PCM-875
PLASMA CUTTING
CONSOLE/POWER SOURCES
with CE Compliances
230 V, 50 Hz, 3-Phase
400 V, 50 Hz, 3-Phase
Service Manual
558000-892 0202
WARNING
ARC WELDING AND CUTTING CAN BE INJURIOUS TO YOURSELF AND OTHERS. TAKE PRECAUTIONS WHEN WELDING. ASK FOR YOUR EMPLOYER’S SAFETY PRACTICES WHICH SHOULD
BE BASED ON MANUFACTURERS’ HAZARD DATA.
ELECTRIC SHOCK - Can kill
l Install and earth the welding unit in accordance with applicable standards.
l Do not touch live electrical parts or electrodes with bare skin, wet gloves or wet clothing.
l Insulate yourself from earth and the workpiece.
l Ensure your working stance is safe.
FUMES AND GASES - Can be dangerous to health
l Keep your head out of the fumes
l Use ventilation, extraction at the arc, or both, to keep fumes and gases from your breathing zone
and the general area.
ARC RAYS - Can injure eyes and burn skin.
l Protect your eyes and body. Use the correct welding screen and filter lens and wear protective
clothing.
l Protect bystanders with suitable screens or curtains.
FIRE HAZARD
l Sparks (spatter) can cause fire. Make sure therefore that there are no inflammable materials nearby.
NOISE - Excessive noise can damage hearing
l Protect your ears. Use ear defenders or other hearing protection
l Warn bystanders of the risk.
MALFUNCTION - Call for expert assistance in the event of malfunction.
READ AND UNDERSTAND THE INSTRUCTION MANUAL BEFORE INSTALLING OR OPERATING.
PROTECT YOURSELF AND OTHERS!
TABLE OF CONTENTS
SECTION 1 SPECIFICATIONS ............................................................................................................ 3
SECTION 2 MAINTENANCE................................................................................................................ 4
General, Inspection and Cleaning, PT-27 Torch
Consumable Parts, Flow Switch, IGBT
Handling & Replacement
SECTION 3 TROUBLESHOOTING...................................................................................................... 6
Troubleshooting, Troubleshooting Guide,
Reference Voltage Checks, Sequence of
Operation, Schematic and Wiring Diagrams
SECTION 4 REPLACEMENT PARTS ................................................................................................ 19
Maintenance and Repair work should be performed by an experienced person, and
electrical work only by a trained electrician. Do not permit untrained persons to
inspect, clean, or repair equipment. Use only recommended replacement parts.
For installation and operation instructions, see 558000-880 (F-15-418).
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SECTION 1 SPECIFICATIONS
PCM-875 Specifications
Rated 60% Duty Cycle* 60 A @ 120 V dc
Output 100% Duty Cycle* 50 A @ 120 V dc
Output Current Range 10 to 60 Amperes
Open Circuit Voltage 275 V dc
Rated Primary Input 220 V ac, 50/60 Hz, 3-phase 24 A/phase
@ 7.2 kW Max. Output Power 400 V ac, 50/60 Hz, 3-phase 13 A/phase
60 A @ 120 Vdc
Power Factor @ 60 Amperes Output 90% (220 V, 3-phase)
92% (400 V, 3-phase)
Efficiency @ 60 Amperes Output 90% Typical
Current Capacity PT-27 80 A DCSP
Air Requirements PT-27 150 l/min @ 4.5 - 5.2 bar
Dimensions Length 516 mm
Height 409 mm
w/handles 465 mm
Width
w/o opt. storage 275 mm
w/opt. torch storage 333 mm
Weight of PCM-875 System 39.5 kg
Shipping Weight 45.4 kg
* Duty cycle is based on a 10-minute period; therefore, a 60-percent duty cycle means the power source may operate for 6 minutes with a cool
down period of 4 minutes and a 100-percent duty cycle means the power source may operate continuously.
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SECTION 2 MAINTENANCE
2.1 GENERAL
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 to inspect,
clean, or repair this equipment. Use only recommended
replacement parts.
Be sure that the wall disconnect switch or wall circuit breaker is open before attempting any inspection or work inside of the PCM-875.
2.2 INSPECTION AND CLEANING
Frequent inspection and cleaning of the PCM-875 is
recommended for safety and proper operation. Some
suggestions for inspecting and cleaning are as follows:
A. Check work cable for secured connection to
workpiece.
B. Check safety earth ground at workpiece and at
power source chassis.
C. Check heat shield on torch. It should be replaced
if damaged.
