Yes, I know that C100 AC breaker is not a good idea for that invertors and I already said to the electrician all I think about he. It should be noted that I only deal with the repair of inverters and they got to me already in a faulty state. I already repaired a month ago the MPPT charger part of one of this inverters when the electrician connected about 7000Wt solar panels to one inverter...coulomb wrote: ↑Fri, 13 Jul 2018, 21:56 100 A is quite light for two inverters in parallel. It also sounds like they were only AC rated; you need DC rated fuses or breakers there. When they opened at something over their rated current, they may well have arced, pitting the contacts, and that may have interrupted the power to the inverters many times in a fraction of a second. The natural inductance of the battery cables may have caused voltage transients.
There are original 75V IRFB3307Z. It is interesting that their appearance is normal, but the leftmost and rightmost transistors are with burnt legs because of the high current. So, it's was a my guess that the voltage raised above 75V for a fraction of a second.
I think that it's not a reason. Invertors worked only 1 or 2 month, the capacitors usually do not dry so quickly. Full capacitance of 4 capacitors with unsoldered MOSFETs is 13300 (but I haven't ESR meter so I can not be sure).coulomb wrote: ↑Fri, 13 Jul 2018, 21:56 However, it's also possible that heat caused the capacitors that protect the battery-side MOSFETs to dry and become high impedance, allowing the transients on the 50 V bus to kill those MOSFETs, and the transformer coupled the transients (plus new ones from the short on the 50 V bus) to the DC-DC IGBTs.
Also, my inverters are bit different in some parts from described - capacitors are 3300uF 80V "success" (I guess that it is Chinese noname).
DC-DC and buck IGBTs are FGW50N60HD, inverter bridge IGBTs are FGW75N60HD.
Yes, of course. But users of this invertors said that they not exclude short circuit at the AC output. But I think that if it really was, it couldn't be a reason, it could cause increased load and tripping the battery breaker.
Of course, I will check and repair gate drivers.