ESAB Precision Plasmarc EPP-600 User manual

EPP-600
Plasma Power Source
Instruction Manual
0558004600

This equipment will perform in conformity with the description thereof contained in this manual and accompa-
nying labels and/or inserts when installed, operated, maintained and repaired in accordance with the instruc-
tions provided. This equipment must be checked periodically. Malfunctioning or poorly maintained equipment
should not be used. Parts that are broken, missing, worn, distorted or contaminated should be replaced imme-
diately. Should such repair or replacement become necessary, the manufacturer recommends that a telephone
or written request for service advice be made to the Authorized Distributor from whom it was purchased.
This equipment or any of its parts should not be altered without the prior written approval of the manufacturer.
The user of this equipment shall have the sole responsibility for any malfunction which results from improper
use, faulty maintenance, damage, improper repair or alteration by anyone other than the manufacturer or a ser-
vice facility designated by the manufacturer.
BE SURE THIS INFORMATION REACHES THE OPERATOR.
YOU CAN GET EXTRA COPIES THROUGH YOUR SUPPLIER.
These INSTRUCTIONS are for experienced operators. If you are not fully familiar with the
principles of operation and safe practices for arc welding and cutting equipment, we urge
you to read our booklet, “Precautions and Safe Practices for Arc Welding, Cutting, and
Gouging,” 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 be-
fore installing or operating this equipment.
CAUTION
USER RESPONSIBILITY

TABLE OF CONTENTS
1.0 SafetyPrecautions.................................................................................. 93
2.0 Description......................................................................................... 95
2.1 Introduction.................................................................................... 95
2.2 General Specifications .......................................................................... 95
2.3 DimensionsandWeight ........................................................................ 96
3.0 Installation.......................................................................................... 97
3.1 General......................................................................................... 97
3.2 Unpacking ..................................................................................... 97
3.3 Placement...................................................................................... 97
3.4 InputPowerConnection........................................................................ 98
3.4.1 PrimaryPower............................................................................ 98
3.4.2 InputConductors ........................................................................ 99
3.4.3 InputConnectionProcedure.............................................................. 99
3.5 OutputConnection............................................................................100
3.5.1 OutputCables(customersupplied) ......................................................100
3.5.2 OutputConnectionProcedure........................................................... 101
3.6 ParallelInstallation ............................................................................ 101
3.7 CNCInterfaceCables...........................................................................104
4.0 Operation .........................................................................................105
4.1 BlockDiagramCircuitDescription.............................................................. 105
4.2 ControlPanel..................................................................................108
4.2.1 Modes of Operation: Cutting and Marking Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .111
4.3 SequenceofOperation.........................................................................112
4.4 ArcInitiationSettings...........................................................................113
4.4.1 Enable/DisableArcInitiationTimer.......................................................114
4.4.2 AdjustArcInitiationTimer................................................................114
4.4.3 ArcInitiationControls ....................................................................115
4.4.4 StartCurrentandUp-SlopeTimer.........................................................115
4.5 EPP-600V-ICurves..............................................................................116
5.0 Maintenance.......................................................................................285
5.1 General........................................................................................285
5.2 Cleaning......................................................................................285
5.3 Lubrication....................................................................................286
Section / Title Page

92
TABLE OF CONTENTS
6.0 Troubleshooting...................................................................................287
6.1 General........................................................................................287
6.2 FaultIndicators................................................................................287
6.3 Fault Isolation .................................................................................290
6.3.1 Fans Not Working .......................................................................290
6.3.2 PowerNotOnorLowVoltage............................................................290
6.3.3 FaultLightIllumination..................................................................291
6.3.4 TorchWillNotFire.......................................................................295
6.3.5 Fuses F1 and F2 Blown...................................................................296
6.3.6 Intermittent, Interrupted or Partial Operation ............................................296
6.4 TestingandReplacingComponents............................................................298
6.4.1 PowerRectifiers.........................................................................299
6.4.2 Troubleshooting Freewheeling Diode and IGBTs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
6.4.3 PowerShuntInstallation.................................................................303
6.4.4 Procedure for Verifying Calibration of Digital Meters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
6.5 Control Circuit Interface Using J1 and J6 Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305
6.6 Auxiliary Main Contactor (K3) and Solid State Contactor Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
6.7 Main Contactor (K1A, K1B and K1C) Activation Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
6.8 ArcCurrentDetectorCircuits...................................................................309
6.9 Current Control Pot and Remote Vref . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
6.10 PilotArcHI/LOandCut/MarkCircuits .........................................................311
6.11 Current Transducer for Optional Output Current Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .312
7.0 ReplacementParts..................................................................................313
7.1 General.........................................................................................313
7.2 Ordering .......................................................................................313
Section / Title Page

