TIDM-1000: C2000 microcontrollers forum

Roberto,

I cannot access the images, but some variation may be expected. Are you using the ADC sensing option or the SDFM for the currents?

-Manish 

Hi Manish,

Thank you for reply.

I tried boths, the ADC sensing and the SDFM for the current.

When i use SDFM the THD is worst than the ADC. THDs are about 7% for L1 and L2 and 10% for L3 (Build 3).

I post photos.

Could it be a measurement noise problem?

- Roberto

I will recommend doing the measurements under Build 4, that is the one we used to document all the performance metrics. I do know the ADC distortion is slightly higher on Phase 3 but i will like to see how your measurements look like in build 3. 

It has been a very long time since i ran this design, but with SDFM you should see better current sense quality and better performance.  

1. Please share waveform for build level 4

2. You can also probe the Vac sensed in the graph window,  any distortion in Vac will come up as distortion on the AC output

VIENNA_dVal1 = VIENNA_guiV1_Volts;
VIENNA_dVal2 = VIENNA_guiV2_Volts;
VIENNA_dVal3 = VIENNA_guiV3_Volts;
VIENNA_dVal4 = VIENNA_iL3Meas_pu;

DLOG_4CH_run(&VIENNA_dLog1);

steps to load the graphs are in UG 6.4.1.3 Setup Debug Environment Windows, section 2

you will need to import both the graph files to see all the 4 variables..

-Manish 

I note on the schematic two ways of measuring line current, Hall sensors and shunt resistors.

I also see in this thread reference to the ADC or SDFM methods.  It appears the ADC refers to the hardware ADCs and the shunt resistors.  What does SDFM stand for?

Is there a software switch to use one or the other?

Why two methods for measuring current?

I couldn't find anything in the user manual about this.  Is there another document I'm missing?

Hi Manish,

They are the photos for build 4:

                  Build 4 with ADC sensors (Vin = 120Vrms, 500ohm Load)

                        Build 4 with SDFM current sensors (Vin = 120Vrms, 500ohm Load)

I think the problem is the noise of the IL3 ADC current measure because if i set Build 1 (current loop only) i have the following measures:

Build 1 - Kpi =2 (Vin 120Vrms, Load 500ohm, iRef=1.65)

with the same condition i have the following Sfra and Current measurement

 Build 1  SFRA - Kpi =2 (Vin 120Vrms, Load 500ohm, iRef=1.65)

 Build 1  IL3

Build 1 - IL2 (IL1 is similar)

Thank you

Ok, I watched video - SDFM is sigma delta - doh!

I will start a new thread with questions about current sensing.

Jeff, 

In the above, did you also check the voltage sensing? we multiply the voltage with the current ref from the outer bus voltage loop. If there is noise on it we will be also adding to the distortion. 

On our end we did not see it to be this bad and SDFM was always very clean and better THD. 

-Manish