D. Check the torch electrode and cutting nozzle for
wear on a daily basis. Remove spatter or replace
if necessary.
E. Make sure cable and hoses are not damaged or
kinked.
F. Make sure all plugs, fittings, and ground connec-
tions are tight.
G. With all input power disconnected, and wearing
proper eye and face protection, blow out the inside of the PCM-875 using low-pressure dry compressed air.
The PT-27 torch head contains a gas flow check
valve that acts in conjunction with the flow switch
and circuitry within the power source. This system prevents the torch from being energized with
high voltage if the torch switch is accidentally
closed when the shield is removed. Always replace
torch with the proper torch manufactured by ESAB
since it alone contains ESAB¹s patented safety interlock.
To assemble the consumable parts, refer to Figure 2-1.
A. Place nozzle, swirl baffle and electrode into the
shield as shown.
B. Thread assembly to the torch body and hand tighten.
Always make sure the shield is very tight before
cutting.
ELECTRODE
SWIRL BAFFLE
NOZZLE
SHIELD
Water or oil occasionally accumulates in compressed air lines. Be sure to direct the first blast
of air away from the equipment to avoid damage
to the PCM-875.
H. Occasionally, bleed all water from the filter beneath
the air filter-regulator.
2.3 PT-27 TORCH CONSUMABLE PARTS
Make sure power switch on PCM-875 is in OFF position before working on the torch.
IMPORTANT!
MAKE SHIELD VERY TIGHT!
Figure 2-1. Assembly of PT-27 Torch Front End Parts
4
SECTION 2 MAINTENANCE
2.4 FLOW SWITCH (FIGURE 2-2)
When excessive contamination is found in the air, the
flow switch (FS-4) should be disassembled and cleaned
as follows:
A. Ensure the system is shut down and there is no
trapped air under pressure in the piping.
B. Remove the piston plug.
C. Remove the spring. Use care when handling spring
to prevent distortion.
D. Remove the piston.
E. Clean all parts with cleaning agent.
NOTE
Ensure cleaning agent does not contain solvents
which can degrade polysulfone. Warm water and
detergent is recommended for cleaning. Allow all
parts to dry thoroughly before reassembly.
Reassemble the flow switch in reverse order.
PISTON PLUG
SPRING
PISTON
FLOW SWITCH
• Use grounded work station with grounded floors
and grounded wrist straps when handling devices.
• Use a 100W resistor in series with the gate when
performing curve tracer tests.
• Never install devices into systems with power connected to the system.
• Use soldering irons with grounded tips when soldering to gate terminals.
When mounting IGBT modules on a heatsink, certain
precautions should be taken to prevent any damage
against a sudden torque. If a sudden torque (“one-sided
tightening”) is applied at only one mounting terminal
the ceramic insulation plate or silicon chip inside the
module may get damaged.
The mounting screws are to be fastened in the order
shown in Figure 2-3. Also, care must be taken to
achieve maximum contact (i.e. minimum contact thermal resistance) for the best heat dissipation.
Application of a thermal pad on the contact surface
improves its thermal conductivity. See Replacement
Parts section for the required pad.
A torque wrench should be used. Tighten mounting
screws to 32 kg-cm; wire connecting screws to 22 kgcm. If torque is too heavy, the device can damage like
the above “one-sided tightening”.
Two-Point Mounting Type
Temporary tightening è
Final tightening è
Figure 2-2. Disassembly / Assembly of Flow Switch
2.5 IGBT HANDLING & REPLACEMENT
Since IGBT gates are insulated from any other conducting region, care should be taken to prevent static
build up, which could possibly damage gate oxides. All
IGBT modules are shipped from the factory with conductive foam contacting the gate and emmiter sense
pins.
Always ground parts touching gate pins during installation. In general, standard ESD precautlions application to FETs should be followed.
Other handling precautions that should also be observed are as follows:
Four-Point Mounting Type
Temporary tightening èèè
Final tightening èèè
Figure 2-3. Screw Fastening Order
5
SECTION 3 TROUBLESHOOTING
3.1Troubleshooting
ELECTRIC SHOCK CAN KILL! Be sure that all
primary power to the machine has been externally
disconnected. Open the line (wall) disconnect switch
or circuit breaker before attempting inspection or
work inside of the power source.
Check the problem against the symptoms in the
following troubleshooting guide. The remedy may be
quite simple. If the cause cannot be quickly located,
shut off the input power, open up the unit, and perform a
simple visual inspection of all the components and wiring. Check for secure terminal connections, loose or
burned wiring or components, bulged or leaking capacitors, or any other sign of damage or discoloration.