SECTION 1 SAFETY PRECAUTIONS
1.0 Safety Precautions
Users of ESAB welding and plasma cutting equipment have the ultimate responsibility for ensuring that anyone
who works on or near the equipment observes all the relevant safety precautions. Safety precautions must meet
the requirements that apply to this type of welding or plasma cutting equipment. The following recommendations
should be observed in addition to the standard regulations that apply to the workplace.
All work must be carried out by trained personnel well acquainted with the operation of the welding or plasma
cutting equipment. Incorrect operation of the equipment may lead to hazardous situations which can result in
injury to the operator and damage to the equipment.
1. Anyone who uses welding or plasma cutting equipment must be familiar with:
- its operation
- location of emergency stops
- its function
- relevant safety precautions
- welding and / or plasma cutting
2. The operator must ensure that:
- no unauthorized person stationed within the working area of the equipment when it is started up.
- no one is unprotected when the arc is struck.
3. The workplace must:
- be suitable for the purpose
- be free from drafts
4. Personal safety equipment:
- Always wear recommended personal safety equipment, such as safety glasses, flame proof
clothing, safety gloves.
- Do not wear loose fitting items, such as scarves, bracelets, rings, etc., which could become
trapped or cause burns.
5. General precautions:
- Make sure the return cable is connected securely.
- Work on high voltage equipment may only be carried out by a qualified electrician.
- Appropriate fire extinquishing equipment must be clearly marked and close at hand.
- Lubrication and maintenance must not be carried out on the equipment during operation.

SECTION 1 SAFETY PRECAUTIONS
WELDING AND PLASMA CUTTING CAN BE INJURIOUS TO YOURSELF AND
OTHERS. TAKE PRECAUTIONS WHEN WELDING OR CUTTING. ASK FOR
YOUR EMPLOYER’S SAFETY PRACTICES WHICH SHOULD BE BASED ON
MANUFACTURERS’ HAZARD DATA.
ELECTRIC SHOCK - Can kill.
- Install and earth (ground) the welding or plasma cutting unit in accordance with applicable standards.
- Do not touch live electrical parts or electrodes with bare skin, wet gloves or wet clothing.
- Insulate yourself from earth and the workpiece.
- Ensure your working stance is safe.
FUMES AND GASES - Can be dangerous to health.
- Keep your head out of the fumes.
- Use ventilation, extraction at the arc, or both, to take fumes and gases away from your breathing zone
and the general area.
ARC RAYS - Can injure eyes and burn skin.
- Protect your eyes and body. Use the correct welding / plasma cutting screen and filter lens and wear
protective clothing.
- Protect bystanders with suitable screens or curtains.
FIRE HAZARD
- Sparks (spatter) can cause fire. Make sure therefore that there are no inflammable materials nearby.
NOISE - Excessive noise can damage hearing.
- Protect your ears. Use earmuffs or other hearing protection.
- 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!
WARNING

95
SECTION 2 DESCRIPTION
2.1 Introduction
The EPP power source is designed for high speed plasma mechanized cutting applications. It can be used with
other ESAB products such as the PT-15 and PT-600 torches along with the Smart Flow II, a computerized gas
regulation and switching system.
50 to 600 amperes cutting current range
Forced air cooled
Solid state DC power
Input voltage protection
Local or remote front panel control
Thermal switch protection for main transformer and power semiconductor components
Top lifting rings or base forklift clearance for transport
Parallel secondary power source capabilities to extend current output range.
•
•
•
•
•
•
•
•
EPP-600 400V,
50 / 60Hz CE
EPP-600 460V,
60Hz
EPP-600 575V,
60Hz
Part Number 0558005701 0558005702 0558005703
Output
(100 % duty cycle)
Voltage 200 VDC
Current range DC (marking) 12A to 600A
Current range DC (cutting) 50A to 600A
Power 120 KW
* Open Circuit Voltage (OCV) 410 VDC 427 VDC 427 VDC
Input
Voltage (3-phase) 400 V 460 V 575 V
Current (3- phase) 206A RMS 179A RMS 143A RMS
Frequency 50/60 HZ 60 Hz 60 Hz
KVA 142.7 KVA 142.6 KVA 142.9 KVA
Power 129.9 KW 129.8 KW 129.6 KW
Power Factor 91.0 % 91.0% 91.0%
Input Fuse Rec. 250A 250A 200A
2.2 General Specifications
* Open circuit voltage is reduced to 290V in the marking mode.

