MCF8316AEVM: Increase starting torque

Hi Thilo Foster,

There are few parameters which need to be configured 

1. Open Loop Acceleration A1, A2 should be chosen properly for motor inertia

2. Open Loop current Limit - OILIMIT has to be appropriate but consider not to exceed rating of motor. General half the rated value can be used.

Can you share current rating and voltage rating of the motor? 

I will be able to reply early next week.

Thanks and Best Regards

Venkatadri S

Hi,

I've already tried increasing the open loop current limit but increasing the acceleration finally led to some changes. The pump is still not turning, but it seems to be close to the threshold.

These are the motor specifications:

Hi Thilo,

Thanks for sharing data, I will provide a basic JSON with setup instructions.

Thanks and Best Regards,

Venkatadri S

Hi Thilo,

I am adding JSON in the end, I have assumed the Resistance and Inductance are phase to phase and hence I have divided them by 2 to match for Per Phase and programmed it.

If this is not proper we can run MPET. 

Details of reference JSON

1. Motor Parameters: R, L I have populated with the values you have provided, and KE is 0, we need to run the MPET to measure this
2. Current Limits: I have set Fault triggers to 5A, if any phase current peak exceeds 5A at any point motor will stop driving- The device is configured for retry after 5 seconds
3. Max speed: I have put 200Hz as max speed (3000 rpm for 4 pole pair), at no Load if Voltage is adequate, we should see 200HZ for full speed command

Procedure

1. Load the attached JSON
2. Goto MPET Tab and enable "Measure Motor Resistance", "Measure Motor Inductance" and “Measure Motor BEMF Constant” and do not enable  “Measure Motor Mechanical Parameter “ 
3. After step 2 is successful, enable “Measure Motor Mechanical Parameter “ to complete speed loop tuning.

Hi,

thank you. I won't get back to it until next week and will report back then.

Best regards

Thilo

Hi Thilo,

Sure, please let me know when you are able to test

Thanks and Best Regards 

Venkatadri S 

Hi,

I have configured the motor as suggested but it still does not run with the tube installed. Editing OILIMIT and the acceleration still does not help.

Probably the torque of the motor is not enough. I thought so since I first tried to configure the motor, but my supervisor (with more experience in this area) said that the motor should actually be strong enough, as it has more power than the previous one.
Is there anything else I can try or do you also think that the torque is not enough?

Thank you and best regards

Thilo

Hi Thilo,

Did you run MPET for KE measurement?  Better to run MEPT KE without load so that motor can spin with good kinetic energy while coasting down.

Can you share your JSON again after MPET ?

Thanks and Best Regards 

Venkatadri S 

Yes, I had run MPET without load but I have just realized that I forgot to save the results. Now when I set OL_ACC_A2 to 5Hz/s2, OL_ACC_A1 to 10Hz/s and OL_ILIMIT to 5A, the pump turns 3-4 turns and then it stops. So it seems the motor needs to much current to turn the pumphead.

Here the JSON after MPET:

Hi Thilo,

I am out of office tomorrow, I will aim to respond by week end .

Thanks and Best Regards

Venkatadri S

Hello,

have you already had the opportunity to look at this?

Hi Thilo,

Thanks for reminding, I have not looked into this.

Kindly wait for a day, I will reply to this.

Thanks and Best Regards

Venkatadri S

Hi,

have you had time to look at it again in the meantime?

Hi Thilo,

I have made some changes again. 

I made following changes

1. I increased the current limit in close loop since your load may need up to 5A, I increased to 4A only.

2. Disabled the speed loop, motor runs only in current loop, the speed command filed 0 to 100% in this mode corresponds to 0 to 100% torque which 0 to 4A. The current limit (ILIMIT) is per phase peak value not the DC bus current

Try with 30% command first and let me know .

Hi,

thank you. On the first try it did not work, but when I increase closed and open loop ILIMIT to 4.5A the motor manages to turn the pump and then immediately stops without any fault.

Best regards

Thilo

Hi Thilo,

Please enable abnormal BEMF fault, reduce the BEMF threshold value .

If motor is stopping without any fault, there may be driver related fault also.

Can you confirm device part number, MCF8316A  or MCF8316C?

Thanks and Best Regards

Venkatadri S

It's a MCF8316A but the MotorStudio software detects it as MCF8316C and I can't change it.

Hi Thilo,

That is strange, can you check Motor studio version? 

Also, please try to check Marking on the device.

Thanks and Best Regards

Venkatadri S

Motorstudio version: 0.1.18

On the board is printed MCF8316AEVM Rev 2.0 MD038A-001

and below is a sticker with MCF8316C1VQRGFRQ1

Hi Thilo,

Is it possible to take image (part marking) and share me.

In case if you have received wrong device we want to verify and take corrective step.

Thanks and Best Regards

Venkatadri S

Yes, of course:

Hi Thilo,

I want some clear image of IC (marking on the IC), can you send me that.

Thanks and Best Regards

Venkatadri S

This is the best picture I could take:

Hi Thilo,

Thank you, this is MCF8316C device very clear.

Can you confirm MOTOR STUDIO version? Hope it is latest downloaded from TI.COM.

Can you show the motor studio main page after device is detected?

Thanks and Best Regards

Venkatadri S

Yes, the Motorstudio version is 0.1.18.

What is the difference between MCF8316C and MCF8316A?

Hi Thilo,

MCF8316C is improved version of MCF8316A.

Example, MCF8316A had limited bandwidth for communication while motor is running.

Please refer to this link for more details (+) [FAQ] Production device information - Motor drivers forum - Motor drivers - TI E2E support forums

Also, main difference is as shown in the image below.

Thanks and Best Regards

Venkatadri S

Thank you.
We will soon receive another motor with more torque and check if it works then.