MCT8316AEVM: Motor saturates at 70% speed

Suresh leley

Part Number: MCT8316AEVM
Other Parts Discussed in Thread: MCT8316A

I am using Smart Automation 80RBL90-24V, 24 Volts 8 pole, rated speed 3000, no load speed 4000 rpm BLDC Motor. I am running it at no load. I am using I2C to set % speed on the EVM. The speed as reported by FG at 50% is 25 Hz (25*60 = 1500 rpm) as expected. At 70% it is 33 Hz (1980 rpm) as opposed to expected 2100 rpm. From here until 100% speed remains constant. Any values I can change to get around this? Tried increasing CBC_ILIMIT to 1.0 V but had no effect.

SOA/SOB/SOC value as measured on pin 36 is 1.57 V. The CBC_ILIMIT is set to 4 A or 0.6V assuming 0.15V/A but dont get OCP or any faults, the motor keeps running. What is the scaling used to go from pin 36 value to actual phase current.

Tried to use Spin and Evaluate option on the GUI but the graph remained blank during Play, During Record it generated .cvs file with only col. A TIME in ms filled, nothing gets filled in channel 1 or channel 2..

Does the CLOSE Loop mentioned In the FG_SEL optioin refer to CLOSE SPEED loop or Commutation control? I had set it to 'output FG only in close loop' and set CLOSED_LOOP_MODE to Disabled but was still getting pulses on FG output.

Could you please provide some description for the DACOUT1/2 drop down options available in Basci Controls->Devicce and Pin Configuration-> DACOUT1/2 Variable saelect?

I have attached the regist dump regs.json file

over 1 year ago

0 Suresh leley over 1 year ago

Prodigy 150 points

0574.regs.zip

e2e site won't allow to upload regs.json, uploading it as a compressed zip file.

0 Joshua Horlander Cruz over 1 year ago in reply to Suresh leley

TI__Mastermind 24620 points

Hi Suresh,

I will need some time to look into this. I will aim to get back to you by December 15th at the latest.

Regards,

Joshua

0 Andrew Liu over 1 year ago in reply to Suresh leley

TI__Mastermind 18981 points

Hi Suresh,

Many of our team members are currently out of office for US holiday timeframe - but will be back in office by 1st week of January.

Please anticipate a delayed response & feel free to provide additional information in the meantime.
Best Regards,
Andrew

0 Suresh leley over 1 year ago

Prodigy 150 points

I ran some tests with another motor: Brother VGK C15-200N50L2AX 6 pole 2500 rpm motor and had no problems reaching the full speed.

0 Suresh leley over 1 year ago in reply to Suresh leley

Prodigy 150 points

I then collected plots for FG (channel 1, SOA channel 2) with the SmartAutomation 8 Pole 3000 rpm motor having problems reaching full speed. I have attached these plots. It seems the motor drops speed when ILIMIT is set to 0.2V this is seen in the plot:SmartAutoM100%_1-FG_2-SOA_ILIMIT_02.png.

Above ILIMIT = 0.4 this is not observed as seen in the plot captured at CBC_ILIMIT= 0.7V : SmartAutoM100%_1-FG_2-SOA_ILIMIT_07.png, but the maximum speed at 100% I2C setting is still limited to about 1930 rpm about 64%.

Changing INTED_ZC_METHOD from ZC based to Integration increases the speed to about 2131.5 rpm about 71%.

SmartAutoM100%_1-FG_2-SOA_ILIMIT_07.zip SmartAutoM_ILIMIT_07_regs.zip

0 Suresh leley over 1 year ago in reply to Suresh leley

Prodigy 150 points

I have attached the plot taken with INTEG_ZC_METHOD = Integration ILIMIT= 1.0V for SmartAutomation motor, the speed reaches 2114 rpm.

0 Akshay Rajeev Menon over 1 year ago in reply to Suresh leley

TI__Mastermind 23546 points

Hey Suresh,

Thanks for the update. We will aim to provide an update this week

Best,

Akshay

0 Suresh leley over 1 year ago in reply to Akshay Rajeev Menon

Prodigy 150 points

Do you have any updates? I need to finalize the board design soon, waiting on resolution of this issue.

0 Anthony Lodi over 1 year ago in reply to Suresh leley

TI__Mastermind 26726 points

Hi Suresh,

Today is a holiday for the US, but we will aim to get back to you later this week.

Regards,

Anthony Lodi

0 Joshua Horlander Cruz over 1 year ago in reply to Anthony Lodi

TI__Mastermind 24620 points

Hello Suresh,

Can you try setting the CLOSED_LOOP_MODE bitfield within the CONST_SPEED register to Disabled and testing if the motor can reach the targeted speed by slowing incrementing the speed command? In this mode the MCT8316A is not regulating the speed or power being delivered to the motor which gives the best indication if the MCT8316A can drive the motor at the target speed.

