CRD-30DD12N-K reference design : the three-phase current measurement strategy

gkim

Hello,

With respect to the reference design of CRD-30DD12N-K, I have a few questions on the three-phase current measurement strategy.

Let me describe it with the phase C current as an example.

The current measurement circuit for phase C on the main board is uploaded as below.

The phase C current is measured by the 1:200 current transformer and it is full-wave rectified by the diode bridge circuit.

The current measurement circuit for phase C on the control board is uploaded as below.

The current signal is converted into the voltage signal by this circuit.

Now I have a few questions on these phase current measurement circuits as follows:

(1) When the current signal is full-wave rectified as aforementioned, how can the DSP know the direction of the alternating current signal?

(2) Why are two signals of C_ADC and C_ADC1 input to the DSP? It seems that C_ADC1 is just a filtered signal of C_ADC.

Meanwhile, for phase B, only the B_ADC signal is input to the DSP. There is no B_ADC1 signal as uploaded below.

What is the reason?

Thank you for your consideration.

With regards,

GKIM