Multifunctional motor protection circuit

Working principle of the circuit: During normal operation, the voltage at both ends of the current sensing resistor is
divided by R2 and RP, and is used as the input signal of IC 4. IC4, R3~ Rg, C7~ Cl,, VDs~
VD, etc. constitute a half-wave rectified linear AC/DC conversion amplifier with average response.
During the positive half cycle, the signal flow is: IC4-CS-VD7-÷R6_+岛_+RP2-÷GND.
In the negative half cycle, the current leakage circuit is: GND-*RP2- R7- VD6_÷Cs- lC4.
The output passes through R8, cl, and Rg to obtain an average DC voltage that is linearly proportional to the input effective value.
This voltage passes through S. (S. is placed at the measuring end during normal operation) Enter the A/D converter
IC , and correctly adjust R)l and RP2, so that the LED can accurately display
the primary current of the current transformer BT. When used to protect a three-phase AC motor, this circuit can be used to detect
the current of any one of the three phases of the motor.