If you are able to reach the target motor speed with the CLOSED_LOOP_MODE set to Disabled, set this back to Speed_Loop and try adjusting the values of the SPD_POWER_KP and SP_POWER_KI bitfields. Tuning the Kp and Ki values is an iterative process, requiring trial and error testing to find the correct values.

Please try out these suggestions and let me know if you require further support!

Regards,

Joshua

0 Suresh leley over 1 year ago in reply to Joshua Horlander Cruz

Prodigy 150 points

I will try and let you know. I have one more questions regarding the documentation.:

1. On page 158- Table 9.3 of MCT8316A datasheet (SLLSFH8B – AUGUST 2021 – REVISED FEBRUARY 2022). PERIPH_CONFIG register is listed at address 0xaa. I couldn't find it mentioned anywhere else in the document. What are the bit definations for this register?

0 Joshua Horlander Cruz over 1 year ago in reply to Suresh leley

TI__Mastermind 24620 points

Hi Suresh,

The bits for the register PERIPH_CONFIG are all reserved offering no configuration. Thank you for pointing this out, we will look into making this more clear.

Regards,

Joshua

0 Suresh leley over 1 year ago

Prodigy 150 points

Hi Joshua,

I tried with the CLOSED_LOOP_MODE bitfield within the CONST_SPEED register to Disabled.

With CLOSE_LOOP3->INTEG_ZC_METHOD=ZC_BASED, I2C Speed command Percentage = 100%, speed is limited to 1965 rpm (32.76 Hz) on FG Out,

With CLOSE_LOOP3->INTEG_ZC_METHOD=INTEGRATION_BASED, I2C Speed command Percentage = 100% speed is limited to 2095 rpm (34.95 Hz) on FG Out,

The FG_DIV_FACTOR is set to 4 for the 8-pole motor. I have attached the register dump.

0 Suresh leley over 1 year ago in reply to Suresh leley

Prodigy 150 points

SmartAuto80RBL-90-INTEG_ZC_Methot-Integ012224.zip

0 Joshua Horlander Cruz over 1 year ago in reply to Suresh leley

TI__Mastermind 24620 points

Hi Suresh,

I will need some time to look into the register settings you sent, I will get back with you by Wednesday.

Regards,

Joshua

0 Suresh leley over 1 year ago in reply to Joshua Horlander Cruz

Prodigy 150 points

We are not using the 8 pole motor anymore, the other two motors I tried Brother, and Telco motion have no problem reaching full speed. We can close this issue. If you can please provide some information on how to use the Spin and Evaluate tabs on the GUI. So far when I tried it the graph remains blank.

Thanks for all your help.

0 Joshua Horlander Cruz over 1 year ago in reply to Suresh leley

TI__Mastermind 24620 points

Hello Suresh,

Using the Spin and Evaluation tab of the GUI requires that the EVM be connected to the GUI and that the GUI can read the register values from the MCT8316A. If the EVM is connected to the GUI and the GUI is able to communicate with the MCT8316A, then to display information the channels need to be assigned a variable and enabled, an example of this can be seen in the following image:

Once the desired channel configuration is set the play or record button needs to be clicked and the variable information should begin to be plotted on the graph. Clicking the record button will begin to store the plotted information into a .csv file which will be saved to your computer when the record button is clicked again to stop the recording.

Regards,

Joshua

0 Suresh leley over 1 year ago in reply to Joshua Horlander Cruz

Prodigy 150 points

I tried it but the graph and the .csv file remains blank. the red LED flashes at about 1 sec. interval. When I click on Auto read Motor Status or Auto Read All Registers or Auto Read Fault Status it flashes at higher speed, and the motor status, registers get updated, but the graph still remains blank. I used the POT on EVM to set different speeds, also tried I2C to change speed. It seems during Spin and Evaluate the GUI is not reading from the EVM but is doing so when Auto Read Status is clicked. I am using MCT8316A_GUI V 1.1.4 04Aug 2022 installed on Win10 PC.

graph_data.csv

0 Joshua Horlander Cruz over 1 year ago in reply to Suresh leley

TI__Mastermind 24620 points

Hello Suresh,

I will need some time to look further into this. I will get back with you by Tuesday of next week at the latest.

Regards,

Joshua

0 Joshua Horlander Cruz over 1 year ago in reply to Joshua Horlander Cruz

TI__Mastermind 24620 points

Hi Suresh,

After testing the Graphing feature on our end we confirmed that there is a bug with this feature causing it to not function as intended. We will work to fix this, thank you for bringing this to our attention.

Regards,

Joshua

0 Suresh leley over 1 year ago in reply to Joshua Horlander Cruz

Prodigy 150 points

Thanks Joshua, please let me know when you have a new version of MCT8316A_GUI with the fix. I will close this issue.

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MCT8316AEVM: Motor saturates at 70% speed