Ok so after simulating my project i understood how terrible I am at electronics:
I rethought it so forget about previous values.
I'll be using Current Transducer placed on output phase of inverter.
KlausST you are right IGBT current wont be exacly sinusoidal but at least its peak value will be coresponding to phase peak value.
On PCB i will only: measure and condition signal from transducer and then use window comparator to know when signal is above or below proper value.
Protection will be realised at FPGA - input of fpga will be pwm signals for transistors and this error signal from PCB (thats why i want 3.3V), output will be gate signals for transistors.
I will use closed loop Transducer. It output will be +-125mA (at 125A).
So what I think I need to do (but obviously i dont know exacly how):
Change current signal from transducer to voltage signal (via a resistor I guess?) (so my signal would be -Vt to +Vt)
Add an offset to signal so my signal will be 0-3.3V. (Can I just simply do:
- connect two sources via the same resistance? So do i even need op-amp?)
Then on this signal use window comparator. Here's general idea
LINK, but im confuse how should i connect it.
And from comparator get 3.3V (logic 1) or 0V (logic 0) to connect to FPGA. In link logic 1 will be when my signal is between the values (better option would be logic 1 for outside - should I only swap + and - of comparators ?)
Thank you very much for previous posts showing me im a noob :<
But last thing I have to ask, could you show me a simplified scheme how should it be done ?