MCF8316AEVM: Cannot start spinning the motor

Hi Tommy,

Can you confirm whether EVM is recently bought , because we have replaced MCG8316A with MCF8316C .

You can also download new GUI motor studio available on ti.com

Please confirm on these two questions, I will get back to you after 2nd .

Thanks and Best Regards 

Venkatadri S 

Yes, the EVM is recently bought. It seems that the driver IC is MCF8316C from the chip marking. So I should use another GUI instead of the one mentioned in the quick start guide?

Hi Tommy, 

Yes use new GUI , link is available in the product landing page.

We have created quick start guide, we will share the draft by next week after we return. 

Thanks and Best Regards 

Venkatadri S 

Hi,

I tried with the motor studio as I assumed to be, and followed the guide to tune and spin the motor. In the tuning phase, the following error comes out:

17:37:35:616 | : Fault detected : CONTROLLER_FAULT,ABN_BEMF,MTR_LCK

17:37:35:479 | : Could not detect any MPET fault. Please check the tuning file..

17:37:35:449 | : Motor ke measurement error...checking for faults.

17:37:1:403 | :Beginning Motor Ke measurement...(Your motor will spin up slowly during this time)

17:37:1:402 | :Motor R and L measurement complete

17:37:0:291 | :Beginning Motor R and L measurement...

17:36:58:890 | : Running MPET...

I am not sure how should I start. I am confused about the "load default" session, is there a sample default json to start tuning?

Hi Tommy,

Can you provide motor spec? Max speed in RPM and pole pair, max current

If you know R and L per phase also good otherwise, we will use MPET.

What is the motor type? Is it Fan?

Thanks and Best Regards 

Venkatadri S 

Hi,

The motor used is FL42BLB02 - www.fullingmotor.com/.../58_93

The motor max speed is 3000rpm with 3 pole pairs, max current is 8.5A.

Hi Tommy,

I hope you have latest Motor studio 0.1.22 which is available for downloading.

We also created a E2E where we keep updating the reference JSON files. 

You can pick a JSON which is closer to the current rating Equipment type (Fan/Pump/actuator etc) and run MPET to measure R, L, KE for your motor.

Link for E2E (+) [FAQ] MCF8316C-Q1: Spinning BLDC motors with Motor Studio - default JSON files for different specifications - Motor drivers forum - Motor drivers - TI E2E support forums

Use the JSON as default load and then run MPET.

Please try this method and let me know if you face any issue.

Also, start with lower current  (may be 1/3 of rated current which can be basic minimum required to spin the motor and not the max load condition) and then increase current until you get familiar with configuration and motor.

Thanks and Best Regards 

Venkatadri S 

Hi,

I tried loading the JSON files from the link but it reports invalid file.

Btw, I tried using the JSON dumped from the old MCF8316A GUI, which let me goes to the second part to run the MPET. However, it always results in fault during BEMF measurement.

10:18:45:668 | : Fault detected : CONTROLLER_FAULT,ABN_BEMF,MTR_LCK

10:18:43:35 | :Beginning Motor Ke measurement...(Your motor will spin up slowly during this time)

10:18:43:35 | :Motor R and L measurement complete

10:18:42:530 | :Beginning Motor R and L measurement...

10:18:39:4 | : Running MPET...

10:18:30:118 | : Default register settings loaded.

Hi Tommy,

The JSON downloaded will have extensions which we need to rename with simple "name.JSON". 

Example Default.JSON.

After this do not run MPET from quick spin tab instead goto MPET Tab.

Reason is for some motor running MPET KE and MECH together will not work due to intertia variations.

Hence, select only KE and then run the MPET.

After KE is completed we can run MECH.

Follow below tuning tips for KE

And then for Mechanical

Thanks and Best Regards 

Venkatadri S 

Hi,

Thanks for the guide, I followed the steps mentioned to measure the BEMF, and the fault still pops out during the process.

Hi Tommy,

Make sure you follow configurations are proper after taking care of the steps mentioned above

1. Max speed information 

2, Disable Auto hand off

3. Configure open loop to closed loop hand off to 35% so that motor can spin to generate adequate BEMF

4. Is your motor inertia is too low? 

5. In the ISD CONFIG register there is STAT_DET_THR , reduce the minimum BEFM value to the lowest (50mV)

Thanks and Best Regards 

Venkatadri S 

Hi,

1. My max speed is 3000rpm with 3 pole pairs, so in conversion should be 150Hz. Please correct me if I am wrong.

2. Where can I find this setting?

3. I set the Open Loop speed reference to 35%, I guess that one is the handoff threshold as mentioned.

4. I am using a bare motor with no load on the shaft, but I guess the load is not needed for tuning?

5. Yes, I have checked the register map and this is already set.

Thank you very much.

Tommy

Hi Tommy,

1. Yes correct

2. You can got Motor parameter tab in all tuning page and enter max speed. Please confirm if you are able to locate it.

3. Yes correct, this speed is open loop to closed loop hand off threshold point.

4. For speed loop we need load, for R, L, KE we do not need. Infact, KE measurement will be easy without load since rotor will coast for longer.

Thanks and Best Regards 

Venkatadri S 

Hi,

I still immediately get faults and fail in KE measurement. I actually saw it starts spinning the motor but the measurement fails. Why is that?

Thank you.

Tommy

Hi Tommy,

What is the type of load?

Can you prove speed/FG pin or phase voltage and measure how long the rotor is coasting?

If inertia is too low motor may stop faster and BEMF measurement may not be possible and hence I suggest for spinning motor for higher speed in open loop so that motor can acquire some good Kinetic energy and coast for some time.

Thanks and Best Regards 

Venkatadri S 

Hi,

I can see speed pin with 3.3V signal and pulses with increasing frequency when the motor start spinning.

I tried using 50% as open loop speed reference but the result is same. Currently I didn't put any load on the motor.

Btw, may I know what the faults shown on the right panel represents?

Thank you.

Tommy

Hi Tommy,

The fault ABN_BMEF is abnormal BEMF which is one of the motor lock and hence MTR_LOCK flag also sets. The MTR_LCK belongs to controller fault category and hence CONTROLLER_FAULT flag is also sent.

I don't think we need to run up to 50%, I recommend 35% which is generally adequate.

I suspect max speed information wrong.

Please post the JSON file.

Thanks and Best Regards 

Venkatadri S 

Hi,

I am inputting the information from the motor datasheet and running MPET so I guess JSON file does not relate?

Anyway, just in case, which JSON should I share?

Thank you.

Tommy

Hi Tommy,

Can we do a quick test instead of doing trial and error like this.

If MPET is failing, then we will do manual measurement

To do that

1. Use voltage probe across two winding (don't connect motor to EVM / PCB)

2. Hand spin the rotor, we will see sinusoidal voltage 

3, Chose one wave (which is reasonably good and matching), measure peak to peak and period

4. BEMF  =  ( Peak to peak Voltage * Period ) / (SQRT(3)* 2) 

Can you post the waveform with cursors?

Thanks and Best Regards 

Venkatadri S 

Hi,

I tried to hand spin the motor and capture the waveform, please see below. Is the measurement / waveform correct?


As calculated from the probed value, the BEMF will be 0.07898. Can I directly plug this into the motor studio? Any conversion needed?

Thank you.

Tommy

Hi,

Thanks, seems using this constant with some tuning of startup can consistently startup the motor.

Tommy

Hi Tommy 

Thanks for confirming. 

Thanks and Best Regards 

Venkatadri S