EVAL-M7-D111T + EVAL-M7-LVMOS-INV : My motor do not spin

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seb_44120
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Hello,

We bought the EVAL-M7-D111T + EVAL-M7-LVMOS-INV Combo and tried to spin a standard Brushless Motor.

Motor used is :  AXI 2814/10

 

Specifications in datasheet are :

No. of Pole : 14

Arms : 2,2A

Rated Speed : 1640 RPM/V (I try with 25V)

Line to Line Resistance : 36 mOhms

Line to Line Inductance : 6,6uH

 

We tried to configure parameters into MCE Wizard with these parameters :

Question 2 : 2,2 ARms

Question 3 : 14 poles

Question 4 : 0,018Ohms

Question 5 : 0.0033mH

Question 6 : 0.0033mH

Question 7 : 0.238 V/krpm (For this parameter, we measured with a scope : 0.1V peak to peak at 10Hz)

Question 8 : 2000RPM

Question 9 : 1000RPM

Question 10 : 1000RPM/sec

Question 11 : 0RPM/sec

Question 12 : 0sec

Question 13 : 100RPM

Question 14 : 50%

 

When I try to spin the motor into MCEDesigner, the motor vibrate but do not spin (this attached video).

Could you help me what parameters could I change ? is it the speed Loop  or the Current loop that need to be adjusted ?

What method to use ?

 

Thank you !
Sebastien

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Krupashankar
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Hi @seb_44120,

Krupashankar_0-1651121623417.png

According to the motor datasheet, we could find that the motor operating voltage range is 6-9V, but we noticed in MCE Wizard you have configured it for 20V-40V. Please correct us if we are wrong.

Can you tell us what is the DC bus voltage you are using? Please operate the motor in the operating voltage range mentioned in the datasheet.

 

Thanks,

Krupashankar

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Krupashankar
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Hi @seb_44120,

Based on the motor information you have shared:

Line to Line Resistance : 18 mOhms

Line to Line Inductance: 3.3uH 

For above values question  4 ( Phase resistance) :  0.5* ( Line to Line Resistance) = 0.009 Ohms

Question 5( Lq Inductance): Maximum line to line inductance * 0.5

Question 6( Ld Inductance): Minimum line to line inductance * 0.5

For measuring motor parameters you could refer to the document: How to Measure Motor Parameters

The power board parameters are also important for accurate current sensing, Please make sure if you have entered the correct parameters for Current Feedback based on the power board.

You could refer to the document: EVAL-M7-HVMOS-INV user guide 

Please make sure you have entered the correct parameters based on motor and power and try running the motor. 

Please let us know if this solves your issue if not  Could you please share your .mc2 file as a zipped attachment? 

 

Thanks,

Krupashankar

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Hi @Krupashankar !

Sorry for the mistake about Resistance : my Line to line resitance is 36mOhms so line to line resistance is 18mOhms. So Question 4 is : 0.5* ( Line to Line Resistance) = 0.018 Ohms

Same for Question 5 and 6 : my line to line inductance is 6,6uH so 3.3uH for question 5 and 6.

=> I update my post.

 

I just read your document about how to measure Parameters : I have one question :

-In your document the formula is : (Vpp/frequency)*Nbpoles*3.4

-In MCE Wizard, the formula is ((Vpp/(2*sqrt(6))/(120/(Nbpoles*Period)))*1000

=> One is twice more. Which equation is good ?

 

About power board parameters, I already updated them :

-Single shunt

-2000 kΩ for DC bus sensing high resistor 

-12.7 kΩ for DC bus sensing low resistor 

-68.8 mV/A for Motor current input scaling

-274 mV for Current input to ADC offset voltage

-1.23 A for Overcurrent trip level

 

See attached .mc2 file, could you check if I'm wrong on a parameter ?

Thank you for your help !

 

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Krupashankar
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Hi @seb_44120,

I just read your document about how to measure Parameters: I have one question :

-In your document the formula is : (Vpp/frequency)*Nbpoles*3.4

-In MCE Wizard, the formula is ((Vpp/(2*sqrt(6))/(120/(Nbpoles*Period)))*1000


Formula mentioned in MCE Wizard and Document is the same 

MCE Wizard : Ke =( Epk  * Number of poles * 1000)/ (sqrt(6) * frequency * 120) = (Epk* 8.33 * Number of poles) / ( sqrt(6) * frequency.

