How Are Such Circuits Designed Actually?

Start by taking some high power electrical circuit design courses.

Knowledge cannot be assimilated by discourse unless you have 9 months.

Self study may help and below is a web site that may be useful.

Others are available by searching.

an introduction to high frequency pipe and tube welders

The first thing you need to learn is how to read the Russian language. Then you decipher the the components and how they interact with each other, then you wire them together, apply power. And if done properly you will have harnessed the magic smoke!

I didn't notice that the schematics were in Russian until you mentioned it, I was busy tracing out the circuit groups and leaving the ICs as 'black box devices' until I needed to work out what the ICs were for.

It would make your life easier if they were translated into your native language. At least you'd know the names and maybe even some values.

Values are easy, they're still using Arabic numerals, and I remember that in Europe they use . for , and , for .

Resisters are in ohms, capaciters are most likely in microfarads, inductors are typically in milihenris, and all the semiconductors have their ID numbers listed.

You must take into consideration all relevant factors....What materials you are going to weld, what the throughput is going to be, what are the available power sources likely to be...What budget do you have to work with....what special considerations has the customer requested, if any....Then you might look at other designs to see if they would be suitable for this application.....if they have any design flaws or customer complaints of problems with premature failure under certain conditions...Then you can adapt an existing design or modify it, or completely start from scratch if nothing seems suitable.....The design must be easy to assemble and maintain, and use 'off the shelf' parts, if possible....Then you design and build an engineers model to test the design...knowing what current will be required and range of control, design life, and other factors, will define what basic components will be needed...

http://en.wikipedia.org/wiki/Welding_power_supply

People ask me "How do you do that?". I tell them, I don't know. I see pictures and I write them down. My brain does all the creative work. It's beyond my conscious mind. I assess the need and wait for ideas to pop out. I realize this will in no way help you. Sorry about that.

If you are referring to designing electronic circuits from scratch, then it will be very hard for a beginner since it involves /requires a lot of thorough understanding and knowledge of inter-related different fields. It is kind of complicated...

Now-a-days I can pretty much say from experience that almost all the different types of electronic circuitries utilizing different ypes of components have already been designed and tested. Designed, tested and used in thousands of different and varying applications as intended for by the original designers and different device manufacturers..

However, although they are readily available, there are a lot of other things you need to do to them to make them work and function as you choose to?

One of the basic things needed, as an example is, you will need to understand how each of those pre-designed circuits operate, how to interface / couple individual circuitries to function and behave as you desired.

And it is imperative, very important to understand impedance matching for maximum power transfer as an another pre-requisite of circuit design!

I think the above simplified overview of what the minimum tasks are involved in a "design" work should help you decide what you really think you can as oppose to what you really want, and base on what you really are at present?

Good luck!