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newton brawn

Newbie level 6
Sep 9, 2009
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tig arc starter

Hi everyone !

Im newton, involved in the design of a arc starter for TIG arc weld. The project is running for 2 years, a lot of inprovements have been done.

Actually I need to synchronyze the arc starter with the line frequency (120Hz), a zero voltage cross circuit is required to drive a IGBT or a SCR

Suggestions or diagrams are welcome



tig welder arc starter schematic

Here more information:

The TIG welder is machine that supplies 30~250A, 20~30V to the welding electrode. The electrode to start to weld needs a high voltage pulse. This pulse is synchonized with the AC line (230V, 40A, single phase)

The arc starter shall provide a pulse (3600V, 0.22A, 18 microseconds) every time that the line voltage (220V, 60Hz) cross the AC line zero voltage.

This pulse charge a capacitor (0.001 microfarad) and them the cap dischage in a coil, producing high frequency high voltage. As the coil is coupled to electrode cable the pulse is transferred to the welding electrode, starting the welding.

The energy stored in the capacitor is about 007J or more. The current required to charge the cap is 0.22A during 18 microseconds.

The charge and discharge of the cap is 120 times per second. The input power is less than 1W.

As it can be seen, a flyback converter may produce the pulses. But, how to produce this pulse exactly when the voltage of the line is zero ??

I will be very happy for any sugestion.

Thanks in advance


you can use zero crossing detector (googling and search for the picture) ,2 x NE555, high voltage tesla coil (like the automotive vehicle coil), spark plug (for high voltage circuit safety), inductance coil for feeding to the arc welder ( the coil consist 2 winding cable : a few turn of negative cable of the arc welder and the next winding on the tesla coil (high voltage))

here is the result googling:

and the output from zero crossing detector can be triggerred out to 1st 555 timer circuit for approprriate constant RC time

the output of the 555 timer can be trigger the next 555 for astable multivibrator to produce 120 cycle for one second to switch the tesla coil to produce high voltage arc.

Hi Okto2005 !

Thank very much !

I whent to the site you has sujested and get full info for the ZCD. I already apply the info in a circuit with 1 transistor. The result is nice. Good synch so far.
The coil used is coiled by myself, working as flyback converter. The zcd "trigger " a mosfet, getting 5 kv @secondary.
If you want see the result , let me know your email
Thanks agn,

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