3.2TROUBLESHOOTING GUIDE
The cause of control malfunctions can be found by
referring to the sequence of operations and electrical
schematic diagram (Figure 3-1 or 3-3) and checking
the various components. A volt-ohmmeter will be necessary for some of these checks.
Voltages in plasma cutting equipment are high
enough to cause serious injury or possibly death.
Be particularly careful around equipment when the
covers are removed.
NOTE
Before checking voltages in the circuit, disconnect the
power from the high frequency generator to avoid damaging your voltmeter.
A. Power Light (PL1) does not come on.
1. Visually inspect the machine for any damage.
2. Check if the cooling fan is running. If not, then check the following :
a. Check if the machine power cord is plugged to the input power receptacle.
b. Measure the input power at the receptacle. If not present, then check the wall
disconnect switch and it’s fuses.
c. Check Fuse (F1). If fuse is ok, then check the input circuit breaker (CB1) for proper operation. Replace
if defective.
3. If above items check OK , the problem is internal. Send unit to an Authorized Repair Station for repair.
a. If the cooling fan is running, then measure voltage between pins P2-11 and P2-14 of the control
board (should be 115 VAC). If there is no voltage, then replace transformer T2.
b. If the voltage is present, then the pilot light may be defective.
B. No Air Flow
A. Check air inlet supply. Unit requires 150 l/min at 4.5 bars.
B. Check air hose and connections. Tighten if leaking.
C. Does air flow when “air test” switch is in test position?
a. If not, check torch consumables, replace if necessary.
b. If above items check OK , the problem is internal. Take unit to an Authorized Repair Station for repair.
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SECTION 3 TROUBLESHOOTING
C. The Power light is on, but nothing happens when the torch switch is depressed. Fault light
does not activate.
NOTE: Unplug high frequency connection before attempting to work on this problem.
1. Check the Pilot Arc fuse (F2) located on the rear panel. An open fuse will indicate a short in the torch. If the fuse
is all right, then check the following:
a. With the machine power on, depress the torch switch. On the control board the LED 1 should be lit as long as
the switch is depressed. If not then check:
i. Turn power off to the machine. Unplug Control board. Put an ohmmeter across P5-1 and P5-2 to take
resistance reading. Depress torch switch. Meter should read a short. If not, then one of the following is
not working properly:
ii. Torch switch or the leads. Unplug the torch switch leads at the machine. Put a meter across the two plug
pins. Should read a short when the torch switch is depressed. If not, then either broken switch leads or
defective switch.
b. Check T2 transformer secondary voltages at the plugs P1 and P2. Refer to system schematic. Replace the
transformer if the correct secondary voltages are not present.
c. If everything above checks out all right, then the PCB1 Control Board should be replaced.
D. Fault light activates when torch switch is closed.
The Fault circuit is used to monitor conditions necessary for the safe operation of the PCM-875. The fault light
will glow amber under the following conditions and operations will come to a complete stop:
1. High/Low line voltage. The Fault Light will rapidly blink on and off (5 times per second). This indicates that
the input voltage is outside the “+” or “-” 15% safe operating range rating.
2. Flow fault - The fault light will be mostly on but will blink off for 1/10th of a second every second. This indicates
that the air flow is low.
a. Check the air pressure at the machine regulator. It should be adjusted to 65 psig. If no air pressure, check the
air at the supply point. Also, check for any obstructions in the air hose.
b. Air flow may be blocked at the torch tip. Check the torch consumables. Also check for any obstructions in the
torch leads.
NOTE: If above items check OK , the problem is internal. send unit to an Authorized Repair Station for repair.
c.. Put the ‘Air Check’ switch to On position. Air should flow through torch. If not, then the flow switch may be
stuck due to oil in the air. Clean air flow switch per supplier’s instructions or replace switch. To check if the
flow switch is open, put voltmeter leads between P1-12 and P1-1. It should read about 12 VDC. When the
flow switch closes, the voltage will drop to zero volts.
d. Air Check switch may also be defective if the air is flowing continuously or putting in the On position does
not turn air on.
3. Over Temperature. The fault light will be mostly off but will blink on for 1/10 of a second, every second. This
generally indicates that the duty cycle has been exceeded. Allow the power source to cool before returning to
operate.
a. Thermal switch may be open. It will open if the temperature at the IGBT base reaches 94oC. With the
machine power off, check the continuity between P1-1 and P1-2 of the control board. If the switch is OK, then
7
SECTION 3 TROUBLESHOOTING
the ohmmeter should read a direct short. If not then it should read open.
b. If the switch is defective, replace it. Clean the surface of the heat sink before installing the switch.