96
SECTION 2 DESCRIPTION
Weight = 925.34 kg. (2040 lbs.)
2.3 Dimensions and Weight
114.3 mm
45.00” 94.6 mm
37.25”
102.2 mm
40.25”

97
SECTION 3 INSTALLATION
3.1 General
FAILURE TO FOLLOW INSTRUCTIONS COULD LEAD TO DEATH, IN
JURY OR DAMAGED PROPERTY. FOLLOW THESE INSTRUCTIONS TO
PREVENT INJURY OR PROPERTY DAMAGE. YOU MUST COMPLY WITH
LOCAL, STATE AND NATIONAL ELECTRICAL AND SAFETY CODES.
WARNING
3.2 Unpacking
Using one lifting eye will damage sheet metal and frame.
Use both lifting eyes when transporting with overhead method.
Unit weighs over 907 kg. (2000 lbs.) Use approved straps or cables in
good condition.
CAUTION
Inspect for transit damage immediately upon receipt.
Remove all components from shipping container and check for loose parts in container.
Inspect louvers for air obstructions.
•
•
•
3.3 Placement
Note:
Use both lifting eyes when transporting from overhead.
A minimum of 0.61 M (2 ft.) clearance on front and back for cooling air flow.
Plan for top panel and side panels having to be removed for maintenance, cleaning and inspection.
Locate the EPP-600 relatively close to a properly fused electrical power supply.
Keep area beneath power source clear for cooling air flow.
Environment should be relatively free of dust, fumes and excessive heat. These factors will affect cool-
ing efficiency.
•
•
•
•
•
Conductive dust and dirt inside power source may cause arc flash-
over.
Equipment damage may occur. Electrical shorting may occur if dust is
allowed to build-up inside power source. See maintenance section.
CAUTION
CAUTION

98
SECTION 3 INSTALLATION
3.4 Input Power Connection
ELECTRIC SHOCK CAN KILL!
PROVIDE MAXIMUM PROTECTION AGAINST ELECTRICAL SHOCK.
BEFORE ANY CONNECTIONS ARE MADE INSIDE THE MACHINE, OPEN
THE LINE WALL DISCONNECT SWITCH TO TURN POWER OFF.
WARNING
3.4.1 Primary Power
EPP-600 is a 3-phase unit. Input power must be provided from a line (wall) disconnect switch that contains fuses
or circuit breakers in accordance to local or state regulations.
Recommended input conductor and line fuse sizes:
* Sizes per National Electrical Code for a 90° C (194˚ F) rated copper conductors @ 40° C (104˚ F) ambient. Not more
than three conductors in raceway or cable. Local codes should be followed if they specify sizes other than those listed
above.
** During heavy duty cutting at 600A, input current can momentarily rise above 200A and cause nuisance blowing of
200A fuses. When cutting currents are below 500A, 200A fuses are sufficient.
To estimate the input current for a wide range of output conditions, use the formula below.
Dedicated power line may be necessary.
EPP-600 is equipped with line voltage compensation but to avoid
impaired performance due to an overloaded circuit, a dedicated
power line may be required.
NOTICE
Input at Rated Load Input and Ground
conductor* CU/
mm2(AWG)
Time delay
Fuse size
(amperes)
Volts Amperes
400 206 95 (4/0) 250
460 179 95 (3/0) 250**
575 143 50 (1/0) 200
Rated load is output of 600A at 200V
Input current = (V arc) x (I arc) x 0.688
(V line)

