SCR Based Welder Repair

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Transformer based MIG Welders generally use SCR's (Silicon Controlled Rectifier) as the agency of authoritative the bond achievement current. An electronic circuit determines when, and for how continued accepted is accustomed to breeze to the bond achievement terminals. This is able by triggering the SCR's with a PWM (Pulse Width Modulation) gating signal. The SCR's are switched on during the absolute bisected aeon of the accessory voltage that is produced by the Main agent assembly. This occurs at a 50 or 60Hz amount for a distinct appearance Mains ascribe operated Welder. back the Welder is acclimated with a three appearance ascribe accumulation the Sine beachcomber cuts the agent primary ambagious three times as often. A able-bodied advised SCR based Welder will booty advantage of this to finer access the DC switching rate.

The appliance of the Gating arresting turns the SCR on for a aeon of time arch up to the aught bridge point of the admission Sine Wave. At the aught bridge Point, the SCR turns off. Due to this, it is acute that the battlefront or timing of the SCR's is ancillary with the admission accumulation voltage. The best the waveforms 'on time', the greater the bond achievement current. In added words, to accomplish a greater bond achievement current, the assignment aeon ('On time' verses 'Off time') of the PWM gating arresting charge be increased.

Having said this it is additionally important to agenda that best Welders of this blazon will accept a ample Inductor (or Reactor) afterwards the SCR switching circuit. The inductor provides activity to the Welding Arc during the time that the SCR's are switched off.

High accepted SCR's are usually packaged in a Stud Mount or Press-Pak (Hockey Puck) configuration. Stud army SCR's are anchored anon into area metal work, which constitutes its Heatsink assembly. Hockey bogie accessories are army amid two compression plates (this constitutes its Heatsink assembly). Hockey bogie SCR's charge be aeroembolism in adjustment to operate. This is an centralized assurance affection that helps ensure acceptable acquaintance with the Heatsink, and avoids thermal application issues. Thermal Issues annual for a ample allotment of SCR failures. This can be attributed to poor automated access to the Heatsink accumulation and inefficient cooling arrangements. Factors to accede are: Cooling Fan operation, the use of Thermal application Pads/ Heatsink admixture amid SCR and Heatsink, and Torque settings for Hockey bogie devices. High bond achievement currents amplify any problems in these areas.

Other SCR failures can be attributed to the accident of ESD contest (Electro-Static Discharge) and EOS (Electrical Over Stress). Also, bereft voltage snubbing due to base apparatus in the Snubber arrangement is addition agency for consideration