4. Over Current.
former has exceeded preset limits.
a. To check if the output is shorted, measure the resistance by putting the ohmmeter leads (make sure to
disconnect HI Frequency leads):”+” of the meter to Torch “+” output terminal and Work “-” lead of the meter
to the “-” output terminal. Reading should be about 2 K Ohms. Reverse the voltmeter leads, the resistance
reading should be less than 1.5 K Ohms.
b. If the resistance reading is different than above, check the torch, the output bridge and Filter Board (PCB-5).
The fault light will be on continuously. This indicates that the input current to the main trans-
E. Air is On but nothing happens when torch switch is operated.
1. Check the pilot arc fuse located on the rear panel. If it is open, nothing will happen when the torch switch is
depressed.
2. Check the torch. Make sure the heat shield is tight. PT27 torch has a built in safety circuit in which the torch will
not fire if heat shield is tightly secured.
3. Check to assure high frequency is present at the torch. If not, then listen for high frequency at the high frequency
generator. It is located on the bottom/right side of the unit. The high frequency gap is set between 0.71 to 0.78mm
Disconnect HI FREQUENCY leads. Check for 115 volt supply to the high frequency unit between P2-12 & P213 of the control board with torch switch closed.
4. With HI FREQUENCY leads disconnected, measure open circuit voltage. It should be 275 VDC between “Work”
and “Torch” terminals. If it is not present then any one of the following may not be working properly:
a. Check the operation of the Thermal Switch. See D.3.a. above.
b. Check Air Check switch operation. It might be stuck in On position. Pilot arc will not initiate if this switch is on
the ON position. (safety reasons)
c. Check air flow switch. There may be internal short. See D.2.c above.
d. Measure voltage across C1 or C2 capacitor. It should be as follows:
approx. 325 VDC for the 220 volt unit.
approx. 280 VDC to 325 VDC for the 400 volt unit
If not, one of following could be defective:
1). Check the capacitors C1 and C2 for any damage.
2.) Check input bridge/SCR Module (IBR) This can be checked without taking it out of the circuit using
an volt/ohmeter. Replace it if found defective. Follow bridge installation instructions.
3.) Check Inrush current resistor, R10 and SCR1. Both are located on the input bridge heat sink. Replace it if defective.
e. IGBTs (2 on 220 V, and 1 on the 400 V units) may be blown. See IGBT installation procedure. Before replac-
ing IGBTs, make sure to check the zener diodes and pico fuses on the IGBT driver boards.
8
SECTION 3 TROUBLESHOOTING
F. High Frequency and Pilot Arc are on but Main Arc does not transfer.
1. Make sure work clamp is connected to work material.
2. Check the torch. Replace consumables if necessary.
3. Make sure the current setting potentiometer is set above 10 amps. If it is, set below 10 amps, then HI FREQUENCY will go on and off at 5 sec intervals.
G. Poor Cutting Performance.
1. Check air supply regulator . It should be adjusted to 4.5-5.2 bar.
2. The air supplied to the torch should be free of oil and water.
3. Make sure the consumables in the torch are acceptable.
4. Check open circuit voltage. See E.4 above.
5. Check the output. Use a calibrated current probe capable of measuring 100 amps in the presence of high
frequency.
H. Air does not shut off.
1. Check air test, the gas solenoid valve is energized when the switch is in the “on” position.
2. Does air flow stop when the torch switch is unplugged? If yes, check and repair the torch. If not, send unit to an
Authorized Repair Station for repair.
a. Check voltage to solenoid coil, if present when torch switch is unplugged, replace PCB1. If voltage is “0”,
replace solenoid valve.
I. Main arc is difficult to start.
1. The most common reason is worn or missing consumables. Check and replace if necessary.
2. Input air must be clean and dry.
3. Input air pressure must be between 4.5 and 5.2 bar.
4. Torch connections must be tight.
5. Work cable and clamp must be in good condition and must make a good electrical connection to the material to
be cut.
6. If above items check OK , the problem is internal. send unit to an Authorized Repair Station for repair.
a. Missing or weak pilot arc. Check pilot arc fuse, open circuit voltage, pilot arc resistors and pilot arc wiring.
b. Inoperative starter board (PCB-5).
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