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7MBR25SA120-50 vs. 7MBR25SA120 Fuji IGBT modules

Discussion in 'Power Electronics' started by **Rafael**, Dec 10, 2018.

  1. **Rafael**

    **Rafael**

    15
    0
    Apr 27, 2015
    Hi there!

    I bought about a year and a half ago three Fuji 7MBR25S120 IGBT modules as spares to replace 7MBR25S120-50 modules if needed.

    I recently found one "-50" module bad in one drive and proceeded to replace it with one of the "new ones". However, I have found that whenever it heats up while in operation, it fails by exhibiting higher than 7 volts CE saturation voltage in one IGBT (not sure if it changes switch). I know this because gate drivers have a "desaturation" detection circuit which tells microcontroller about IGBT problems.

    The thing is that I was believing that module had initially acted up for my not tightening module down properly against heatsink. After not finding any other source of problem, I re-tightened module down and took unit back to work again (servo drive). This time unit worked fine for several hours until it "failed again." We let unit work for a couple of days longer at lower speed until it acted up again and then I removed it from operation. I thought that maybe module had been affected internally due to not tightening it well the first day and decided to remove it and replace module and tightening it down well from the beginning.

    However, something was bothering in the back of my head and decided to remove the lids of originally failed unit and the one I had just removed. My surprise was big when I found that devices are smaller in newer unit and even has a lower number of interconnecting conductors inside. See attached image.

    I have a couple of questions:

    1. Are these modules meant to be different due to the "-50" suffix in original module?

    2. I bought the replacement modules through AliExpress from a company in Hongkong that had units shipped from Singapore. Could these units be counterfeit? I asked the Chinese guy before placing the order and he said (of course) they were genuine.

    Thanks for your input

    Rafael
     

    Attached Files:

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,231
    1,861
    Nov 17, 2011
    Are you sure about the part numbers? I can't find 7MBR25S120 whereas 7MBR25SA120-50 is easy to find.
    There is also a 7MBR25VA120-50 rated for definitely less collector current than the SA type.

    The image suggest you have here two different modules, the lower one being rated for higher current judging by the chip size alone.
     
  3. **Rafael**

    **Rafael**

    15
    0
    Apr 27, 2015
    Hi Harald!

    Yes, you're right. It's a 7MBR25SA120-50. My mistake. The one at the top is 7MBR25SA120 without "-50". Supposedly, the -50 has to do with eco-friendly materials.

    I just finished a conversation with the guy in China I bought the non -50 units from and he insists his units are originals. The spec sheets I have found say that this module number is rated at a collector current of 25 Amps and CE voltage if 1,200 Volts.

    Sorry about the confusion. I tried to get units from Mouser electronics and Newark but it seems these modules are discontinued.

    Any idea where to get these units from?

    Thanks in advance.

    Rafael
     
  4. **Rafael**

    **Rafael**

    15
    0
    Apr 27, 2015
    Harald,

    See attached picture. I may not be seeing something that you may. It's 1:06 am here and I can barely see straight.

    Thanks for your input.

    Rafael
     

    Attached Files:

  5. Harald Kapp

    Harald Kapp Moderator Moderator

    9,231
    1,861
    Nov 17, 2011
    I cannot locate a datasheet specifically for 7MBR25SA120-50. All the datasheets i find are for 7MBR25SA120, even if advertised as 7MBR25SA120-50.
     
  6. **Rafael**

    **Rafael**

    15
    0
    Apr 27, 2015
    See attached file
     

    Attached Files:

  7. Harald Kapp

    Harald Kapp Moderator Moderator

    9,231
    1,861
    Nov 17, 2011
    That is for 7MBR25VA120-50, not SA. I've seen that one but dismissed it.
    If that is what you bought, then the fail can be explained by the difference in technical data:
    7MBR25VA120-50: IC continuous @ Tc = 80 °C -> 50A
    7MBR25SA120: IC continuous @ Tc = 80 ° C -> 25 A
     
  8. **Rafael**

    **Rafael**

    15
    0
    Apr 27, 2015
    Hi there!

    No, that's not what I got, at least not in the modules' labels. I guess I was half way asleep when I attached the 7MBR25VA120-50 file.

    The parts I got are:

    7MBR25SA120-50: the original I extracted from the drive, the one with bigger chips and more wires between chips and terminals.

    7MBR25SA120: the replacement from Hongkong. The part with smaller chips and fewer wires between chips and terminals.

    Thanks Harald, at least you showed that the part I got from Hongkong has a reason to exist. It could have been a "7MBR25VA120" part labeled as a "7MBR25SA120" part either intentionally or unintentionally.

    You also showed that one part is rated for higher current even though their part numbers are very similar.

    Thanks again, and have a great day!

    Rafael
     
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