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Kemppi Oy
SERVICE MANUAL
Minarc Evo 150/180
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Kemppi Oy
CONTENTS
1. READ THIS FIRST ........................................................................................................................................... 1
2. GENERAL......................................................................................................................................................... 2
3. TECHNICAL INFORMATION ........................................................................................................................... 3
3.1. Technical data ........................................................................................................................................... 3
3.2. Wiring diagram .......................................................................................................................................... 5
3.3. Construction .............................................................................................................................................. 6
3.3.1. Inner structure .................................................................................................................................... 7
3.3.2. Z001 main circuit card structure ........................................................................................................ 8
3.3.3. A001 control card structure ................................................................................................................ 9
3.4. Description of operation .......................................................................................................................... 10
3.4.1. Z001 Main circuit card ..................................................................................................................... 10
3.4.2. A001 Control card ............................................................................................................................ 11
4. SERVICE INSTRUCTIONS ............................................................................................................................ 12
4.1. Programming ........................................................................................................................................... 12
4.2. Calibration ............................................................................................................................................... 12
4.2.1. Functions and buttons ..................................................................................................................... 12
4.2.2. Calibration parameters .................................................................................................................... 15
4.2.3. Calibration procedure ...................................................................................................................... 15
4.3. Measurements and tests ......................................................................................................................... 16
4.3.1. Z001 Main circuit card ..................................................................................................................... 16
4.3.1.1. Input rectifier and PFC circuit ................................................................................................... 17
4.3.1.2. IGBT ......................................................................................................................................... 19
4.3.1.3. Secondary rectifier.................................................................................................................... 21
4.3.1.4. Voltages .................................................................................................................................... 22
4.3.1.5. Overheat protection .................................................................................................................. 23
4.3.2. A001 control card ............................................................................................................................. 24
4.3.3. Cooling fan ....................................................................................................................................... 26
4.3.4. Low voltage tests ............................................................................................................................. 26
4.3.5. Safety tests ...................................................................................................................................... 26
4.4. Semiconductor installation ...................................................................................................................... 26
4.4.1. Rectifier/PFC module and IGBT ...................................................................................................... 26
4.4.2. Secondary rectifier ........................................................................................................................... 27
4.5. Final testing ............................................................................................................................................. 27
4.5.1. Load bank test ................................................................................................................................. 28
4.5.2. Test welding ..................................................................................................................................... 28
5. NOTES ........................................................................................................................................................... 29
APPENDIX .......................................................................................................................................................... 29
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Service manual Minarc Evo 150 and 180
Version 1.3
30.9.2015
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Kemppi Oy
1. READ THIS FIRST
230VAC 50/60Hz and 390VDC or higher are inside the machine
Before removing any covers or commencing any testing or measurement disconnect the power source
from the mains voltage
Dangerous DC voltage may still exist after the removal of the input voltage. Machine discharges the
voltage while it is turned off, but it is always better to ensure this by measuring the voltage
Wait at least one minute for the capacitors to become discharged.
Digital multimeters (later DMM) may give different values depending the specifications they have. For
example diode measuring values may vary between the DMM models. In this manual Fluke 179 DMM is
used.
This machine has all the control circuits in the primary side and special attention must be considered
while working with the internal parts.
The device may be repaired only by a person legally authorized to perform electric work.
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Service manual Minarc Evo 150 and 180
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2. GENERAL
Minarc Evo 150 and 180 are new generation small MMA machines. It is not based on any existing
machine. It is totally new design electrically and mechanically. Machine has a power factor correction in
the primary side to meet the latest European regulations.
The Minarc Evo machines are for MMA-welding and scratch TIG can be used as well. MMA open circuit
voltage is 90VDC or 30VDC with VRD activated.
Minarc Evo can be connected to the mains supply of 230VAC 1~. PFC makes possible to weld with the
full power (MMA 140A/MMA 170) even when modern circuit breakers are used.
Minarc Evo control card software cannot be reprogrammed in the field.
