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
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
