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Original question:

TMDSHVMTRPFCKIT: Short Circuit on Control Card Micro USB

TMDSHVMTRINSPIN: Short Circuit on Control Card TMDSCNCD28069MISO Isolated JTAG USB

Sooryanarayana Aithal
Prodigy 115 points
Part Number: TMDSHVMTRINSPIN
Other Parts Discussed in Thread: TMDSCNCD28069MISO, TMS320F28069

I am using the TI High Voltage Motor Control Kit, TMDSHVMTRINSPIN. Few months back I was able to use the board to turn a motor. After a gap of 4 months, today I tried to use the board again to turn the motor. I set up the system as I always have. I began by connecting the 15 V power supply, then I applied the 230V AC input. I then went to connect the micro USB cable to the f2806 control card (the USB end was already connected to the computer). Much to my surprise, this caused a short circuit/spark that fried my control card and my computer. The grounding jumper was in place on the board, M3-J5 is populated, J9 (main) not populated.  so I am not sure what caused this. I assume its either a ground loop or some kind of short inside the board. Is this an issue that has been experienced in the past? Any help is appreciated.

  • 0
    TI__Mastermind 27240 points

    Yes, the 15V power supply that you used may not be an isolated power supply and may have earth connection to GND (-ve output). Check it again.

  • 0 in reply to Ramesh Ramamoorthy
    Prodigy 115 points

    Hello,

    I have not used external 15V power supply at all.   SW1 on the main board is in position 2-3, and Vin for M6 is derived from output of M2.

    I suspect there is some design problem in GND isolation circuit in TMDSCNCD28059MISO card, 

  • 0 in reply to Sooryanarayana Aithal
    TI__Mastermind 27240 points

    If not the power supply, then it could have been through the scope EARTH pin. Check the continuity between scope probe GND and the mains cable EARTH.

  • 0 in reply to Ramesh Ramamoorthy
    Prodigy 115 points

    No Oscilloscope or any other external equipment is used.  

    TMDSCNCD28069MISO  control card is connected to computers USB port, using Isolated JTAG J1. and TMDSHVMTRINSPIN is powered ON.

    Few capacitors including C71, C68, C67 burnt.   Other damages not known.   Computer's motherboard and SMPS have gone bad. The cause of the problem to be ascertained before proceeding work on this. 

  • 0 in reply to Sooryanarayana Aithal
    Prodigy 115 points

    Is there any views from expert or any other user?

  • 0 in reply to Sooryanarayana Aithal
    TI__Mastermind 27240 points

    Looks like no body else has any suggestion.

    The issue you see here is usually due to the shorting of NEUTRAL and EARTH lines. If you have an isolation transformer, you may use it for the computer. 

    Like you mentioned, it was not a problem 4 months ago. The test setup, for sure, is not the same anymore between these two times. Let us know if you discovered the reasoning.

  • 0 in reply to Ramesh Ramamoorthy
    Prodigy 115 points

    For your kind information there was no change in test setup, and connection method between two time frame.

    As mentioned before, mother board and SMPS of two computers have gone bad due to this, apart from two control card TMDSCNCD28069MISO . 

    Even though we have procured a new control card, we do not have courage to connect to test setup since the solution is not given by Texas Instrument.

    Please refer two questions posted to this forum earlier by two other users.

    (1). TMDSHVMTRINSPIN: Does this Hardware is normal?

    (2). TMS320F28069: control card bur out, tmdshvmtrinspin

    In both cases, TI has acknowledged that there is design problem in control card TMDSCNCD28069MISO.     As I understand from those two posting, there is clear misunderstanding in isolation capacitor, it's value, etc.   Please clarify on that point.   Take internal help from TI.

  • 0 in reply to Sooryanarayana Aithal
    TI__Mastermind 41365 points

    Sooryanarayana,

    This capacitor is, as pointed out in the other threads, to ensure that the ground references do not float too far apart and allowing noise to be dissipated. This technique can be hazardous when working with certain high-frequency high-power noise.

    For the majority of our use cases it is recommended for this capacitor to be populated. As indicated in the posts removing this cap is a good idea for systems like yours.

    Regards,
    Cody

  • 0 in reply to Cody Watkins
    Prodigy 115 points

    Dear Sir,

    >For the majority of our use cases it is recommended for this capacitor to be populated. As indicated in the posts removing this cap is a good idea for >systems like yours.

    Thank you for reply.   However, above point is not very much clear.  We have connected the TMDSCNCD28069MISO to TMDSHVMTRINSPIN as mentioned in your document.  There is no additional or different connection.   How this type of system is different from "majority of our use cases" mentioned in above paragraph.

    As mentioned earlier, we are scared to continue the experiment with new TMDSCNCD28069MISO and New computer as it may spoil one more set of TMDSCNCD28069MISO  and PC.  If you STRONGLY suggest to remove the capacitor in TMDSCNCD28069MISO, we will make a try.

    Regards

    Sooryanarayana Aithal

  • 0 in reply to Sooryanarayana Aithal
    TI__Guru** 109730 points

    That means the controlCard is used with low voltage kits, not a high voltage kit as you. Recommend removing the C71 on the F28069 controlCard if the high voltage kit is connected to the AC power grid, not an isolated AC source. 

    And as mentioned above, you'd better use an isolated power supply for your computer and other measuring instruments like an oscilloscope. 

  • 0 in reply to Yanming Luo
    Prodigy 115 points

    > Recommend removing the C71 on the F28069 controlCard if the high voltage kit is connected to the AC power grid.

    Just curious to know are there any mention of above concept in any TI's published document related to TMDSHVMTRINSPIN or any other high voltage kit?

    (2). Is it okay if we use USB isolator similar to "Seeed Studio 114991949" ?  Will it serve the purpose?

  • 0 in reply to Sooryanarayana Aithal
    TI__Mastermind 27240 points

    If we have any other info, we would have given already. Like we said earlier few times already, you can solve the problem by using 

    1. isolation xformer for the computer (or)

    2. removing the iso cap on the control card 

    We have not any direct experience with any other isolation methods to suggest.