99
Customer supplied
May consist either of heavy rubber covered copper conductors (three power and one ground) or run
in solid or flexible conduit.
Sized according to the chart.
•
•
•
3.4.2 Input Conductors
Input conductors must be terminated with ring terminals.
Input conductors must be terminated with ring terminals sized for
12.7 mm (0.50”) hardware before being attached to the EPP-600.
NOTICE
1. Remove left side panel of the EPP-600
2. Thread cables through the access opening in the rear panel.
3. Secure cables with a strain relief or conduit coupling (not sup-
plied) at the access opening.
4. Connect the ground lead to the stud on the chassis base.
5. Connect the power lead ring terminals to the primary termi-
nals with supplied bolts, washers and nuts.
6. Connect the input conductors to the line (wall) disconnect.
3.4.3 Input Connection Procedure
1
3
2
1 = Primary Terminals
2 = Chassis Ground
3 = Power Input Cable Access Opening (Rear Panel)
SECTION 3 INSTALLATION

100
ELECTRIC SHOCK CAN KILL!
RING TERMINALS MUST HAVE CLEARANCE BETWEEN SIDE PANEL
AND MAIN TRANSFORMER. CLEARANCE MUST BE SUFFICIENT TO
PREVENT POSSIBLE ARCING. MAKE SURE CABLES DO NOT INTER
FERE WITH COOLING FAN ROTATION.
IMPROPER GROUNDING CAN RESULT IN DEATH OR INJURY.
CHASSIS MUST BE CONNECTED TO AN APPROVED ELECTRICAL
GROUND. BE SURE GROUND LEAD IS NOT CONNECTED TO ANY PRI
MARY TERMINAL.
ELECTRIC SHOCK CAN KILL! DANGEROUS VOLTAGE AND CURRENT!
ANY TIME WORKING AROUND A PLASMA POWER SOURCE WITH COV
ERS REMOVED:
DISCONNECT POWER SOURCE AT THE LINE (WALL) DISCONNECT.
HAVE A QUALIFIED PERSON CHECK THE OUTPUT BUS BARS (POSI-
TIVE AND NEGATIVE) WITH A VOLTMETER.
•
•
3.5 Output Connections
WARNING
WARNING
WARNING
3.5.1 Output Cables (customer supplied)
Choose plasma cutting output cables (customer supplied) on the basis of one 4/0 AWG, 600 volt insulated cop-
per cable for each 400 amps of output current.
Note:
Do not use 100 volt insulated welding cable.
SECTION 3 INSTALLATION

101
SECTION 3 INSTALLATION
3.5.2 Output Connection Procedure

Access Panel
1. Remove access panel on the lower front of the power source.
2. Thread output cables through the openings at the bottom of the front panel or at the bottom of the power source im-
mediately behind the front panel.
3. Connect cables to designated terminals mounted inside the power source using UL listed pressure wire connectors.
4. Replace panel removed during the first step.
Two 600 power sources may be connected together to extend the output current range.
3.6 Parallel Installation
CAUTION
Parallel power source start currents exceed recommended amounts
when cutting below 100A.
Use only one power source for currents below 100A.
We recommend disconnecting the negative lead from the second-
ary power source when changing to currents below 100A. This lead
should be safely terminated to protect against electric shock.

102
SECTION 3 INSTALLATION
Note:
Primary power source has the electrode (-) conductor jumpered. The secondary power source has the
work (+) jumpered.
1. Connect the negative (-) output cables to the arc starter box (high frequency generator).
2. Connect the positive (+) output cables to the workpiece.
3. Connect the positive (+) and negative (-) conductors between the power sources.
4. Connect the pilot arc cable to the pilot arc terminal in the primary power source. The pilot arc connection in the second-
ary power source is not used. The pilot arc circuit is not run in parallel.
5. Set the Pilot Arc HIGH / LOW switch on the secondary power source to“LOW”.
6. Set the Pilot Arc HIGH / LOW switch on the primary power source to“HIGH”.
7. If a remote 0.00 to +10.00VDC current reference signal is used to set the output current, feed the same signal into both
power sources. Connect J1-A (common) of both power sources together and connect J1-B (0.00 - 10.00 VDC) of both
power sources together. With both power sources operating, the output current can be predicted using the following
formula: [output current (amps)] = [reference voltage] x [100]
Connections for parallel installation of two EPP-600 power sources
Secondary Power
Source Primary Power
Source
work
(+)
electrode
(-) pilot arc
3 - 4/0 600V
positive leads
to workpiece
1 - 14 AWG 600V
lead to pilot arc con-
nection in arc starter
box (h.f. generator)
3 - 4/0 600V
negative leads
in arc starter box
(h.f. generator)
EPP-600 EPP-600
work
(+)
electrode
(-)
4/0 600V
cable jumpers
between units