Overvoltage watch is 300VAC and under voltage watch is 110VAC; voltage must be increased back to
160VAC to get the inverter back to full operation after the under voltage situation.
Current range is 10-140A in MMA and 10-150A in TIG mode for Evo 150 and 10-170A in MMA and 10-
180A in TIG for Evo 180.
Minarc Evo discharges the DC link voltage after switching the main switch off by running the cooling fan
as long as the control electronics is wake.
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Service manual Minarc Evo 150 and 180
Version 1.3
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3. TECHNICAL INFORMATION
3.1. Technical data
Minarc Evo 150
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Service manual Minarc Evo 150 and 180
Version 1.3
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Minarc Evo 180
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Service manual Minarc Evo 150 and 180
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3.2. Wiring diagram
Latest version with better quality is available at Kemppi Channel.
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3.3. Construction
The cooling fan is installed so that the air flows from the left side plate to Z001 card. Air comes out
through the front and the back plate grills.
Left side
Front
Right side
Back
Left side, side plate
removed
Left side plate with
cooling fan
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3.3.1. Inner structure
1. Main switch
2. Primary heat sink
3. T001 main transformer
4. Secondary heat sink
5. Secondary choke
6. Remote control socket
7. A001 control card
8. Z001 main circuit card
1.
2.
3.
4.
5.
7.
6.
8.
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3.3.2. Z001 main circuit card structure
1.
2.
3.
4.
5.
6.
7.
9.
8.
1. Primary rectifier and PFC module
2. IGBT module
3. DC-link capacitors
4. Main transformer
5. Secondary diodes, zero side + stress reduction resistor
6. Negative output connector
7. Positive output connection
8. Secondary diodes, positive side
9. X9 connector to A001 card
10. PFC choke
10.
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Service manual Minarc Evo 150 and 180
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3.3.3. A001 control card structure
1. X2 service connector (not field programmable, serial bus
connection is in the primary side)
2. MMA/TIG selection
3. Remote ON/OFF
4. Microcontroller
5. Analogic potentiometer
6. 7-segment display
7. X1 connector to main circuit card (flat cable)
8. Overheat LED
9. VRD LED
10. Welding machine ON LED
11. TIG mode LED
12. MMA mode LED
13. Remote ON LED
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
13.
12.
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Service manual Minarc Evo 150 and 180
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3.4. Description of operation
Minarc Evo 150/180 can be divided to two parts: Z001 main circuit card and A001 control/panel card
Z001 main circuit card
o Input rectifier and PFC circuit
o IGBT module
o Main transformer
o Secondary rectifier
o Secondary choke
o Auxiliary switching power supplies
o Current measuring
A001 control card
o Inverter control
o Panel display
o Current set value adjustment
o Panel buttons functions
o Panel LEDs
o Remote control functions
3.4.1. Z001 Main circuit card
Main circuit card; coil components and their functions:
Main transformer turn ratio is 4:1; its primary winding is 20 turns (wire) and secondary
5 (foil). Transformer has 140/170°C PTC for over heat protection. While temperature
rises the resistance stays under the 100Ω until the breakdown point (140°C), then the
PTC goes to high-resistance mode (>10kΩ). Control logic stops inverter when the
resistance value rises over the 1,5kΩ.
Secondary choke L3 inductance is 5μH and its winding has13 turns. Choke slows the
secondary voltage changes and works as energy storage in the long short circuits.
PFC choke works together with PFC circuit. It has 66 turns.
Main circuit card itself provides the following functions:
DC-link soft start charging and over voltage protection circuit. It avoids full power
connection if the primary has a short circuit or main supply voltage rises over the
safety limit.
EMC filtering circuit filters EMC disturbances from main supply voltage to machine
and vice versa.
The single-phase rectifier/PFC module rectifies the mains voltage (nominal 230VAC)
to PFC circuit, approx. nominal value of 320VDC. Rectifier holds four power diodes.
PFC circuit is integrated in the same module with rectifier diodes. PFC circuit (two
parallel IGBTs, two diodes in series and PFC choke) keeps the primary voltage and
current in the same phase. This rises the power factor up to 0,99. PFC is boost type
and raises the DC-link voltage up to 390VDC.
