Welder Plasma
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How does a plasma cutter power supply work?
i have built a small stick welder, and now i plan to convert it to a plasma cutter but i need to know what the requirements are to create the plasma stream, i know it needs to be DC current. i just need to know about the power supply i plan to buy the torch head for one but if you have any info on how i could built a torch head at home please let me know.
PS: I am 15 but i know what i am doing
Are you looking to buy one or build one ? To get a controllable cut, the power supply needs to provide clean output characteristics and the ability control it. Some info :
Power Supplies
PAC power supplies are direct current electrode negative (DCEN). The process requires a constant source of DC and a high open circuit voltage (OCV) to initiate the arc (typically at least twice the operating voltage). The following is a summary of some basic differences among PAC power supply types.
DC Droopers. Early plasma systems included drooper power supplies, named for their drooping output power curves. These units provided a high OCV and relatively stable current and operating voltage. They used a fixed-output DC rectifier bridge consisting of a series of diodes to convert AC power from a transformer into usable DC for the cutting process.
These simple systems created a lot of power but wasted energy and had too much ripple in their output power. (Ripple is fluctuations in DC output that cause a rough cut and short part life.) To further regulate power output, multiple transformers could be used, each providing a higher level of output current.
Reactors. Reactor power supplies were the next step in power regulation. These used a reactor device to control the amount of AC voltage supplied to the bridge rectifier. The reactor consisted of a group of AC coils with a DC winding around it. The current in the DC winding controlled the amount of AC that passed through the reactor, which created an adjustable transformer that allowed variable DC output from the bridge.
SCRs. Silicon-controlled rectifiers (SCRs) are another type of continuously variable output power supply. SCRs convert three-phase AC power from a transformer directly to DC. They require huge capacitor banks and large transformers. SCRs are large and powerful and are used for high-amp PAC systems but are not well-suited to hand-held applications.
Switch-mode. Switch-mode power supplies use transistors to modulate DC power after the rectifier. Choppers are a type of switch-mode power supply that use power semiconductor devices such as isolated gate bipolar transistors (IGBTs), which take raw DC with ripple and chop it up, rapidly switching the power on and off to smooth the output characteristics. IGBTs can be fired much faster than old reactor-type power supplies. The result is a very smooth output power curve.
Inverters are another type of switch-mode power supply. They use devices such as transistors on the input side of the power train to raise the frequency of the AC into the transformer. Higher frequency input allows a much smaller transformer to be used. Because a smaller transformer is used, inverters are much lighter and more portable than conventional power supplies, making them ideal for hand-held applications.
Early inverter power supplies were limited by low output current and complicated design and poor reliability. When problems occurred, sophisticated techniques and troubleshooting were required to solve them.
Today's inverters are more reliable, robust, and powerful. Most manual PAC systems now use inverter or switch-mode technology. These sophisticated, electronically or microprocessor-controlled devices are better able to tolerate variations in line voltage, take more abuse in the field, and deliver better cutting performance while consuming less power
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