>
>>I am trying to come up with an intelligent process of selecting
>>components for the snubber circuit.
>>
>>I am getting very paranoid about possibly frying my welding machine
>>with this inverter circuit. I would like to avoid that at all costs.
>>
>>I have arrived to formulating my goal as: having a circuit such that
>>under no circumstances there would be voltages anywhere within the
>>welder that would exceed voltages that would normally exist _without_
>>my inverter.
>>
>>Otherwise, I am afraid, some existing components may be damaged as
>>they were possibly not designed for such higher voltages.
>>
>>Therefore, the first step would be to try to measure such max
>>voltages. The manual specifies max voltage as 150V. I think that it
>>would be good to try to limit voltages to 150V, that would be most
>>conservative.
>>
>>That brings up a question, how to select components.
>>
>>1. I would select the snubber caps such that the voltage generated
>>during commutation dead time would not exceed 150V (and should ideally
>>be about 100V). It seems that, assuming a 1 uS dead time and 360A
>>welding current (pessimistic assumptions for my 200a welder), 4 uF of
>>capacitance should take care of it. I hope that I can select resistors
>>such that there would be no dead time at all, but I think that I can
>>get to be no more than 1 uS dead time.
>>
>>2. I would also add a varistor set to start conducting at (having a
>>breakdown voltage of) 150V. Here I am somewhat confused. Varistors
>>have different ratings, DC, AC, etc. What varistor rating should I
>>choose so that it breaks down at 150V.
>>
>>If my post makes any sense at all, I would like to hear the answer to
>>my question in point 2. Thanks.
>
> I do fault your posts, because usually it's not clear exactly what
> configuration you are considering. That's because we must attempt
> to make "schematic" drawings from your incomplete or slightly vague
> verbal descriptions, which is not satisfactory. I suggest that you
> learn to make simple ASCII drawings and start illustrating your posts.
> You can also learn how to simplify your circuit and thereby show only
> the relevant parts in your post. Then we can give you accurate and
> useful analysis and advice. And we'll all be happy.
I made a little page explaining where the inverter will be placed, with links to PDF schematic of the welder and pictures of it.
formatting link
Your comment on my original question (how to properly select snubber characteristics) would be appreciated.
i