Power section is based on dual forward architecture with 63 kHz switching frequency.
It has two stages: ON and OFF/demagnetizing. OFF-stage must last longer time than
ON-stage because main transformer needs to be demagnetized. Otherwise it goes to
saturation.
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Both modules have integrated NTC resistors for over heat protection: In 0-40° C
environment temperature range, resistance varies between the 60-15kΩ if the
machine is cool. In the overheat situation NTC resistance lowers down to 2kΩ and
even lower. Machine stops the inverter in the 2kΩ point. Note that NTC has
descending nominal curve: When temperature rises resistance lowers.
Z001 card has an auxiliary power supply which delivers auxiliary voltages to Z001
and A001 cards. Primary side: +16VDC for the upper IGBT gate buffer, floating
+16VDC and floating GND for the lower IGBT gate buffer, and +24VDC for the
cooling fan and charging relay. Secondary side: +12VDC (tolerance ±1V) for the
remote controller and reference GND.
o Note! Voltages are in the primary side (except +12VDC) so be careful while
measuring the voltages.
DC-link with two 470μF electrolytic capacitors. Machine current is measured in the
DC-link and feedback goes to the A001 card. DC-link is discharged by cooling fan
while main switch is turned off.
Secondary rectifier has two working and three demagnetizing diode cases. Each
case holds two diodes so total quantity is doubled.
OCV (open circuit voltage) adjustment circuit keeps the voltage stable and at a safe
level.
Secondary shunt resistor is only for measuring the secondary current for the
displays. Machine uses primary current measuring for inverter feedback.
Remote control connection circuit with galvanic isolation. Remote controller reading
is in the A001 card.
Cooling fan control circuit. Control signal comes from the A001 card.
Dual forward inverter gate driver circuit. Control signal comes from the A001 card.
Secondary voltage monitoring in VRD mode. Limit is 32VDC and if voltage is higher
VDR led is off in A001 card.
3.4.2. A001 Control card
Minarc Evo 150 and 180 are using same control card but software is different so also
spare part codes are different. Cards are not programmable in field.
Microcontroller controls e.g. current and voltage measuring and adjustment,
protection circuits, remote control function, panel button function, panel LEDs,
provides serial bus and saves calibration data.
o Note that calibration and service connection is in the primary side without
galvanic isolation. This is meant only for production use
Control card has control buttons for remote control ON/OFF and TIG/MMA selection.
It has analogue potentiometer for welding current set value. These buttons and
potentiometer are used for the machine calibration also.
Card LEDs have following functions: Machine ON, TIG/MMA selected, overheat
protection ON and VRD activated. VRD LED lights only when it is activated, so in TIG
mode and during the welding in MMA mode it is off.
7-segment display shows the current set value while not welding. During the welding
it shows actual welding current value. In calibration mode is shows the measured
current value of machine.
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A001 card has auxiliary voltages +16VCD (X1-1) and +24VDC (X1-2) from the Z001
main circuit card PSU. A001 card makes +5VDC.
o Note! Voltages are in the primary side so be careful while measuring
them.
4. SERVICE INSTRUCTIONS
4.1. Programming
Minarc Evo 150/180 has a microprocessor on the A001 card. This can only be reprogrammed in Kemppi
production because great care must be taken, because the connection is in the primary potential and
without galvanic isolation.
Normally there is no need for reprogramming, but in a special case, the only possibility is to fit a
replacement control card that is factory programmed. In these cases please contact:
technicalservice@kemppi.com
4.2. Calibration
Minarc Evo must always be calibrated if an A001 control card or a Z001 main circuit card is replaced with
a new one. Otherwise machine maximum/minimum current and/or panel display may be out of range.
There are only two buttons and three LEDs to be used in calibration procedure. See the following
example and guide on how to use the different functions in calibration mode.
4.2.1. Functions and buttons
To enter the calibration mode press and hold TIG/MMA and Remote buttons and switch on the machine.
