• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 46 subscribers
  • Views 372 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BOOSTXL-3PHGANINV: Power ground (PGND) and signal ground (GND) disconnection

Lorrana Faria da Rocha
Prodigy 10 points
Part Number: BOOSTXL-3PHGANINV
Other Parts Discussed in Thread: LAUNCHXL-F28379D

Hello,

We are building a lab setup for testing and using the board BOOSTXL-3PhGaNInv as rectifiers in the setup illustrated below.

The system will be composed of three two-level three-phase converters operating as a rectifier connected in series. 

The system has a floating-point voltage on the DC link of each converter and we are gonna split the capacitor, so we have a mid-point in each converter, where the mid-point of the middle converter is grounded. However, according to the schematic of the BOOSTXL-3PHGANINV, the power ground and signal ground are connected. This poses an issue for us, because we don't want the signal ground which is connected to the microcontroller (LAUNCHXL-F28379D) to have a voltage potential. Due to the risk of possibly destroying the microcontroller and connected PC. 

Would it be possible to operate the system by disconnecting the signal ground from the power ground on the DC bus on the inverter board? We already removed the two resistances shown in the schematic below. The only way to open the net-tie would be to remove the copper trail from the board? Would there be any problems for the board if we do that? Is there anything else we can do to disconnect both grounds?

I appreciate the help in advance. Let me know if you have any questions.

P: I don't know if this qualifies in the right forum, let me know if you need to change the forum

  • +1
    TI__Mastermind 30910 points

    Hi,

    Unfortunately, the board cannot be operated by electrically isolating PGND and GND. The two grounds are two partitions of the same.

    Regards, Guang

  • 0 in reply to Guang Zhou
    Prodigy 10 points

    Hello Guang Zhou,

    It is a shame to hear that because this is crucial for our operation.

    But then an additional question. Imagine a system where we operate with two rectifiers as shown in the figure below:

    The first (top) converter will operate with the power ground (DC-) connected to the system ground, while the second converter will operate with the DC+ connected to the system ground as shown. The second converter will then have a floating potential on its power ground (DC-) and subsequently its signal ground. So the rectifier and microcontroller are floating on this potential (~12Vdc).

    The question: If we operate the two rectifier boards with two seperate (and isolated) microcontroller boards. Is it possible to operate the second (floating) rectifier board and microcontroller with this voltage potential on the signal ground? Given that we galvanically isolate the USB port on the microcontroller (LAUNCHXL-F28379D) from being grounded through the USB-cable. We will operate at low voltage (24Vdc) on the DC- side. 

    So in short: Can the LAUNCHXL-F28379D and BOOSTXL-3PHGANINV operate on a floating ground potential? And if they can what are the potential main issues we could encounter doing this. 

    Best regards, Lorrana.

  • +1 in reply to Lorrana Faria da Rocha
    TI__Mastermind 30910 points

    Hi Lorrana,

    The combo (launchpad + booster pack) should be able to operate on floating ground.

    The main concern is voltage compliance when interfacing with other peripherals without isolation. It appears you’ve considered these challenges and have come up with potential solutions. If you have USB disconnected when operating the system or if USB is isolated, I think it will be OK.

    Regards, Guang