STEVAL-IPM15B short-circuit

[DGume]

I was using the STEVAL-IPM15B board to generate a single phase output between the U and V phases on a 24 ohms resistor load. Thus, I was also using only 2 pairs of IGBTs (A and B) out of the 3 available. Everything that was connected to the W phase (which I was not using) was left not connected.

I was commanding the IGBTs via sinusoidal PWM signals generated by a 32-bit microcontroller board. I did this by separating the result of the PWM algorithm into 2 separate outputs , 1 for each half period (positive/negative) of the sinusoidal reference signal. A separate line of code was written to always ensure that both outputs are not 1 at the same time, since I saw that the inverter didn't have an interlocking function. Then, each output was connected to the corresponding pins of the STEVAL-IPM15B board (output 1 with PWM-1H and PWM-2L and output 2 with the reverse). I also connected the GND and the 3.3V pins. Everything else I did not use.

For both the DC supply, as well as the Vcc supply, I used a PC adapter of 15 V and 3 A. I'm aware that the DC supply technically requires a minimum of 125 V in order to function properly, but for the purpose of my project, in which I only needed to generate the single-phase voltage on the resistor load, 15 V were enough.

At this point, everything was working properly and I was able to view the desired voltage between U and V using an oscilloscope. I also attached pictures with this result, as well as the setup.

Next, I wanted the resulting voltage to be able to synchronize with the frequency of the electrical grid. Using a 9 V instrument transformer connected to a normal power outlet, the micro-controller would read the analog values. Each time it would detect that the values would cross 0, from negative to positive, it would command that the sinusoidal signal used as reference to also be returned to 0 (using a variable which was 0 at the time), so that it may be in sync with the grid voltage. The algorithm still needed some work, but, nevertheless, my point is that the STEVAL-IPM15B board was still working fine at this point, still generating the desired single-phase output.

Then, the only change I made was that I changed the variable that controlled the sinusoidal signal to 90 degrees, so that now the output between U and V should be exactly the same, only 90 degrees out of phase with the grid voltage. As soon as I uploaded this change to the micro-controller board, while it still being connected to the STEVAL-IPM15B, as well as powered up from the 15 V supply, the STEVAL-IPM15B started smoking from somewhere near the inverter chip (couldn't see exactly where since it was underneath) and the chip burned, not working anymore. I unplugged it as soon as I could, but it was too late already.

It is clear that the board somehow short-circuited, but I cannot understand how. It was working properly with the last code before I changed that variable to 90 for somewhere between 2-3 hours. During this time, I checked regularly and the inverter chip wasn't getting hot almost at all, only the resistor load did. I also checked with the oscilloscope that the 2 PWM outputs would never overlap, so the interlocking protection that I wrote was also working properly. The power supply that I used had only 3 A and it also had short-circuit protection. The STEVAL-IPM15B board itself also has protection for something like this. I'm not ever sure that changing that 1 variable to 90 even had time to take effect, since the code has a written delay until the synchronization starts being verified, while the board started smoking immediately. So, I'm asking if there's something going on with how the board/inverter is working internally which I'm missing.

Thank you for your help!

[FSobe.1]

Something similar happened to me. I used 165v power supply, first the C9 exploded, it's rated to 400v, I have no idea why. Next the board was working fine when the shunt resistor exploded, I turned off all and checked the IGBT module, VCC was in shorted circuit with NU terminal. I also expected the IGBT module to protect for over current, but seems the protection is just be in short circuit and damage the IGBT module.

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