Odd clarke1.Alpha and clarke1.Beta waveforms in Sensorless FOC PMSM Build 2

I am not familiar with this code but it looks like your Clarke module is not getting the correct input ... please check your inout to Clarke module ... the clarke module should receive a balanced sinusoidal waveform ....

Hi Arefeen,

That is the input to the Clarke module.

Sorry .. what is the input? Your code post doesnt show Clarke section or am I missing it somehow?

Sorry.  I meant the clarke1.Alpha and clarke1.Beta signals are the inputs to the clarke module.  The clarke module takes in alpha and beta and puts out d and q.  The two bottom wavy looking sine wave signals are my alpha and beta.  I think something is wrong.  I think those are my phase a and phase b currents.

My boss just came in (he does motors) and said this current waveform could be because of how we wind the motor.  Of course, the motor isn't turning during this stage of the build.  Does anyone know if this is normal for some motors? 

May be our convention is opposite but if you look at TI documentation then As and Bs are the inputs to Clarke module (As and Bs are basically phase A & B of a three phase system) and the outputs are Alpha and Beta which are 90 degrees phase shifted ... if your inputs have harmonics then your time varying orthogonal outputs (alpha and beta) will also have harmonics. So, if your putting currents with harmonics then your Alpha and Beta will also have harmonics. By the way, we are currently developing systems using these blocks and so far we haven't experienced any bugs.....

Your current values look "wonky" (I think that's the technical term)

What speed are you running?

Check your analog sense circuits.

Hi Arefeen,

I think my understanding is just a little off.  The documents said the clarke1.Alpha waveform should be the same as the clarke1.As waveform.  I think I misread that statement as being they were the same signal. 

Here are the clarke1.As and .Bs waveforms (bottom 2).  As you can see, little has changed.  I'm also trying to digest  the other comment above about my signal being wonky.  If I can get 10 minutes peace in my office I'll look at that next. 

Incidentally, I backdrove my motor with a drill and looked at my phaseA to phaseC voltage on a scope.  It's not a perfect sinusoid but it definitely is far more sinusoidal than the current waveforms below.

Hi Chris,

I think your technical term is pretty accurate.  I wish I knew what was causing it.

It doesn't matter if I'm running at 0 RPM or 1000 RPM.  It does get a little better at 2000 RPM but it's still wobbly.  I'm not going faster than that yet because I'm still at build level 2.

Just for the record, I'm running the high voltage kit at 28V (external power supply).  I was told by my representatives that this was not a problem. 

I just checked the current waveforms at Ifb-U and Ifb-V on the PCB in the kit.  This waveform looks the same (but with a lot more noise).  Of course, it looks a lot like the svgen_dq1.Ta above too.

  what hardware are you using?

the current signal doesn't look good. could be an issue with the board, or could be something in the A/D sampling.

Hi Chris,

I'm using the HV Motor controller development kit with the TMS320F28035 processor.  I think I know what is going on.  I'm running a 28V motor and my voltage feedback is too small because the kit is expecting a 200V motor.  I'm going to change out the feedback resistor divider such that I have 1.65V @ 28V input and see if that helps.

Yes, this will be your issue I bet. We are updating the hardware with a better, more flexible current sense circuit.

Hi Richard,

I have the same problem. It might be the motor itself. How it is wound, etc. I am using BLDC hub motor with concentric winding (not distributed winding). However, the back-EMF is perfect sinewave. I expected it to run sinusoidally very well, but I got the same current waveforms as yours at Build 2. I don't know exactly what causing it, but it seems like the way the motor is wound causing this issue. Do you have any improvements of the current waveforms so far? Thanks.

Baris