I
Ignoramus26745
- Jan 1, 1970
- 0
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
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