Phase Current Sensing Circuit: Q&A

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SUMMARY

The discussion focuses on the design and analysis of a phase current sensing circuit utilizing a shunt resistor and operational amplifier (opamp). Key components include resistors R45, R37, and capacitor C26, which form a filter circuit with a time constant of approximately 100 ns, primarily aimed at removing RF interference. The gain of the shunt amplifier is established at 15, with a configuration of a 2kΩ input resistance and a 30kΩ output resistance. It is confirmed that capacitor C26 does not introduce significant phase delay compared to the time constant of R55 and C32, which is 1 µs.

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TL;DR
Phase current sensing and the phase delay
This is the phase current sensing circuit
1689757794065.png


Here the phase currents are converted to voltages by passing through shunt resistor and fed to the opamp. Two questions i have
a. Can I analyze the R45, R37, C26 as one filter circuit and the remaining as other circuit for gain?
b. The phase currents are converted into voltages after passing through shunt resistor and are available at the output of the opamp. Does the capacitor C26 add any phase delay?
 
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R45, R37, C26 has a product of about 100 ns, so it will only remove RF.

PhysicsTest said:
Does the capacitor C26 add any phase delay?
Not really. The TC is small compared to R55 * C32 = 1 us, which is probably an antialiasing filter before an A to D converter.

The gain of the shunt amplifier is set by series 1k + 1k = 2k input, to 30k output, gain = x15.
 
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