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Original question:

TIDA-01513: Isolation Breach/Monitoring Question

TIDA-01513: TIDA-01513

REDDY Y
Intellectual 880 points
Part Number: TIDA-01513

Hi Rama,

we are working on EV-BUS battery pack which is 800V system . My vehicle OEM is asking me to disconnect the chassis connection i am using to monitor isolation. i have Connected 2M OHM resistor to Chassis from HV+ and HV-. i have 2 questions ??

1.Is it not suffiecient safe to have 2M-OHM resistor from Chassis to HV+ and Chassis to HV- ??

2. can you please suggest me how to measure Isolation resistance without connecting to chassis. all my internal electronics are running on Chassis ground again. if i disconnect chassis i will not be able to detect wire shorts i.e isolation breakdown

3. whats standard telling about the HV+, HV- connection to chassis?? as per standard are we allowed to connect to chassis with High res in series ?? 

further communications we can have privately , as the info here is confidential for me to share

  • 0
    TI__Expert 5130 points

    Rami, hello and thank you for your interest in Texas Instruments.  Your inquiry has been forwarded to our Automotive Systems team in Germany.  Please allow us 1-2 business days to respond due to the weekend and Monday's Texas Instruments Labor Day holiday. 

    Best Regards,

    John Fullilove

  • 0
    TI__Prodigy 440 points

    Hello Rami Reddy,

    1.Is it not suffiecient safe to have 2M-OHM resistor from Chassis to HV+ and Chassis to HV- ??

    -  It depends on OEM requirements and your architecture to measure the Isolation parameters. We cannot say straight forward to comment on the same.

    2. can you please suggest me how to measure Isolation resistance without connecting to chassis. all my internal electronics are running on Chassis ground again. if i disconnect chassis i will not be able to detect wire shorts i.e isolation breakdown

    - If you disconnect chassis and if you read a leakage current that is failure due to external breakage of Isolation path from High Voltage to Chassis Ground. Based on the Isolation measurement algorithm, disconnection of switch needs to be performed.

    3. whats standard telling about the HV+, HV- connection to chassis?? as per standard are we allowed to connect to chassis with High res in series ?? 

    - Let me know the market and standard which you are referring here. Most of the standard does not specify architecture, it only gives the parameters to be met with given test/boundary conditions. As per it is your design to architect the components(Resistors with switch or without switch). As per me Resistor with switch gives more freedom for accuracy, but end of the day it depends on your requirements and architecture.

    Hope this clarify's your queries...

    Thanks

    Regards

    Rama

  • 0 in reply to Rama Chandra Reddy Kambham
    Intellectual 880 points

    I am designing EV-BUS BATTERY PACK 650V to meet  ISO26262 ASIL-D Standard 

  • 0 in reply to REDDY Y
    TI__Prodigy 440 points

    Hello Rami Reddy,

    ISO26262 is automotive development process framework where as ASIL D is the safety goal for a particular functions/parameters.

    Do you have any reference/standard asked by OEM for Isolation Measurements? To be precise, circuit shown in TIDA-01513 can be used to measure the isolation parameters. Circuit can be modified and output parameters can be used to comply with requirements given by OEM.

    Thanks

    Regards

    Rama

  • 0 in reply to Rama Chandra Reddy Kambham
    Intellectual 880 points

    Hello Rama,

    Vehicle OEM is using their own brought out Module ( Supplied By Bender) for Isolation measurements which is installed in the vehicle but outside the battery pack. We are battery pack suppliers to Vehicle OEMs. As i have many Wires running inside the battery pack in between Different ECUs i want to detect the Wire faults also. thats the reason i am planning to have dedicated Isolation monitoring system inside the battery pack to detect the faults for safety reasons. 

    Thanks

    Rami Reddy

  • 0 in reply to REDDY Y
    TI__Prodigy 440 points

    Hello Rami Reddy,

    TIDA-01513 can be used to measure the isolation parameters for the battery pack. High Pot resistors can be used to detect the same. Switches can be used based on the accuracy needed and algorithm. Refer the user guide for more information.

    Thanks

    Regards

    Rama