• TI Thinks Resolved

SN6501-Q1: Selecting a transformer

Intellectual 2750 points

Replies: 5

Views: 64

Part Number: SN6501-Q1

Hi,

I want to use SN6501-Q1 for an automotive application. Primary side is low voltage system where people can touch in some cases. The secondary side will have common GND with a 460V battery pack. So I will need a suitable transformer for safety.

As far as I know, the transformer will need to meet certain values for creepage and pri-sec clearance. In addition, it will need to pass hipot test under certain voltage (let's call it A) in 60 seconds.

In order to select the lowest cost Wurth transformer, what is the recommended voltage for A in this case?

Regards,

Kien

  • Hi Kien,

    Thank you for posting to E2E! Recommended isolation voltage levels depend on system specifications, expectations, and whether any standards need to be met by the isolation system and/or end equipment.

    If the full 460V of the battery pack is the highest expected voltage present in the system -- including transients, surges, discharges, etc. -- for a maximum of 60 seconds across the separate GND potentials, then a transformer providing this exact level of isolation might be enough for the application.

    That being said, if humans interface with either side of the isolation barrier, reinforced isolation ratings (which include margin over "basic" and "functional" isolation ratings for the same voltage level) are recommended. Are you aware of any specifications, expectations, or standards for this project that should be considered?

    We cannot comment on prices for transformers since vendors provide these components separately from TI.


    Respectfully,
    Manuel Chavez

  • In reply to Manuel Chavez:

    Manuel,

    Thanks for your reply.

    The requirements include:

    -        Standard: IEC 60664

    -        Isolation ratings: reinforced

    -        Maxium voltage of battery pack: 4.2V*110 cell=462VDC. There are no transients, surges.

    There are many transformers which TI recommend in the SN6501-Q1 datasheet. There is a parameter called Isolation (rms) which is test in 60s. For example, in the picture below, transformer 760390014 has isolation of 2500V rms in 60s. So with my application, what voltage is enough ? Can you give me the formula to calculation this voltage?

     

    Regards,

    Kien

  • In reply to Kien:

    Hi Kien,

    Thank you for sharing these additional requirements. Necessary isolation voltage levels are typically determined by functionality of an end application or requirements to meet safety standards.

    The 60s isolation voltage specified in component datasheets quantify the device's isolation performance under short-term overvoltage conditions -- transients <60s long. Working isolation ratings define an isolation device's capability to provide isolation at certain voltages for the device's lifetime. These two parameters are not necessarily related and should not be extrapolated from each other.

    If our customer requires >462VDC isolation for the application's entire expected lifetime, then this rating should be the focus instead of the 60s rating. The Würth transformer shared above is not specified to meet >462VDC isolation working voltages, but perhaps a transformer from the PM2185.0xxNL family will suffice for our customer.

    Looking into IEC 60664-1, Table F.4 shows minimum parameters for 500Vrms working isolation voltage qualification to meet this standard. The parameters vary based on the isolation device's material group (specified in datasheet), the end application's expected pollution degree, and whether the ratings will be achieved for basic or reinforced isolation. Does our customer want to meet 500Vrms basic or reinforced isolation per IEC 60664-1 for this project?


    Please share our customer's thoughts on the above.


    Thank you!
    Manuel Chavez

  • In reply to Manuel Chavez:

    Hi Kien,

    Please let us know our customer's response to the previous post and if there are any questions. If there is no response soon, this thread will be closed due to inactivity.


    Thank you,
    Manuel Chavez

  • In reply to Manuel Chavez:

    Manuel,

    Thanks for your supports.

    Customer doesn't have any further question for now.

    Regards,

    Kien