[EE] inverter welder, high frequency start, typical circuit?

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[EE] inverter welder, high frequency start, typical circuit?

Jason White-20
Hi everyone,

I recently stumbled across a few circuits for (Stick/TIG) welders and
plasma cutters.

I have read that high frequency start involves generating 15kV on the
output of the welding machine. Does anyone know how or have any resource
showing how the high voltage "coexists" on the outputs stage of an inverter
based welder without causing damage?

On many machines the square wave output of the inverter passes through a
large inductor or step down transformer. I suppose HF losses in said device
would go a long way towards protecting the inverter's switching
transistors.


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Jason White
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Re: [EE] inverter welder, high frequency start, typical circuit?

madscientistatlarge
Links to some or all of these would be greatly appreciated.


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‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Sunday, June 28, 2020 3:19 PM, Jason White <[hidden email]> wrote:

> Hi everyone,
>
> I recently stumbled across a few circuits for (Stick/TIG) welders and
> plasma cutters.
>
> I have read that high frequency start involves generating 15kV on the
> output of the welding machine. Does anyone know how or have any resource
> showing how the high voltage "coexists" on the outputs stage of an inverter
> based welder without causing damage?
>
> On many machines the square wave output of the inverter passes through a
> large inductor or step down transformer. I suppose HF losses in said device
> would go a long way towards protecting the inverter's switching
> transistors.
>
>
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Jason White
>
> ------------
>
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist



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Re: [EE] inverter welder, high frequency start, typical circuit?

Bob Blick-5
In reply to this post by Jason White-20
In its simplest form, imagine a 2nd-order 2-way crossover network in a loudspeaker cabinet. Same idea in reverse. You can make it as simple or as sophisticated as you need. And different companies decide how involved they want to get. Basically it is a frequency combining network.

As far as protection, it's harder to protect against the voltage of load dump that happens when you stick the electrode to the workpiece and then pull it off. Caps, MOVs, and even spark gaps are sometimes employed. Good current limiting is also very important. If your welder is set to 100A and 22V, you don't want current to increase dramatically into a short circuit.

Download the manual for a good welder, say a Miller syncrowave 200 or 250 and look at the schematic diagram. They don't include board schematics, but all the big stuff is there.

Friend;y regards, Bob

________________________________________
From: [hidden email] <[hidden email]> on behalf of Jason White
Sent: Sunday, June 28, 2020 2:19 PM
To: Microcontroller discussion list - Public.
Subject: [EE] inverter welder, high frequency start, typical circuit?

Hi everyone,

I recently stumbled across a few circuits for (Stick/TIG) welders and
plasma cutters.

I have read that high frequency start involves generating 15kV on the
output of the welding machine. Does anyone know how or have any resource
showing how the high voltage "coexists" on the outputs stage of an inverter
based welder without causing damage?

On many machines the square wave output of the inverter passes through a
large inductor or step down transformer. I suppose HF losses in said device
would go a long way towards protecting the inverter's switching
transistors.


--
Jason White


--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist