in this video {518} Inverter Welding Machine Repair Course / How To Repair #Inverter IGBT #Welding / welder #Machine / i demonstrated how to troubleshoot and repair the low voltage power supply in the inverter welding machine mma-200. its inrush protection bypass relay found faulty due to its coil winding open circuit. that was not shifting the relay armature contacts. so the machine was being operated on PTC all the time. i removed alll existing solder on high frequency smsps transformer, mosfet and the smps circuit. this solder was removed to remove dry solder joints and performed fresh soldering. then powered ON, the smps circuit started switching with only 3 volt dc instead of 24 volts. then i discovered that there a diode RCD snubber circuit was shorted between cathode and anode. i replaced that diode i got 24 volt on relay coil input terminals, and the welding machine started working.
in this way we can recover a dead welding machine
in video number 515 i shared part-2 of the welding machine repair course.
in part-1 of this course video number 514 ( • {514} Inverter Welding... ) i discussed Input Rectifier Circuit Explained & Troubleshooting. and this session i discussed full bridge / switching topology. it takes +330 vdc from dc rail, and drive from the pulse transformer which is driven the control card, this full bridge IGBTs will drive the power transfomer to produce output voltage, these output voltage will then rectified by full wave rectifier and will appear on output electrodes. control card will control and limit the duty cycle to limit the conduction of IGBTs to limit the current in the output terminal. the amount of flowing current in IGBTs and primary side of the transformer will translated into corresponding voltage by means of current transformer (CT). the output of the ct will then reach to control card, the control card will compare this CT voltage value and the required current value (in from of the tapped voltage by the current adjusting potentiometer on the front panel), and after comparing these both values the PWM controller UC3846 will adjust its duty cycle.
circuit diagram and how to repair mma-200 or mma200 mma250, mma160 and troubleshoot inverter IGBT based welding maching. this china MMA-200T Inverter IGBT Welder Machine - Circuit Explained & Troubleshooting Part -1, is single phase 220 VAC operated. it have a bridge rectifier which rectifies the main ac voltage into dc voltage, which are connected to pair of dc capacitors through a relay contacts and in parallel 110 ohms ntc resistor. this nts protects from inrush current and upon receiving relay drive signal it switches the rectified voltage to capacitors so, the ntc is bypassed to get full current to drive igbt.
after watching this video you will learn:-
how to #repair #inverter #igbt #welding machine or welder
2. functional description of inverter igbt welder machine
3. how to troubleshoot arc welding machine
4. how to understand mma-200 circuit diagram and how it works
5. if welding machine does not work, how you will repair
6. if main circuit breaker trips off when power switch is turned on
7. over current OC LED light turns on
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