TIDA-01606: TMS320F28379D_LAB5

Part Number: TIDA-01606
Other Parts Discussed in Thread: OPA4350

hello:
I am currently running Experiment 5 with the following conditions: a 30 V three-phase input, no load, and the HV board is not connected. Whether I apply AC power or not, the waveform of
TINV_vGrid_A_sensed_pu never changes—it stays completely noisy. Measuring the OPA4350 op-amp output pin shows a steady 1.65 V with almost no variation. What is the most likely cause of this behavior?
thanks

  • And can you tell me why my TINV_vGridRms_A/B/C_sensed_Volts value is 0?

  • Hi,

    We have received your post and the investigation will take some time. Thank you for your patience.

  • 您好

    I'm not clear on which HW version you have. I assume it's rev E6 because of the OPA part number you mentioned.

    Was this HW from TI or did the customer build their own?

    You mentioned that the customer measured the op amp output with an oscilloscope and saw no output? even with 30Vac (phase voltage)?

    what about the lab 2 and 3, did they have it working?

    The first thing you need to do is to make sure you can see the difference amplifier working correctly with a scope.  The AC voltage measurement has 273:1 scaling factor (e.g. U18A).  So if you have 30Vrms phase voltage, the op amp should output  Vout = 1.65V +/- 0.155Vpk.  This has to work first and it should because it's just a basic difference op amp function.  If not, there is something wrong with the HW.  

    Another note is that the SW has a cutoff for measuring the AC input voltage (~50Vrms before it actually display the voltages in the watch window) 

  • I have solved this problem; it was indeed a hardware issue. Thank you for your answer.