103
SECTION 3 INSTALLATION
ELECTRIC SHOCK CAN KILL!
EXPOSED ELECTRICAL CONDUCTORS CAN BE HAZARDOUS!
DONOTLEAVEELECTRICALLY“HOT“CONDUCTORSEXPOSED. WHEN
DISCONNECTING THE SECONDARY POWER SOURCE FROM THE PRI
MARY, VERIFY THE CORRECT CABLES WERE DISCONNECTED. INSU
LATE THE DISCONNECTED ENDS.
WHEN USING ONLY ONE POWER SOURCE IN A PARALLEL CONFIGU
RATION, THE NEGATIVE ELECTRODE CONDUCTOR MUST BE DISCON
NECTEDFROMTHESECONDARYPOWERSOURCEANDTHEPLUMBING
BOX. FAILURE TO DO THIS WILL LEAVE THE SECONDARY ELECTRI
CALLY “HOT”.
WARNING
Secondary Power
Source
Primary Power
Source
work
work electrode
electrode
3 - 4/0 600V
positive leads
to workpiece
3 - 4/0 600V
negative leads
in arc starter box
(h.f. generator)
Disconnect negative
connection from sec-
ondary power source
and insulate to con-
vert from two to one
power source
EPP-600 EPP-600
DO NOT OPERATE THE EPP600 WITH COVERS REMOVED.
HIGH VOLTAGE COMPONENTS ARE EXPOSED INCREASING SHOCK
HAZARD.
INTERNAL COMPONENT MAY BE DAMAGED BECAUSE COOLING
FANS WILL LOSE EFFICIENCY.
WARNING
The EPP-600 does not have an ON/OFF switch. The main power is controlled through the line (wall) disconnect switch.

104
SECTION 3 INSTALLATION
3.7 CNC Interface Cables
A- 0558005528 Interface Cable Connection
Connection from 10 pin Plug J6 to CNC interface connector.
B- 0558005530 Interface Cable Connection
Connection from 19 pin Plug J1 to CNC interface connector.
Note:
Interface cables are NOT supplied with the EPP-
600 Power Supply and are provided as reference
information only.
B
A

105
SECTION 4 OPERATION
4.1 Block Diagram Circuit Description
Left PWM / Gate Drive Board
Galvanic Isolator PWM Gate
Drive
Galvanic Isolator
PWM Gate
Drive
(Master)
(Slave)
Right PWM / Gate Drive Board
2
H
Sync Signal For Alternate Switching
3 Phase
Input
T1 Main
Transformer
-310V DC Bus
Bus Rectifiers
300U120’s
Cap.
Bank
Control Circuit
Feedback For Fast Inner Servos
Error Amplifiers
Galvanic Isolator
0.0 - 10.0V DC Vref
Iout = (Vref) x (80)
CNC Common
(Floating) S
T“T” Common Connected to Earth Grounded Work Through the “+” Output
Feedback for Constant
Current Servo
Twisted Pair
Left
IGBT Modules
Right IGBT Modules
T
Left Hall
Sensor
Right Hall Sensor
L1
Blocking Diodes
Blocking Diodes
L2
Free Wheeling Diodes
T
T1 T1
Contact on Pilot
Arc Contactor
425V Peak 250V Peak
Boost Starting
Circuit
Biased Snubber
R (boost)
R (snub)
Pilot Arc
Circuit
Precision
Shunt
ELECTRODE
NOZZLE
WORK
EPP-600
BLOCK DIAGRAM

