Senior Member
Joined: 11/12/2020
Location: CanadaPosts: 138
| Posted: 02:08am 08 Aug 2026 |
A tale of 2 mosfets
So, as mentioned earier, I have had an issue popping FETs. Over time, I determined that the problem occurred when the load presented to the inverter, went over 7.5kw. This includes any surge. 7.5kw seems like a lot, but items like my AC unit draws 12kw on startup.
It was time to order some replacements, and up to this point I had been using the Siliup SP012N02AGHTFA. I was using this part, mainly because the Huayi HY5012W had been on backorder, and the Voltage/Max Current/RDS(on) on the Siliup part was similar. I reviewed the data sheets again, and noticed that the SOA curves for the Siliup part looked weird. Although the part was rated at 310W, the DC curve showed the device could only withstand 10A at 10V Drain-Source which is 100w, not 310. Looking on the manufacturers website, the SP012N02AGHTFA has been replaced by the SP012N02AAGHTFA and the SOA curves look normal for this new device (at DC, the current x Voltage = device power rating. Anyway, after a bunch more searching, I found another device that had SOA curves like the Siliup part, the IR IRF100B201. At dc and 10v, the graph indicates the part will withstand 20amps or 200w total, while the device is rated at 440w.
Maybe I am missing something, but I ordered the HY5012W's. (note that the HY5608W will not work for me, as my battery voltage is 72V nominal)
While waiting for the parts, I looked at a huge number of SOA curves, and couldn't really find any devices that matched the Huayi parts. Here is a chart showing a comparison of some of the numbers derived from the published curves for each device.
After the parts arrived, I popped the top off one of them to compare.
Yes, the HY5012W actually has 2 FET dies in there. There are wires encapsulated in the plastic that connect each die to the outer pins.
Here is a comparison of surface area of the dies.
Looking at the specifications of other Huayi FETs, it looks like the 2 dies are from the HY3712B. That is one way to get a superior FET without designing a new part!
So now I understand why the wiseguy inverter was underperforming with the Siliup Fets. I still need to do some further testing, but for now I have raised the current limit.
Edited 2026-08-08 12:15 by oreo