W
W
eld
eld
in
in
g
g
in
in
v
v
er
er
t
t
er
er
10
10
0
0
A
A
Welding inverter is an alternative to conventional welding transformer. Modern semiconductors allows to replace the Welding inverter is an alternative to conventional welding transformer. Modern semiconductors allows to replace the traditional mains transformer with a switching supply, which is much lighter, smaller and allows easy current control via traditional mains transformer with a switching supply, which is much lighter, smaller and allows easy current control via potentiometer. The advantege is the fact that the output current is DC. Direct current is less dangerous than AC and prevents potentiometer. The advantege is the fact that the output current is DC. Direct current is less dangerous than AC and prevents arc extinction.
arc extinction.
For this inverter i chose topology, which is the most common in inverters - forward inverter with two switches. In my For this inverter i chose topology, which is the most common in inverters - forward inverter with two switches. In my article about
article about switchning suppliesswitchning suppliesit is a topology II.D. Input line voltage passes through the EMI filter and is smoothed withit is a topology II.D. Input line voltage passes through the EMI filter and is smoothed with large capacity. Since the switch-on pulse would be intolerable, there is a softstart circuit. After switching ON the primary large capacity. Since the switch-on pulse would be intolerable, there is a softstart circuit. After switching ON the primary filter capacitors charging through the resistors, which are subsequently eliminated by switchning ON the relay. As a filter capacitors charging through the resistors, which are subsequently eliminated by switchning ON the relay. As a switches the IGBT transistors are used. These are controlled through a forward excitation transformer TR2 and forming switches the IGBT transistors are used. These are controlled through a forward excitation transformer TR2 and forming circuits with BC327. Control circuit is UC3844. It's similar to UC3842, but equipped with pulse-width restriction to 50%. circuits with BC327. Control circuit is UC3844. It's similar to UC3842, but equipped with pulse-width restriction to 50%. Working frequency is 42kHz. Control circuit is powered by an auxiliary source of 17V. Current feedback, due to high Working frequency is 42kHz. Control circuit is powered by an auxiliary source of 17V. Current feedback, due to high currents, is using current transformer TR3. Voltage accros the resistor 4R7/2W is approximately proportional to the output currents, is using current transformer TR3. Voltage accros the resistor 4R7/2W is approximately proportional to the output current. Output current can be controlled by potentiometer P1, which determines the threshold of feedback. Threshold current. Output current can be controlled by potentiometer P1, which determines the threshold of feedback. Threshold voltage of the 3rd pin of UC3844 (sensor current) is 1V.
voltage of the 3rd pin of UC3844 (sensor current) is 1V.
Power devices require cooling. Most of the heat is dissipated in output diodes. Upper diode, consisting of 2x Power devices require cooling. Most of the heat is dissipated in output diodes. Upper diode, consisting of 2x DSEI60-06A, must in worst case handle the average current of 50A and the loss of 80W (both diodes). Lower diode
06A, must in worst case handle the average current of 50A and the loss of 80W (both diodes). Lower diode
STTH200L06TV1 (doube diode with both internal diodes in parallel) must in worst case handle the average current of 100A STTH200L06TV1 (doube diode with both internal diodes in parallel) must in worst case handle the average current of 100A and the loss of nearly 120W. Maximum total loss of the secondary rectifier is 140W. The heatsink must be able to handle it. and the loss of nearly 120W. Maximum total loss of the secondary rectifier is 140W. The heatsink must be able to handle it. To the thermal resistance you must include the junction-case Rth, case-sink Rth and sink-ambient Rth. Diodes don't have To the thermal resistance you must include the junction-case Rth, case-sink Rth and sink-ambient Rth. Diodes don't have insulation, the cathode is connected to the heatsink. Output choke L1 is therefore involved in the negative rail. It is
insulation, the cathode is connected to the heatsink. Output choke L1 is therefore involved in the negative rail. It is
advantageous because in this case there's no high-frequency voltage on the heatsink. You can use another type of diodes, for advantageous because in this case there's no high-frequency voltage on the heatsink. You can use another type of diodes, for example the parallel combination of a sufficient number of the most accessible diodes, such as MUR1560 or FES16JT. Note example the parallel combination of a sufficient number of the most accessible diodes, such as MUR1560 or FES16JT. Note that the maximum current of the lower diode is twice the current of the upper diode. Calculation of the loss of IGBTs is that the maximum current of the lower diode is twice the current of the upper diode. Calculation of the loss of IGBTs is more complicated because in addition to conductive losses there are switching losses. Loss of each transistor is up to about more complicated because in addition to conductive losses there are switching losses. Loss of each transistor is up to about 50W. It is necessary to cool the reset diodes UG5JT a rectifier diode bridge. Power loss of the reset diodes depends on the 50W. It is necessary to cool the reset diodes UG5JT a rectifier diode bridge. Power loss of the reset diodes depends on the construction TR1 (inductance, stray inductance), but is much smaller than the loss of IGBT. Rectifier bridge has a maximum construction TR1 (inductance, stray inductance), but is much smaller than the loss of IGBT. Rectifier bridge has a maximum loss of up to about 30W. UG5JT bridge and were placed on a common heatsink with IGBT. UG5JT diodes also can be
loss of up to about 30W. UG5JT bridge and were placed on a common heatsink with IGBT. UG5JT diodes also can be replaced with MUR1560 or FES16JT. During construction it is also necessary to decide the maximum loading factor of the replaced with MUR1560 or FES16JT. During construction it is also necessary to decide the maximum loading factor of the inverter, according to size of heatsinks, winding gauges and so on. It is also good to add a fan.