Keep pressing the buttons until calibration mode activated: On LED is pulsing at the rate 0,1s ON and
0,9s OFF.
Picture1. Entering the calibration mode.
1. Press and hold
both buttons
Entering the calibration mode:
2. Switch on
the machine
3. ON LED
starts blinking
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Moving from parameter to parameter can be done by combining the Remote ON/OFF and TIG/MMA
buttons in the following sequence.
Picture2. Moving between parameters.
Parameter 2: Current multiplier
(150A)
Parameter 3: Display current
offset min. (10A)
2. Press to go to the next
parameter
1. Press and hold
Moving to next parameter:
Parameter 2: Current multiplier
(150A)
Parameter 3: Display current offset
min. (10A)
2. Press to go to the next
parameter
1. Press and hold
Moving to previous parameter:
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Parameter values can be changed by using the buttons Remote ON/OFF and TIG/MMA separately.
Picrute3. Changing parameter value.
Increasing or decreasing the parameter value, affects the machine in different ways depending on the
parameter. Example above is for illustration only, see the chapter “Calibration procedure” to get the step
by step instructions on how to proceed.
Parameter 3: Display
current offset min. (10A)
Increasing the parameter value:
Parameter 3: Display
current offset min. (10A)
Press to increase the parameter value
Press to decrease the parameter value
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4.2.2. Calibration parameters
Picture4. All calibration parameters.
4.2.3. Calibration procedure
If the parameter values go out of range or some other problems occur, use the parameter 0 to reset the
calibration data. Then it is easier to start from the beginning of calibration.
Switch off the machine and disconnect the welding cables
Enter the calibration mode (procedure on picture1)
Move to parameter 0 above (procedure on picture2)
Change its value (procedure on picture3). ON LED starts to cycle 0,9s ON and 0,1s
OFF.
Once machine is switched off, restart the machine to get the parameter values reset.
Note! This parameter is only for resetting the calibration data; this is not the factory settings recall as in
the other Kemppi machines. After resetting the values, procedure must be carried out to ensure the
machine working properly.
To get satisfactory and reliable calibration result welding current must be measured. A current clamp
meter is easiest and accurate enough for this purpose. If a clamp meter is not available, a standard shunt
resistor and multimeter can be used. In this case two welding cables are needed and the shunt should be
connected between them. Kemppi shunts have been stamped with the current-voltage relation, so it is
easy to use a standard multimeter with low voltage function (mV) for measuring the current value.
0. Reset the
calibration data
(all LEDs off)
1. Current offset
min. (10A)
2. Current
multiplier (150A)
4. Display
current multiplier
(150A)
5. Remote
controller offset
min (10A)
6. Remote
controller MMA
multiplier (140A)
7. Remote
controller TIG
multiplier
(150A)
(all LEDs on)
3. Display
current offset
min. (10A)
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Service manual Minarc Evo 150 and 180
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The following example uses a clamp meter. See the previous two chapters to study button configurations
(Pictures 2 and 3) and parameter info (Picture4).
1. Switch off the machine. If a resistive load is available, this is the best option, connect the
resistive load via welding cables between the machine output Dix connectors. The machine must be switched off to avoid arcing while connecting the cable. If a resistive load
is not available, it is possible to use a long welding cable (4 to 10 meters if possible) the
longer the cable the more accurate the current measuring.
2. Enter the calibration mode, ON LED starts plinking (procedure on picture1).
3. Move to the calibration parameter 1 (procedure on Picture2). Turn the potentiometer to
minimum and check the measured current in the clamp meter value. Adjust parameter
value (procedure on Picture3) as close to 10A as possible, below 10A is better than
above it.
4. Move to parameter 2 (procedure on Picture2). Turn the potentiometer to maximum and
check the measured current in the clamp meter value. Adjust parameter value (procedure
on Picture3) as close to 150A as possible, above 150A is better than below it.
5. Move to parameter 3 (procedure on Picture2). Turn the potentiometer to minimum and
check the panel display value. Adjust parameter value (procedure on Picture3) as close
to 10A as possible, exact value is ideal. If this is not possible, select the one below 10A.