106
SECTION 4 OPERATION
4.1 Block Diagram Circuit Description (con’t.)
The power circuit utilized in the EPP-600 is commonly referred to as a Buck Converter or a Chopper. High speed electronic
switches turn on and off several thousand times per second providing pulses of power to the output. A filter circuit, con-
sisting primarily of an inductor (sometimes called a choke), converts the pulses to a relatively constant DC (Direct Current)
output.
Although the filter inductor removes most of the fluctuations from the “chopped” output of the electronic switches, some
small fluctuations of output, called ripple, remain. The EPP-600 utilizes a patented power circuit combining the output
of two choppers, each providing approximately half the total output, in a manner that reduces ripple. The choppers are
synchronized so that when the ripple from the first chopper is increasing output, the second chopper is decreasing output.
The result is the ripple from each chopper partially cancels the ripple from the other. The result is ultra low ripple with a
very smooth and stable output. Low ripple is highly desirable because torch consumable life is often improved with low
ripple.
The graph below shows the effect of ESAB’s patented ripple reduction using two choppers synchronized and switching
alternately. Compared to two choppers switching in unison, the alternate switching typically reduces ripple a factor of 4
to 10.
EPP-600 Output RMS Ripple Current Versus Output Voltage
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
0 50 100 150 200 250 300
RMS Ripple Current (Amperes)
Output Voltage (Volts)
Choppers Synchronized and Switching in Unison (10KHz Ripple)
Patented EPP-600
Choppers Synchronized and Switching
Alternately (20KHz Ripple)

107
The Control Circuit contains regulating servos for both choppers. It also contains a third servo that monitors the total
output current signal fed back from the Precision Shunt. This third servo adjusts the two chopper servos to maintain an
accurately controlled output current commanded by the Vref signal.
The Vref circuitry is galvanically isolated from the rest of the power source. The isolation prevents problems that can arise
from “ground” loops.
Each chopper, the Left Master, and the Right Slave, contain their own PWM / Gate Drive PC Boards mounted directly on the
IGBT’s. This circuitry provides the on / off PWM (Pulse Width Modulation) signals to drive the IGBT’s. The Left (Master) PWM
provides a synchronized clock signal to its own Gate Drive circuitry as well as to the Right (Slave) Gate Drive circuitry. It is
through this synchronized signal that the IGBT’s from the two sides switch alternately reducing output ripple.
The EPP-600 contains a Boost Supply for providing approximately 425V DC for arc starting. After the cutting arc is estab-
lished, the Boost Supply is turned off with a contact on the Pilot Arc Contactor (K4).
A Biased Snubber reduces the voltage transients created during cutting arc termination. It also reduces the transient volt-
ages from a parallel power source thus preventing damage to the power source.
The Pilot Arc Circuit consists of the necessary components for establishing a pilot arc. This circuit disengages when the
cutting arc is established.
SECTION 4 OPERATION
The EPP-600 Block Diagram (after Subsection 6.4.4) shows the main functional elements of the power source. T1, the Main
Transformer, provides isolation from the primary power line as well as the proper voltage for the 310V DC Bus. The Bus Rec-
tifiers convert the three phase output of T1 to the 310V bus voltage. A capacitor bank provides filtering and energy storage
that supplies power to the high speed electronic switches. The switches are IGBT’s (Insulated Gate Bipolar Transistors). The
310V bus provides power for both the Left (Master) Chopper and the Right (Slave) Chopper.
Each chopper contains IGBT’s, Free Wheeling Diodes, a Hall Sensor, a Filter Inductor, and Blocking Diodes. The IGBT’s are
the electronic switches that, in the EPP-600, turn on and off 10,000 times per second. They provide the pulses of power
filtered by the inductor. The Free Wheeling Diodes provide the path for current to flow when the IGBT’s are off. The Hall
Sensor is a current transducer that monitors the output current and provides the feedback signal for the control circuit.
The Blocking Diodes provide two functions. First, they prevent the 425V DC from the Boost Starting Circuit from feeding
back to the IGBT’s and the 310V Bus. Second, they provide isolation of the two choppers from one another. This permits
independent operation of each chopper without the other chopper functioning.
4.1 Block Diagram Circuit Description (con’t.)

108
SECTION 4 OPERATION
4.2 Control Panel
A - Main Power
Indicator illuminates when input power is applied to the power source.
B - Contactor On
Indicator illuminates when the main contactor is energized.
C - Over Temp
Indicator illuminates when power source has overheated.
D - Fault
Indicator illuminates when there are abnormalities in the cutting process or
when the input line voltage falls outside of the required nominal value by
±10%.
E - Power Reset Fault
Indicator illuminates when a serious fault is detected. Input power must be
disconnected for at least 5 seconds and then reapplied.
F - Current Dial (Potentiometer)
EPP-600 dial shown. EPP-600 has a range of 12 to 600 A. Used only in panel
mode.
C
B
D
E
K
JIHF
G
A
L