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ISO7821: 1500v solar inverter system

Howard Zou
Genius 12365 points
Part Number: ISO7821

Hi,

my customer choose ISO7821DWWR in their system to achieve isolated UART communication between C2000 and STM32F107.

C2000 is controlling a 1500VDC solar inverter system.

And they need to achieve reinforced isolation between C2000 board(hot side) and STM32F107 board(cold side).

And they said that 15mm clearance and creepage is a must for them to pass the reinforced isolation certification for 1500V system.

And in the datasheet 8.3.1.1, TUV column: I don't know whether I should choose 1000VRMS or 1450VRMS.

5700 VRMS Reinforced insulation per EN 61010-1:2010 (3rd Ed) up to working voltage of 600 VRMS (DW package) and 1000 VRMS (DWW package)

5700 VRMS Reinforced insulation per EN 60950-1:2006/A11:2009/ A1:2010/A12:2011/A2:2013 up to working voltage of 800 VRMS (DW package) and 1450 VRMS (DWW package)

And if 1450VRMS, does it correspond to 1450*1.414=2050VDC?

  • 0
    TI__Mastermind 49475 points

    Hi Howard,

    I understand that you had inquired about the same topic in another E2E post (link below) in the past.

    We currently do not have a device that supports 15mm clearance / creepage. I understand this is the requirement for customer end equipment but the weakest point in their product would be the PCB which I believe would need much more creepage than 15mm. Some of the options that customer can choose to achieve higher creepage using ISO7821 is to use potting or other coating methods if possible.

    I am copying below links to two other E2E posts on similar topic so that you have more details.

    TUV is only the certification agency and it certifies products for various standards, the two ratings from two different EN standards are different probably because of the difference in the test approach they follow and the definition they have for working voltage. Please allow me to check with my colleagues on this question and come back to you by Wednesday (9 Sep) on this. Thanks.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    TI__Genius 12365 points

    Rao,

    thanks.

    The customer says that the TUV people says 15mm is a must for 1500V system for reinforced isolation certification, and their PCB material is already group I.

    I would like to know if it's true.

    Since we have 2 different level certified with TUV. If 1450RMS can fit into this case, we should be able to argue that our device is okay.

  • 0 in reply to Howard Zou
    TI__Mastermind 49475 points

    Hi Howard,

    Thank you for sharing additional information.
    Please note that the standard referred for TUV certification in ISO7821 datasheet is different from the customer end equipment standard. The solar inverter equipment standard IEC 62109-1 may have the 15mm creepage requirement at the end equipment level and ISO7821 is not certified for this standard.

    Hence, it is possible that TUV may consider ISO7821 to be not meeting their 15mm creepage requirement because of the 14.5mm creepage supported by the device. Thanks.

    Regards,
    Koteshwar Rao

  • 0
    TI__Mastermind 49475 points

    Hi Howard,

    Sorry that ISO7821DWW currently doesn't meet your customer requirement.

    The DWW package was chosen among the possible package options at the time of ISO7821 development and it was done to support higher working voltage requirements by all the applications that may require such high voltage. Please also know that the device ISO7821 is not limited to be used for any specific few applications, it being a general purpose higher performance isolator, can be used in all applications requiring creepage upto 14.5mm with working voltages of upto 2kVrms.

    Let me know if you have any other questions, thanks.

    Regards,
    Koteshwar Rao

  • 0
    TI__Mastermind 49475 points

    Hi,

    The discussion has moved to email, hence, closing this post. Thanks.

    Regards,
    Koteshwar Rao