6. Move to parameter 4 (procedure on Picture2). Turn the potentiometer to maximum and
check the panel display value. Adjust parameter value (procedure on Picture3) as close
to 150A as possible, exact value is ideal. If this is not possible, select the one above
150A.
7. Switch off the machine, disconnect the welding cable or load and connect the remote
controller.
8. Enter the calibration mode (procedure on Picture1) and move to parameter 5 (procedure
on Picture2). Turn the remote controller potentiometer to minimum and check the panel
display value. Adjust parameter value (procedure on Picture3) so that it is three steps
below the point where it changes from 11A to 10A.
9. Move to parameter 6 (procedure on Picture2). Turn the remote controller potentiometer to
maximum and check panel display value. Adjust parameter value (procedure on Picture3)
so that it is three steps above the point where it changes from 139A to 140A.
10. Move to parameter 7 (Picture2). Turn the remote controller potentiometer to maximum
and check the current set value in the panel display. Adjust parameter value (procedure
on Picture3) so that it is three steps above the point where it changes from 149A to 150A.
11. The calibration is now completed and once machine is switched off and restarted, the
parameters are saved.
At this point it is good to check that the current set value can be adjusted from 10A to 140/150A with both
panel potentiometer and remote controller.
4.3. Measurements and tests
4.3.1. Z001 Main circuit card
Power stage is divided in to two parts: rectifier/PFC module and IGBT module. They can be tested
separately by using simply digital multimeter.
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4.3.1.1. Input rectifier and PFC circuit
Mains supply voltage must not be connected during the rectifier/PFC module diode measuring.
In many cases of primary side failures input rectifier or the PFC circuit diodes may be broken. Rectifier
diodes can be measured one by one, but PFC circuit diodes only in two groups, because they are
internally connected parallel and in series. Two diodes between the PFC IGBT collector and emitter are in
parallel with IGBTs and the other two diodes are in series from PFC input to the DC-link positive.
Check the diodes using a multimeter diode function to measure their threshold voltage. Diodes must be
measured both forward bias and reverse bias condition to make sure they are satisfactory. See the
following pictures and table to make all the necessary measurements.
L1
L2
IGBT diodes
Series
diodes
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Diode
Positive test lead
Negative test lead
Result
Diode 1 forward bias
L1
Rectifier output
0,2-0,7VDC
Diode 3 reverse bias
L1
GND
No value
Diode 1 reverse bias
Rectifier output
L1
No value
Diode 3 forward bias
GND
L1
0,2-0,7VDC
Diode 2 forward bias
L2
Rectifier output
0,2-0,7VDC
Diode 4 reverse bias
L2
GND
No value
Diode 2 reverse bias
Rectifier output
L2
No value
Diode 4 forward bias
GND
L2
0,2-0,7VDC
GND
Rectifier output
L1
L2
L2
L1
1 3 2
4
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Diode group
Positive test lead
Negative test lead
Result
Series diodes forward bias
PFC input
DC-link positive
0,2-0,5VDC
IGBT diodes reverse bias
PFC input
GND
No value
Series diodes reverse bias
DC-link positive
PFC input
No value
IGBT diodes forward bias
GND
PFC input
0,3-0,7VDC
4.3.1.2. IGBT
Mains supply voltage must not be connected during the IGBT module diode measuring.
IGBT module can be tested by a multimeter when using the diode tester function. The module holds four
diodes and if IGBT is damaged, in many cases these will be defective. They can be measured only in
pairs if main transformer primary is connected, if it is removed all the four diodes can be measured
separately.
GND
PFC input
DC-link
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Check the diode groups using the multimeter diode function to measure their threshold voltage. Diodes
must be measured both forward bias and reverse bias condition to make sure they are satisfactory. See
following pictures and table to make all the necessary measurements.
Mianrc Evo 150 card:
IGBT 1 emitter and IGBT 2 collector are connected
via main transformer; it is not possible to measure all
the four diodes separately without disconnecting the
transformer primary.