inverter, according to size of heatsinks, winding gauges and so on. It is also good to add a fan.
Switching transformer TR1 is wound on two ferrite EE cores, each with a central column section 16x20mm. The total Switching transformer TR1 is wound on two ferrite EE cores, each with a central column section 16x20mm. The total cross section is therefore 16x40mm, core must have no air gap. 20 turns primary winding is wound using 14 wires with a 0.5 cross section is therefore 16x40mm, core must have no air gap. 20 turns primary winding is wound using 14 wires with a 0.5 mm diamater. It would be better to use 20 wires, but they didnt fit to my core. Secondary winding has 6 turns of copper strip mm diamater. It would be better to use 20 wires, but they didnt fit to my core. Secondary winding has 6 turns of copper strip 36x0.5mm. Forward excitation transformer TR2 is made with an emphasis on low stray inductance. It is trifillary wound, 36x0.5mm. Forward excitation transformer TR2 is made with an emphasis on low stray inductance. It is trifillary wound, using three rolled up insulated conductors of 0.3 mm, and all the windings have 14 turns. Core is made of material H22, using three rolled up insulated conductors of 0.3 mm, and all the windings have 14 turns. Core is made of material H22, middle column has a diameter of 16mm, with no gaps. Current transformer TR3 is made from suppression chokes on the middle column has a diameter of 16mm, with no gaps. Current transformer TR3 is made from suppression chokes on the toroidal core. The original winding with 75 turns of 0.4 mm wire works as a secondary Primary has 1 turn. Orientation of all toroidal core. The original winding with 75 turns of 0.4 mm wire works as a secondary Primary has 1 turn. Orientation of all the transformer windings must be respected (see dots in schematic)! L1 is ferrite EE core, middle column 16x20mm. It has the transformer windings must be respected (see dots in schematic)! L1 is ferrite EE core, middle column 16x20mm. It has 11 turns of a copper strip 36x0.5mm and the total air gap in the magnetic circuit is 10mm. Its inductance is cca 12uH. 11 turns of a copper strip 36x0.5mm and the total air gap in the magnetic circuit is 10mm. Its inductance is cca 12uH.
