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Motor Control ICs Forum Discussions

AsadBashir160
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Hi, I'm working on Invertor compressor using EVAL-M1-CTF620N3 controller board with EVAL-M1-101T-F048 controller. I have read manuals for both controller board and controller as well as EVAL-M1-IM535. But now I'm stuck. I want to make Flux_M in "Iu & Flux_M oscilloscope" DC like but I don't know which parameter is effecting it. I tried the parameters as said in manual, quote below:

13. Set target speed to about 50% of MAX speed, start “Iu & Flx_M” trace with “Auto Repeat On Level,” see
Figure 10. Flx_M is better within the range of 2000~2500 (rated value is 2048), and MUST be steady and DClike.
Some key tips for better motor-performance tuning:
• If Flx_M is not steady (swinging or oscillating), double-check motor parameters, speed loop PI gain, flux Estimator
time constant and PLL PI bandwidth (parameters PLLKp & PLLKi) related setup.
• If Flx_M is very noisy, double-check current feedback and Vdc-related hardware and parameters.
• If Flx_M is far from 2048, “Motor Back EMF Constant (Ke)” needs to be adjusted in MCE Wizard.

 

AsadBashir160_0-1671272398648.png

 

Now, I've already brought my Flux_M b/w 2000 to 2500, but there's still noise in it. Following is my waveform.

AsadBashir160_1-1671272479561.png

 

Now, as it's mentioned in manual to change "PLL PI bandwidth (parameters PLLKp & PLLKi) related setup" but the problem is that the MCE Wizard 2.3.0 version that I'm using doesn't have a PLLKp or PLLKi parameter or PLL PI Bandwidth for that matter. The only parameter with PLL is in "Fault Conditions" which I believe will not work in my case. 

AsadBashir160_2-1671272725329.png

 

So, that's why I want help. Please help me clear my confusion and please mention if I've missed something.

Thanks. I'll be waiting for your guidance.

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1 Solution
Krupashankar
Moderator
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250 replies posted 100 solutions authored 5 likes given

Hi @AsadBashir160,

  1. The motor takes a higher current at the starting stage. We would recommend increasing the current limit.  Can you please try changing the following parameters Ques 13: Low Speed Threshold = 1000 RPM Ques 14 : Low Speed Current Limit - 60% and observe if the vibration is reduced.
  2.  CPU load can go up to 70-80% so you can try increasing the PWM frequency.
  3. Happy to hear that you were able to fix the variation in Flx_M.
  4. The motor speed variation can be controlled by tuning the Kp and Ki values Please try changing the following parameters Ques  62 : Speed regulator Proportional gain and Ques  63 : Speed regulator Integral gain

 

Thanks,

Krupashankar

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15 Replies
Krupashankar
Moderator
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250 replies posted 100 solutions authored 5 likes given

Hi @AsadBashir160,

For getting a DC like Flux_M motor parameters have to be measured and entered accurately in MCE Wizard for measuring the motor parameters please refer to document : How to Measure Motor Parameters 

PLLKp and PLLKi are dynamic parameters and can be modified using MCE Designer or through a script. For more details on scripting please refer to : How to Use iMOTION™ Script Language 

Please let us know if any further details are required.

 

Thanks,

Krupashankar

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AsadBashir160
Level 1
Level 1
10 replies posted 10 sign-ins 5 replies posted

Hi @Krupashankar,

My motor parameters are accurate to the best of my knowledge. Following are the parameters provided to me by the manufacturer in the datasheet.

AsadBashir160_1-1671436530897.jpeg

 

AsadBashir160_0-1671436509485.jpeg

Now, here Ke is in line-line; but in MCE Wizard we require neutral-line. So I converted it using formula "line-neutral = (line-line)/1.732 ".

As for resistance, I'm using "DC Bus High Resistor = 2000 kOhms" and "DC Bus Low Resistor = 13.3 kOhms". Inductance is also provided by manufacturer in the datasheet.

AsadBashir160_2-1671436846708.png

So @Krupashankar, Please have a look at this and do inform me if I've made a mistake somewhere.

As for PLLKp and PLLKi, I'll go through the file that you shared and will get in touch with you later if needed.

Thanks;

AsadBashir160

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Hi @Krupashankar,

I looked into PLLKp and PLLKi parameters but all they did was increase the Amperes. 

So, what do you think the problem is ? Can you help me out in this ?

Thanks,

AsadBashir160

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Krupashankar
Moderator
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250 replies posted 100 solutions authored 5 likes given

Hi @AsadBashir160,

Can you please share the complete motor datasheet and MCE Wizard file ( .mc2)?

This will help us to find if there is any difference in parameter configuration.

Flx_M may have slight oscillations due to rotor saliency and other motor deviations.

 

Thanks,

Krupashankar

 

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Hi @Krupashankar,

Thank you for your reply.

Sure I'll attach both files. PDF file is the datasheet file.

Regards,

AsadBashir160

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Krupashankar
Moderator
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250 replies posted 100 solutions authored 5 likes given

Hi @AsadBashir160,

We have compared the motor datasheet and MCE wizard configuration file. The motor parameter configuration looks correct.

We could see that current is limited to 20% of rated current up to 7000 RPM according to the .mc2 file you have shared. Is this operation intended?

Can you please try increasing the Ques 58 - current regulator bandwidth ? and check the Flx_m.

