Part Number: TMS320F28027F
Dear TI
I using 28027F with my own board. I found some difficulty when calibrating the current feedback. My measured the U and V phase current by using LEM current sensor. What I had done as below
1. User.h setting on the hardware parameters.
USER_IQ_FULL_SCALE_CURRENT_A (400.0)
USER_ADC_FULL_SCALE_CURRENT_A (800.0)
USER_NUM_CURRENT_SENSORS (2)
I_A_offset (0.9941855669) //value get from lab 3a
I_B_offset (1.00587225) //value get from lab 3a
2. Then I run lab 2b with motor, motor spin smooth and my clamp meter at motor side shows around 20A rms value.
3. Monitored the current feedback signal to the 28027MCU, which my hardware using A2, A7 as U and V phase current feedback. Signal shows the wave form as pic 1, seems ok.
4. Based on the calculation, (28A/ 400A ) *3.3V= 0.23V, so the wave should have around 460mV p-p. But my CCS Graph shows almost zero value, I also try to make scale between 0.1 to -0.1, also same.(Pic2)
5. In order to confirm on the CCS Graph buffer condition, I try to direct connect A2 to 3.3v and also to 0V. I observed that when connect to the 0v, The CCS graph will drop from 0 to -0.9v, But when I connect to 3.3v, the graph rises from 0v to ~0.2v only which expected value should be ~0.9V. Not sure why its like this. Both signal tested and same result. Can you advise what can cause this kind of issue? I feels more to software.
6. I searched online, some hit shows to run lab 3a, I tested and update the offset value, the current bias for both U and V phase almost the same around ~0.99.
Need your supporting and advise on my issue.
Pic 2
Pic 1.