Main
transformer
primary
winding
GND
IGBT 1
emitter
DC-link
IGBT 2 collector
1
2
IGBT 1 emitter
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Minarc Evo 180 card:
IGBT
Positive test lead
Negative test lead
Result
IGBT 1 diode + upper separate
diode; forward bias condition
IGBT1 emitter/IGBT 2
collector
DC-link positive
0,2-0,7VDC
IGBT 2 diode + lower separate
diode; reverse bias condition
IGBT1 emitter/IGBT 2
collector
GND
No value
IGBT 1 diode + upper separate
diode; reverse bias condition
DC-link positive
IGBT1 emitter/IGBT
2 collector
No value
IGBT 2 diode + lower separate
diode; forward bias condition
GND
IGBT1 emitter/IGBT
2 collector
0,2-0,7VDC
If the transformer primary is disconnected, IGBT 1 emitter and IGBT 2 collector connection points can be
used separately to measure diodes one by one. In this case the table must checked twice: first using the
IGBT 1 emitter point only and then the IGBT 2 collector point.
4.3.1.3. Secondary rectifier
Mains supply voltage must not be connected during the secondary rectifier diode measuring.
Use a digital multimeter to test the secondary diodes. Diodes are in groups, so it is not possible to
measure them one by one unless they removed from the board and measured separately.
Diode
Positive test lead
Negative test lead
Result
Forward bias
Negative output terminal
Positive output terminal
0,2-0,6VDC
Reverse bias
Positive output terminal
Negative output terminal
No value
GND
IGBT 1
emitter
DC-link
IGBT 2
collector
1
2
IGBT 1 emitter
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4.3.1.4. Voltages
The Z001 main circuit card has the DC-link voltage after the input rectifier and several auxiliary voltages
made by the auxiliary PSU. Floating point voltage and remote control reference voltage need their own
ground points to get right values.
Note! Most voltages are in the primary side. Even touching the ground level may affect electric
shock because there is up to 120VDC between the ground and protective earth.
+16VDC,
C26 left side
connection point
+24VDC,
V46 bottom leg
Primary GND,
V62 leg on the upper
side, second from left
Floating +16VDC,
C56 upper connection
point
Floating GND,
C56 bottom connection point
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4.3.1.5. Overheat protection
Main transformer PTC is soldered to the Z001 main circuit card:
Measure the resistance: It should be less than 100Ω
In over temperature situation PTC goes to high-resistance mode (>10kΩ)
Machine gives temperature alarm at 1,5kΩ
A broken PTC has usually hundreds of kilo ohms resistance or no value at all.
+12VDC,
Test point on the right
side of R22
Reference ground, N3
right side, third leg
from top
+390VDC,
DC-link,
TP4
Primary GND,
TP5
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Both primary modules NTCs are integrated inside the module:
Measure the resistance, it should be between 60-15kΩ in a cool machine (in
environment temperature 0-40°C)
While temperature rises resistance lowers and at 2kΩ point the inverter stops and gives
overheat alert.
A broken NTC has usually hundreds of kilo ohms resistance, no value at all or short
circuit.
4.3.2. A001 control card
PTC common point
Main transformer PTC
resistor
NTC common point
Rectifier/PFC module NTC
resistor
NTC common point
IGBT module NTC resistor
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Control card voltages have common ground, on the primary side. +16VDC and +24VDC PSU are located
on the Z001 card. +5VDC is made on the A001 card.
Note! Voltages are in the primary side. Even touching the ground level may affect electric shock
because there is up to 120VDC between the primary ground and protective earth.
GND,
S5 upper leg
+5VDC
Test point between the S5
switch legs. Also N3
second leg from the lower
left
+16VDC,
Test point
GND,
C26 left side or upper leg
of S5 as shown in the
previous picture
+24VDC,
R17 left side connection point
GND,
C1 right side
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4.3.3. Cooling fan
Cooling fan gets the power from the +24VDC line. Voltage can be measured in the X7 connector (X7-1
+24VDC and X7-2 GND). Note that the cooling fan has delayed starting.