We could see that sensorless control is enabled this can also cause slight deviation in Flx_M and Flx_M may have slight oscillations due to rotor saliency and other motor deviations.

Can you please tell us if there is any performance deviations due to Flx_M variation?

 

Thanks,

Krupashankar

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Hi @Krupashankar,

Thank you for your reply.

For the first part where you asked about 20% rated current, I'd say yes it was intended because I want a smooth motor start.

As for Ques 58, I will test that and will get back to you.

As for sensorless control, yes I have enabled sensorless configuration because I'm using Brushless Compressor (sensorless FOC). So in my case I have no use for sensor.

Regards,

AsadBashir160

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Hi @Krupashankar,

Like you said, I tested Ques 58 parameter. But it had no significant effect on Flux_M. Instead after reaching 1300 rad/sec, if I increase it a little bit more (for example 1500 rad/sec) than my motor suddenly shut down.

Regards,

AsadBashir160

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Krupashankar
Moderator
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250 replies posted 100 solutions authored 5 likes given

Hi @AsadBashir160 ,

Flx_M may have slight oscillations due to rotor saliency and other motor deviations.

Can you please tell us if there is any performance deviations due to Flx_M variation and if there is any specific application need which demands constant Flx_M?

 

Thanks,

Krupashankar

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Hi @Krupashankar,

Thank you for your reply.

The only effect on the performance that i noticed so far is that when compressor starts it produces an unusual sound and vibrates at that time, than it become stable after 1.5 mins. But the noise still remains.

The only way I can explain the noise is that it's a high pitched noise which is irritating.

As far as I know Flx_M represents "the flux of permanent magnet of the motor". This means it is effected by the torque of the motor. I believe that there's some kind of unstability in compressor motor running which is causing this. The vibration at the start of compressor running explains this as well. Atleast that's what I think.

So, that's why I believe that if Flx_M gets stable it'll resolve that motor unstability issue. Please do correct me if you think I'm wrong somewhere.

Thanks,

AsadBashir160

 

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Krupashankar
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250 replies posted 100 solutions authored 5 likes given

Hi @AsadBashir160,

Sorry for the delayed response due to the year-end vacation and Happy New Year!

Initial vibration at the time of start can be due to the limitation in the initial starting current, can you tell what is the RPM at which the motor becomes stable?

High pitched noise can arise due to low PWM frequency.

Can you please try changing the flux estimator time constant to 3 msec? and share the result with us.

 

Thanks,

Krupashankar

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Hi @Krupashankar,

Thank you for your reply.

Regarding vibration I don't get what you said about "limitation in the initial starting current". Isn't that what we want while working on inverter !? Don't we need our inverter system to consume less current at the start of the system !? If what you say is true than does that mean I should expect vibration at the start ? But I'm also working / testing on another inverter card and it doesn't provide me any vibration at all. 

About RPM that you asked, I think the compressor gets stable at around 2200 RPM (4700 to 5700 counts).

As far as PWM Frequency and high pitched noise goes, you are absolutely right about that. They are connected. I've known this for a while now but the reason I'm not touching that parameter is because the more I increase PWM Frequency; the more CPU load increases. So, I'm not really sure whether it's a good idea to increase CPU Load. Right now I'm using 6kHz PWM Frequency. But if I increase it to >10kHz than CPU also increases. I've also noticed that increasing PWM frequency gives a bit stable Flx_M. But I can't take it further than 22kHz. You can see it below.

AsadBashir160_0-1672731253409.pngAsadBashir160_1-1672731307469.png

As you asked me to bring down "Flux Estimator Time constant" to 3msec, I tried that but it was giving me error.

AsadBashir160_2-1672731468573.png

So, I was just testing to see how can I remove this error. While testing I figured that if I increase PWM frequency to 16kHz than I can remove this error so I did that. Following was the result at (PWM Frequency = 16kHz) and (Flux Estimator Time Constant = 2msec).

AsadBashir160_3-1672731774258.png

Fortunately, my Flx_M has gotten a lot better now. Although the vibration is still a problem.

There is one more thing that's bugging me and that is "Motorspeed". RPM waveform is still not stable.

AsadBashir160_4-1672731884395.png

Thanks,

AsadBashir160

 

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Krupashankar
Moderator
Moderator
Moderator
250 replies posted 100 solutions authored 5 likes given

Hi @AsadBashir160,

  1. The motor takes a higher current at the starting stage. We would recommend increasing the current limit.  Can you please try changing the following parameters Ques 13: Low Speed Threshold = 1000 RPM Ques 14 : Low Speed Current Limit - 60% and observe if the vibration is reduced.
  2.  CPU load can go up to 70-80% so you can try increasing the PWM frequency.
  3. Happy to hear that you were able to fix the variation in Flx_M.
  4. The motor speed variation can be controlled by tuning the Kp and Ki values Please try changing the following parameters Ques  62 : Speed regulator Proportional gain and Ques  63 : Speed regulator Integral gain

 

Thanks,

Krupashankar

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Hi @Krupashankar,

Thank you for your reply.

Ok sure. Please give me some time to test this. I'll reply as soon as I get the results.

Thanks,

AsadBashir160

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Hi @Krupashankar,

Sorry for the late reply. I'm working on two different projects that's why it took me a while to test what you suggested.

I tested those parameters which you mentioned but neither the vibration is going down nor the RPM waveform is getting better.

Thanks,

AsadBashir160

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