controlling Two F28379D simultaneously

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ABDULRAHMAN ALHARBI 2024-8-22

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评论： Shivam Gothi 2024-8-28

Hi there,

In my project, I want to control two motors, one is the load motor and the other is MUT. I used two F28379D launchpads with two three-phase inverter. The first motor connected to the first inverter that controlled by first launchpad, and the other motor connected in the same way. The DC link, and axuiliuary supply are shared between them. The ground is connected between all of them. However, when I control the first motor (load), the ADCs for the other launchpad get lots of noises. I am not sure, whether, all these two launchpad should be supplied individualy or they have to communicate with each other. Could you please help in this matter.

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Swastik Sarkar 2024-8-28

Hi @ABDULRAHMAN ALHARBI,

Are you using a specific product, like Simulink, to conduct this experiment?

ABDULRAHMAN ALHARBI 2024-8-28

Hi @Swastik, Thank your for your feedback.

I am using CCS for this experiment.

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Answer 1

Shivam Gothi 2024-8-28

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编辑：Shivam Gothi 2024-8-28

Hello,

It seems that the issue is from the hardware side, and not from the programming side.

I cannot predict the exact cause of noise in the ADC measurements, because I do not have access to the hardware

However, I also faced the similiar issues when I was working on similiar hardware.

Here are few tips that can help mitigating the noise interference.

We can partition the hardware into two parts:

Control circuitry: It contains launchpads, gate drivers, sensors, analog filters and measurement cards. (All shares common ground, say GND1)
Power circuit: It contains DC link capacitors, three phase inverters and its connection with the motor.

Golden rule : The grounds of control circuit and power circuit should be isolated.
If you are measuring DC link voltage, the measurement circuit should have elecrical isolation from the DC link. (use opto-coupler based voltage measurement circuits).
Use shielded cable to transfer the analog signals from the sensor to the microcontroller. The outer shield of the cable should be connected to the ground of F28379D launch-pad. Generally, use of shielded cables mitigates noises due to electric fields.
Instead of directly connecting the inverter terminals to the motor, connect a common mode choke between them as shown in below figure.

NOTE: the common mode choke should be as near to the inverter as possible. The common mode choke offers high impedence to the common mode component of the current and thus reducing the interference due to "induction" effect. Refer to the below link to know more about common mode chokes:

https://sz-hotland.com/blogs/news/three-phase-common-mode-choke-a-comprehensive-guide-to-its-function-and-applications

(You can also surf the internet to find some content regarding its construction and working.)

Instead of directly passing the sensor analog signals to the ADC of launchpad, use an analog low pass filter (you can use sallenkey filter) to filter out the high frequency noise induced in the sensor cable. Refer to the below given link to know more about sallen-key filters.

https://en.wikipedia.org/wiki/Sallen%E2%80%93Key_topology

Try to keep the sensor cable away from the power cables of the motor.

Try to work around with the above stated approaches. It should solve the problem of electromagnetic interference.

Hope you find this usefull !

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ABDULRAHMAN ALHARBI 2024-8-28

Thank you.

Yes, there is RC filter mounted on each analong signal. I will double check the connection. Thank you again for your time.

Shivam Gothi 2024-8-28

Ok.

If the issue still persists, then please share the image of the hardware set-up. It will be useful for step by step debugging.

The challenging thing is to know the source of noise interference. Once the source is identified, appropriate measures can be taken to mitigate its effect.

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