Parameter measurement Document : (Vpp * 8.33 * number of pole pairs ) /  sqrt(6) *frequency

One uses pole pairs and the other uses the number of poles in the calculation.

 

Could you please let us know what is the error you are getting when you try to run the motor?

 

Thanks,

Krupashankar

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Thank you @Krupashankar , I did not the see the difference beetwen the two formulas 😉

As I said in my first post, the motor do not run but only vibrate (did you see the attached video ?)

Maybe one parameter is wrong, but i do not find it...

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Krupashankar
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Hi @seb_44120,

Apologies for the delay in response as we had long holidays.

Based on your .mc2 file we have few suggestion 

  • Ques 11 Open Loop Speed Ramp Rate - Try varying this value from 100 RPM/sec - 300 RPM/sec
  • Ques 15 Initial Angle Sensing - Enable 
  • Ques 9 Minimum Running Speed - Try Reducing this value ( 200 RPM - 400 RPM)
  • Ques 60 Flux Estimator Time Constant - Your motor's L/R ratio is too low try reducing the flux estimator time constant to 3-5 mSec

Please make these changes in parameter file and see if it resolves your problem.

 

Thanks,

Krupashankar

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Hi @Krupashankar !

Thank you for your response (I was also in holidays this week 😁 )

I applied parameters you told me.

With your parameters, the motor did not turn.

So I tried to change parameter one by one.

 

=> With this configuration, motor start to spin !  (but stop after few seconds, this attached video 😞

  • Ques 11 Open Loop Speed Ramp Rate : 100 RPM
  • Ques 15 Initial Angle Sensing : DISBALE
  • Ques 9 Minimum Running Speed : 300 RPM
  • Ques 60 Flux Estimator Time Constant : 5 mSec
  • I Also changed the Motor Rated Ramps to 10 ARms !

 

After 4-5 running test, the motor get moderately hot.

 

Traces are useful to see parameters changes, but I don't know what is the procedure to understand by myself wich parameters I have to adjust.

 

I notice some strange behaviors :

1. When I see that motor turned off, I note the RPM speed and write the "target speed" below but the motor do not stop at this speed.

2. The speed ramp rate is set to 300 RPM/sec in configuration file, but the acceleration is really slow (like 20RPM). Is it normal ?

 

Could you continue to help me to investigate my problem ?

Thank you in advance ! 👍

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Krupashankar
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Hi @seb_44120,

Could you please share the latest .mc2 file? 

What is the error you are getting in MCE designer when the motor is stopped?

 

Thanks,

Krupashankar

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Hi @Krupashankar ,

See attached the latest .mc2 file.

 

When the motor stop to spin, it has small vibrations (like the board continues to drive the motor, but timing are wrong).  MCE Designer do not show errors (see screenshot).

 

seb_44120_0-1651000907940.png

 

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In addition to my last post, i would like to add some information.

I tried to change the "Minimum Running Speed" (Question 9)

 

-When I set it to 1000RPM : the motor spin to 300RPM and stop.

-When I set it to 500RPM: the motor spin to150RPM and stop.

See the picture below.

seb_44120_0-1651092880409.png

 

 

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Krupashankar
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500 replies posted 50 likes received 25 likes received

Hi @seb_44120,

Krupashankar_0-1651121623417.png

According to the motor datasheet, we could find that the motor operating voltage range is 6-9V, but we noticed in MCE Wizard you have configured it for 20V-40V. Please correct us if we are wrong.

Can you tell us what is the DC bus voltage you are using? Please operate the motor in the operating voltage range mentioned in the datasheet.

 

Thanks,

Krupashankar

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Thank you @Krupashankar  !!

You are right ! The motor's specifications said that the motor has an operating voltage range of 6-9V.

But I thought that spinning it whithout propeller, I could put a voltage of 25V... Apparently not (even if it spin up to 300RPM).

 

So I tried with another motor I have (QBL4208-41-04-006 which is done for a 24V voltage) : And it's working on first try ! 👍

 

Thank you for your support. We can close this thread !

My final motor application is not with this motor : I will open another thread if I have problems.

 

Thank you again for your help @Krupashankar , you solved the issue !

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