CCS/TMS320F28335: FOC of PMSM - Distorted Inverter Current Waveform

Georgy Joseph

Part Number: TMS320F28335

Tool/software: Code Composer Studio

Sir,

We are using TMS320F28335 DSP board with CCS 6.0.0 for the FOC of PMSM with specification - 75VDC, 8000RPM.

We are implementing FOC of PMSM on the basis of the pdfs http://www.ti.com/lit/an/sprabz0/sprabz0.pdf and http://www.ti.com/lit/an/sprabq3/sprabq3.pdf.

1. We have done the first level incremental build of FOC as per the pdf with our motor specifications, we have got the SVPWM output on the CRO and verified with the above pdfs. But can you please tell the settings needed for getting the waveform outputs on the watch window as shown in the pdfs?

2. We just tried the second level incremental build of FOC as per the pdf to run the motor at 400rpm by giving 25VDC. But, the current feedback we got from the CRO is having distortions at the peak points. I have attached its image with this. Can you please help us to find out what is the error?

over 5 years ago

0 Ramesh Ramamoorthy over 5 years ago

TI__Mastermind 27240 points

1. The SVPWM output will be pulses at carrier frequency. The graphs shown are the pulse width values and not the physical pulses. This is done by utilizing the graph utility. From within the debug perspective, click Tools --> Graph --> DualTime, then click import. browse to graph1.graphprop in the project directory and you should be able to see the graph.
2. Second incremental build is open loop control of motor, done for verifying / calibrating the feedback signals. If the current waveform is so ripple infested, it is because the motor inductance is too small for the switching frequency. If your application cannot accept this much ripple in current, then you will have to increase the switching frequency.

0 Georgy Joseph over 5 years ago in reply to Ramesh Ramamoorthy

Prodigy 210 points

Thank You for your valuable reply sir

We are doing our project by taking the reference from the pdfs I have mentioned earlier. We have included the D log file also.

1. As per the direction, We have taken out the below SVPWM output graph on the watch window. Can you please suggest any measures to rectify the error?

0 Ramesh Ramamoorthy over 5 years ago in reply to Georgy Joseph

TI__Mastermind 27240 points

Set graph properties per attached pic

0 Ramesh Ramamoorthy over 5 years ago in reply to Ramesh Ramamoorthy

TI__Mastermind 27240 points

pic attached now

0 Georgy Joseph over 5 years ago in reply to Ramesh Ramamoorthy

Prodigy 210 points

Thank You so much Sir for your valuable suggestions

We got the graph as shown below.

How can I convert the current Y-axis value (_iq value(_iq24)) to a floating point value?

0 Ramesh Ramamoorthy over 5 years ago in reply to Georgy Joseph

TI__Mastermind 27240 points

The graph tool receives the data as 16 bit signed, so you may select the 'Dsp Data Type' as '16bit signed integer'. I don't think it can be plotted as float. Pls review the data type of the variable (DlogCh1/2/3/4) that is used to send data to the graph function. Hope it helps.

0 Georgy Joseph over 5 years ago in reply to Ramesh Ramamoorthy

Prodigy 210 points

Thank You sir for your valuable reply.

Sir,

How to view a continuous running waveform so that we can notice the change in real time ?

0 Ramesh Ramamoorthy over 5 years ago in reply to Georgy Joseph

TI__Mastermind 27240 points

you need to refresh the graph plot to see the next set of data points. Review the command icons within the graph window by hovering over each of them and you will know.

0 Georgy Joseph over 5 years ago in reply to Ramesh Ramamoorthy

Prodigy 210 points

Sir,

As per your instruction, we have refreshed the graph plot, but still we didn't find any incremental changes in the x axis.

The DLOG_4CH_buff1 access data from DlogCh2. What is to be done to access the data from DlogCh1?

0 Ramesh Ramamoorthy over 5 years ago in reply to Georgy Joseph

TI__Mastermind 27240 points

You should notice the x axis value count keep on changing. If not, you need to refresh. If it does not change, I don't know what to tell because I have not seen it.

Change the start address to DLOG_4CH_buff2 if you want to change the plot.

0 Georgy Joseph over 5 years ago in reply to Ramesh Ramamoorthy

Prodigy 210 points

Sir,

The above mentioned are the details of the graph and the graph output.We noticed that the x axis value count keep on changing (marked inside the red box in the graph output). But we are not able to view rest of the graphs.

The variable represents the plot gives a range of values upto 2400, but why we are getting high Y-axis values(as shown in the figure) on the graph?.

0 Ramesh Ramamoorthy over 5 years ago in reply to Georgy Joseph

TI__Mastermind 27240 points

Refer to e2e.ti.com/.../796995

Also, I suggest you to spend some time intuitively varying settings in this window to study. Support through e2e will take more time. Research and review the information available in e2e to speed up your work.

0 Georgy Joseph over 5 years ago in reply to Ramesh Ramamoorthy

Prodigy 210 points

Sir,

We are not able to set the range of Y-axis, so we searched for some solution and got the graph characteristics from the ti forum, which has the provision for setting the Maximum and Minimum value of Y-axis as shown in figure above. But in CCS V 6.0.0, this feature is not available, is there any alternative to set the range of Y-axis in this version?

0 Richard Poley over 5 years ago in reply to Georgy Joseph

TI__Mastermind 27200 points

Open the graph, then right-click on the y-axis and un-check "Auto Scale". Then click the "Show the Graph Properties" button in the graph window. The max and min Y axis entries will appear.

Regards,

Richard

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CCS/TMS320F28335: FOC of PMSM - Distorted Inverter Current Waveform