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TMDSCNCD28379D: Overcurrent Trip or VBus imbalance trips, high power application

CHRISTOPHER YECKEL
Prodigy 155 points
Part Number: TMDSCNCD28379D
Other Parts Discussed in Thread: SFRA, TIDM-1000

Good morning,

We are currently trying to scale up the TMDSCNXX chip to higher powers than the evaluation board. 40KW to be exact. 

We want to use the 3-phase power vienna correction as the front-end to our capacitor charging power supplies (very non-linear). 

Basing our design off the Eval Board, we scaled up components to their higher power equivalents. 

Currently, when we run build 4 the system corrects for a few seconds (with "ok" correcting) and then one of two things happen:

Overcurrent trip

Vbus imbalance trip. 

The VBus imbalance trip is accurate as the voltage across the caps does jump around and is not balanced. 

I am thinking the overcurrent trip is a symptom of improper current reading, despite the current out of the hall effect sensors (filtered) seems accurate. 

We attempted to use SFRA to correct for the Bus imbalance and can't get it to connect. 

We are running the EVAL board in parallel and that seems to work with the same signals (scaled to higher power of course). 

My questions are: What is the overcurrent trip indicating? Is it an overcurrent on the shunt resistors are out of the hall effect? 

Could this be leading to my Vbus imbalance trips? 

What is the procedure to connect and use SFRA? My technicians are unable to discern this from the literature, would SFRA even be helpful in this case? We cannot get SFRA to work even for the EVAl board. 

I know this is probably not enough information to really diagnose the issue so I will be checking back frequently to keep the discussion going. If this works this could be high quantity. 

Thanks! Note the water cooling and large inductors!

   

-Chris 

 

  • 0
    TI__Intellectual 1200 points

    Hi Chris,

    It looks like you are having multiple issues on designing your system. You can refer to the reference design in https://www.ti.com/tool/TIDM-1000

    Hope it is helpful.

    Thanks. 

  • 0 in reply to Qing Ye
    Prodigy 155 points

    Thanks Qing, I am well aware of the TIDM-1000 module as it is what we based our design off of. I am specifically asking what generates the overcurrent fault.

    -Chris 

  • 0 in reply to CHRISTOPHER YECKEL
    TI__Intellectual 1200 points

    Chris,

    If it is a real OC observed on the oscilloscope, you might want to check your power circuit operation to find the reason; If it is a mistrigger, you might want to check the signal on the adc conditioning circuit to see if any unexpected glitch; If it is doable, you can also keep emulator/debugger connected to your control board MCU and use expression window to check the adc value to see if it did exceed the protection threshold.

  • 0 in reply to Qing Ye
    Prodigy 155 points

    Qing, 

    We have set all the switches and jumpers on the MCU card as per the Reference Design.  But we cannot get the Software Frequency Response Analyzer(SFRA) to connect.  We can flash the MCU card and monitor the graphs from the A:J1 USB connection on the MCU card through the Code Composer Studio, but the SFRA does not see it. 

    Are we missing loading some driver necessary to make this connection?  Without having this tool, not sure we can get our product running.

    Also, can you specify whether it is the shunt resistors current signal or the signal from the hall effect probes that generate the overcurrent trip? 

    Thanks, 

    -Chris 

  • 0 in reply to CHRISTOPHER YECKEL
    TI__Intellectual 1200 points

    Chris,

    I am not clear about your questions "can you specify whether it is the shunt resistors current signal or the signal from the hall effect probes that generate the overcurrent trip? " Were you able to try the items in my last reply?

    Did you get any error message when you cannot connect SFRA? https://www.ti.com/lit/ug/tiducj0g/tiducj0g.pdf?ts=1659734024449 can you compare the files you are using with those in the ref design to see if any files or settings are not following?

    Thanks,

    Qing