Auxiliary switched supply, including TR4 is described in more detail
Auxiliary switched supply, including TR4 is described in more detail herehere. Simplest inverter on Pic 1 has no voltage. Simplest inverter on Pic 1 has no voltage feedback. Voltage feedback does not affect the welding, but affects the consumption and heat losses when idle. Without the feedback. Voltage feedback does not affect the welding, but affects the consumption and heat losses when idle. Without the output voltage feedback there is quite high output voltage (approximately 100V) and PWM controller running on max duty output voltage feedback there is quite high output voltage (approximately 100V) and PWM controller running on max duty cycle, thereby increasing consumption and heating components. Therefore, it is better to implement the voltage feedback. cycle, thereby increasing consumption and heating components. Therefore, it is better to implement the voltage feedback. You can inspire on Pic 2. The feedback can be connected directly because the driver is isolated from line. The reference You can inspire on Pic 2. The feedback can be connected directly because the driver is isolated from line. The reference voltage is 2.5V. Select the R2 to set the open circuit voltage. You can find useful info in
voltage is 2.5V. Select the R2 to set the open circuit voltage. You can find useful info in datasheet of UC3842, 3843, 3844,datasheet of UC3842, 3843, 3844,
3845
3845 or inor in another datasheetanother datasheet. Inspiration for modifications you can also find in. Inspiration for modifications you can also find in 3-60V 40A supply3-60V 40A supply.. Interesting links from which I drew:
Interesting links from which I drew:
http://svarbazar.cz/phprs/index.php?akce=souvis&tagid=3 http://svarbazar.cz/phprs/index.php?akce=souvis&tagid=3 http://leo.wsinf.edu.pl/~leszek/spawarki/ http://leo.wsinf.edu.pl/~leszek/spawarki/ http:// http:// www.y-u-r.narod.ru/Svark/svark.htmwww.y-u-r.narod.ru/Svark/svark.htm http://www.emil.matei.ro/weldinv3.php http://www.emil.matei.ro/weldinv3.php P
Plulugg& & PlPlayayIIGBT DrivGBT DriveersrsConcept Pin Options IGBT Drivers w/ Low Lead Times. Contact Us Today!Concept Pin Options IGBT Drivers w/ Low Lead Times. Contact Us Today! www.agileswitch.cowww.agileswitch.comm
Ba
BatterytteryWeldeWelder r MMacachinehineAC Pulse Spot Welder Machine & Capacitive Discharge Spot WelderAC Pulse Spot Welder Machine & Capacitive Discharge Spot Welder www.BatterySpace.com/WelderMachinewww.BatterySpace.com/WelderMachine
DataVox
DataVoxAPC Power & UPS for Houston Based -881-7407APC Power & UPS for Houston Based -881-7407 www.datavox.comwww.datavox.com
Page 1 of 16
Page 1 of 16
Welding inverter 100A
Welding inverter 100A
Create PDF with GO2PDF for free, if you wish to remove this line, click here to buy Virtual
http://nexor.electrik.org/svarka/barmaley/kosoy/shema.gif and a little modified: http://nexor.electrik.org/svarka/barmaley/kosoy1/shema.gif
Warning: I nverter circuits are electrically connected to the mains. I nverter containslarge capacitorsthat remain
charged even after turn off. Somecomponents(electrolytes, I GBT, ...) can explodeat fault. I nverter output voltage is
dangerous. I f defective or poor construction at the output can get the mainsvoltage or voltage higher than required.
I nverter can cause electric shock, burnsand fire. The arc createsa very intense light (with a large proportion of
ultraviolet), from which the personnel should be protected. I t can cause permanent eyedamage and skin burns
similar to solar. Weld evolve toxic gasesto beventilated.
Pic 1 - Homemade inverter welder (welding inverter) schematic (click to enlarge)
Pic 2 - Voltage feedback.
Tr1 Secondary made of a copper strip
Page 3 of 16
Welding inverter 100A
Secondary and a half of a core
Tr1 with wound primary
switching transformer Tr1 with core
Old Czechoslovak switching supply from the mainframe (5V 50A DBP 236 Kosire ZPA). From two such supplies I
Page 5 of 16
Welding inverter 100A
salvaged parts for the construction of the inverter (ferrites, coolers, distance posts, spools, inductors, copper strip ...)
Diodes STTH200L06TV1 and DSEI60-06A on the heatsink
heatsink with diodes, TR1, L1, copper tape
Gate drive transformer TR2 with trifillar winding (GDT)
Page 7 of 16
Welding inverter 100A
Tests of the exciter UC3844, TR2 and shaping circuit
Shaping circuit for gates
Ready to first start :).
Page 9 of 16
Welding inverter 100A
Short-term test for 150A - all survived:).
IGBT, bridge, reset diodes, forming circuits, GDT TR2 and the UC3844 driver.
Current transformer TR3
Page 11 of 16
Welding inverter 100A
It is welding :)
Measurement of arc voltage - long arc
Measurement of arc voltage - short arc
Page 13 of 16
Welding inverter 100A
The first test (the short-circuit current).
The second test, half the mains voltage, output voltage is too low to hold the arc. At the end you can se PWM on an oscilloscope.
Third test - it is allready welding.
Welding and safety at work - how it should never look like:).
Page 15 of 16
Welding inverter 100A
home
Super New Welding M achineSuper New Technology Plasma Welder All in One to Weld,Cut,Braze,Solder www.multiplaz.com Official Digi-Key SiteSearch Our Huge Selection of Quality Electronic Components Here! www.digikey.com
VoltageConverter 110/220Heavy Duty Voltage Transformers for 110V/220V volt Voltage Conversion www.220converters.com
