they show no, or very low,

resistance in both directions -- shorted; or if they

show very high resistance in both directions --

open.

c. Check the SCR's (SCR1, 2 and 3) with an ohmmeter set

to RX1 on the RX100 scale, as follows:

(1) Place one test probe on the POS. (SCR pigtails)

Heatsink and touch the other probe to each SCR's

stud heatsink. All three readings should show a

high resistance of 1000 (1K) ohms or higher.

(2) Reverse the test probes and recheck the SCR's.

Again, all three readings should show a high

resistance similar to the first test.

(3) An SCR is bad, if it shows no, or very low (less

than 1 ohm) resistance in either direction.

4. Replacing Faulty SCR's and Diodes.

a. Make sure that heatsink mounting surfaces are cleaned

before replacing faulty components.

b. For diodes and SCR's, coat mounting surfaces with

Alcoa No. 2 EJC Electrical Joint Compound, available

from ESAB in 8 oz. containers under P/N 73585002.

c. Clamping procedure for Main Bridge SCR's (4, 5 and 6).

(1) Tighten the SCR clamp nuts by hand until

fingertight.

(2) Then, using a wrench, alternately tighten each

nut 1/4 turn at a time until the "spring indicator"

on the clamp assembly shows slightly more than

1000 pounds, or 1 on the indicator.

d. Torque procedures for remaining SCR's and diodes.

(1) Use a torque wrench to tighten stud mounted

SCR's and diodes. Recommended torques are on

the following table.

(2) If a torque wrench is not available, care should be

taken that the (stud) nuts are tightened only until

firm.

F-14-260

Recommended Torques

Main Bridge Diodes

D4, 5, 6, & 7

Min., 275 in.-lbs. (23 ft.-lbs.)

Max., 325 in.-lbs. (27 ft.-lbs.)

Boost Bridge Diodes

D1, 2, 3

Min., 20 in.-lbs. (1.7 ft.-lbs.)

Max., 30 in.-lbs. (2.5 ft.-lbs.)

Boost Bridge SCR’s

SCR1, 2, 3

Min., 125 in.-lbs. (10.4 ft.-lbs.)

Max., 150 in.-lbs. (12.5 ft.-lbs.)

V. TROUBLESHOOTING

Be sure that the wall disconnect switch or circuit

breaker is open before attempting any inspection or

work on the inside of the power supply.

If the power supply is operating improperly, the following

troubleshooting information may be used to locate the source

of the trouble.

Check the problem against the symptoms in the following

troubleshooting guide. The remedy for the problem may be

quite simple. If the cause cannot be quickly located, open up

the unit and perform a simple visual inspection of all the com-

ponents and wiring. Check for proper terminal connections,

loose or burned wiring or components, blown fuses, bulged or

leaking capacitors, or any other sign of damage or discolora-

tion.

TROUBLESHOOTING GUIDE

A. Fan Not Running

1. No input power. Check main line (customer's) switch fuses.

2. Defective control transformer. Check for continuity.

3. Fan motor defective. Check motor and leads, and replace if

necessary.

B. No Output

1. No incoming three-phase power, wall disconnect switch

may be open, or fuse(s) blown.

2. Poor connections at output terminals, tighten or replace

connections.

3. Main contactor not energized.

a. Thermal overload (TTS1, 2, 3, ITS or BTS) device(s)

tripped.

b. Contactor coil defective, or not receiving 120 volt power

through contactor plug(s) P3/P5 pins A and B.

c. Defective or missing p.c. board.

C. Low Open Circuit Voltage (O.C.V.)

General -- normal O.C.V. is 415 volts for a nominal 460 volt line

input. If your actual line voltage is running lower; your O.C.V.

will be proportionately lower, if it's running higher, the O.C.V.

will be proportionately higher. Regardless of the range, so

long as O.C.V. is available it means that the main contactor

(MC) is energized. However, if the voltage is in the range of

250 volts, it's a sign that you're only receiving your open cir-

cuit voltage from the main bridge rectifier. This indicates that

for one reason or another, the boost bridge rectifier is not

supplying 415 volts.

1. Boost bridge fuses F1 and/or F2 blown. (Fuse replacement

specifications are critical -- only use 30 ampere, 250 volt,

slo-blo or time-delay fuses; such as, Buss No. FNW30,

Shawmut No. TRM30, or Factory replacements.)

2. Faulty SCR's or diodes in boost bridge assembly, check per

Section IV-C-1 and -3.

3. P.C. board defective. Replace board.

D. No Current Control or Erratic Output Current

1. No current control -- none at all, fixed, or all out.

a. Missing power or blown fuse links.

b. Defective pc board.

c. Overheating or defective SCRs in main bridge.

d. If current is fixed at around 500-600 amps, the bottom

of the current control pot. (CCP) may not be connected,

and this results in feeding +10 volts straight into the pc

board.

2. Erratic current control.

a. Defective current potentiometer (CCP), panel and/or

remote location.

b. Defective remote control switch (RCS), check continu-

ity.

c. A defective or intermittent connection in P4 (remote

control receptacle) connecting the bottom of CCP back

to common.

d. Pilot Arc Work connection not properly made -- see

Section II-D-3 and Fig. 1.

E. Limited Output Current

1. Single phasing resulting from blown fused link(s) F3 and/

or F4, and/or defective SCR(s) or diodes in main bridge.

Check per Section IV-C-1, -2 and -4.

2. Defective pc board, that's not gating one of the main bridge

SCR's.

3. Defective current control potentiometer (CCP).

F. Short (Torch) Tip Life -- Double Arcing

1. Low open circuit voltage, see symptom C.

2. Defective pc board.

3. Defective SCR in Main Bridge.

4. Pilot Arc Work connection not properly made -- see Sec-

tion II-D-3 and Fig. 1.

VI. REPLACEMENT PARTS DATA

1. All replacement parts are keyed on the illustrations which follow. Order replacement parts by number

and part name, as shown on illustrations. DO NOT ORDER BY PART NUMBER ALONE.

2. Many of the parts on the illustrations, particularly electronic parts, are 'vendor items.' This means that

they are standard commercial parts made by and purchased from other manufacturers. If you order from

these outside sources, use the manufacturer's part number or designation as shown in the Electrical

Parts List.

3. Always state the series or serial number of the machine on which the parts are to be used. The serial

number is stamped on the unit nameplate.

4. Indicate any special shipping instructions.

5. Order replacement parts from the ESAB Customer Service Dept. - Florence, SC or ESAB Welding Equip-

ment Distributor nearest you.

Fig. 2 - PHC-402, Front View

F-14-260

Fig. 4 - PHC-402, Right Side View

Fig. 3 - PHC-402, Left Side View

Fig. 5 - Boost Bridge Assembly, P/N 679508

F-14-260

Fig. 6 - Main Bridge (BR) Rectifier Assembly, P/N 679507

Fig. 7 - Schematic Diagram, PHC-402

F-14-260

Fig. 8 - Wiring Diagram, PHC-402, (Sht. 1 of 2)

Fig. 9 - Wiring Diagram, PHC-402 (Sht. 2 of 2)

F-14-260 2/95 Printed in U.S.A.

ESAB Welding & Cutting Products

PO Box 100545 Florence SC 29501-0545

ESAB PHC-402 Cutting Power Supply Troubleshooting instruction

Brand: ESAB

Model: PHC-402 Cutting Power Supply

Category: Welding System

Type: Troubleshooting instruction

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ESAB PHC-402 Cutting Power Supply Troubleshooting instruction

ESAB PHC-402 Cutting Power Supply Troubleshooting instruction

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