The cooling fan is installed so that the air flows from the left side plate to Z001 card. Air comes out
through the front and the back plate grills.
4.3.4. Low voltage tests
Low voltage test cannot be done to Minarc Evo 150 machine.
4.3.5. Safety tests
Safety tests are made normally, but PE conductivity test cannot be tested, because there are no outer
parts connected to PE. Do not use PE continuity test equipment with high testing current.
PE wire conductivity should be measured only by DMM with resistance function to continuity. Measure
the resistance between the main supply cable terminal and Z001 X3.
4.4. Semiconductor installation
It is a must be to use torque screwdriver while tightening any power components onto the heat
sink. See following sections for tightening torques.
4.4.1. Rectifier/PFC module and IGBT
MinarcEvo 150/180 has soldered input rectifier/PFC and IGBT modules and it is not possible to change
them separately. Only reliable way to replace the module(s) is to change the whole Z001 main circuit
card.
The heat sink paste should be spread on to the modules in an even layer by using fingers. Then the card
should be immediately mounted onto the heat sink, this minimizes the possibility of any contamination
(dirt etc.) getting between the components.
The hexagonal fixing screws for the IGBT module are tightened (stage 1) to 1 Nm. And after few minutes
the module screws can be finally tightened (stage 2) to a torque of 2,0 Nm.
Once all four hexagonal screws are tightened to right torque, the module support cap screws can be
fastened. The idea is to support the module to the PCB with the plastic caps, instead of the component
soldered legs. The torx screws for caps can be tightened only up to 0,5 Nm, or otherwise PCB may bend.
Hexagonal screw
Support cap
Support cap screw
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4.4.2. Secondary rectifier
The heat sink transfer compound should spread in an even layer onto the heat sink. Then the card should
be immediately mounted onto the heat sink, this minimizes the possibility of any contamination (dirt etc.)
getting between the components.
The torx fixing screws in diodes are tightened to 1,2 Nm and the resistor (a smaller case than the diodes)
to 0,7 Nm.
4.5. Final testing
After the machine repair and low voltage tests, it is good practice to carry out some load tests and finish
with some test welds. Only then is it possible to guarantee the machine is working correctly.
Hexagonal screws
Support cap
Support cap screw
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Service manual Minarc Evo 150 and 180
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4.5.1. Load bank test
CC (MMA and TIG machines) curve’s secondary voltage can be calculated when a certain current is set:
MMA mode:
2004,022 IU
TIG mode:
1004,022 IU
Voltage has to be set for the nominal curve to get the correct output power. E.g. when making a PTC test
the correct values must be used to meet the duty cycle specified in technical specification.
Most useful tests to be made with a load bank are to check maximum and minimum current and panel
display values.
The following example uses 140A so the correct voltage can be calculated using the equation below:
VA
IU
AI
6,252004,0140
2004,0
140
22
2
Output voltage should be 25,6V.
Example: Minarc Evo 150 MMA mode load bank test, welding current 140A and output voltage 25,6V
Turn the machines main switch OFF
Connect machine to the load bank and check that there is no load added.
Turn the machines main switch ON,
Adjust machine current to desired level (this example uses 140A)
Add some load to get the inverter operate, be fast in switching because arcing may exist
between the connection surfaces of the switch
Measure load voltage by a DMM
Add or decrease load to get the desired voltage
If using active load bank, instead of increasing or decreasing load, it is only necessary to select MMA
nominal curve and then set the test current value on the machine. The Load follows automatically the
current value and the output voltage will be correct.
4.5.2. Test welding
Test welding is important for having final and reliable information, if the maintenance / repair has been
made successfully.
In some cases a load bank test alone does not give the absolute truth if the machine is functioning
properly or not. Test welding will show if the power source and control panel are working together in a
natural state.
While carrying out test welding, it is useful to test at different current settings to see if the current is right
and ignition good.
Pay attention especially to the features that were the original reason for the maintenance work.
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Service manual Minarc Evo 150 and 180
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5. NOTES
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