WVC 1400 grid tie inverter Frankenstein version

[monkeyisland]

Welcome to the WVC 1400 Frankenstein inverter:

My WVC 1400 R3 failed after only two weeks of use, and using it at 50% capability ( only x2 solar panels instead of x4).
Two AC output MOSFETs failed. And also the main fuse, but that was my fault insisting with the circuit breaker.
I claimed AliExpress and they will send MOSFETs replacement which will take weeks to arrive.

Meanwhile I decided to buy MOSFETs myself, nowhere to find the original STB40N60M2 in D2PAK format at reasonable cost and low quantities. The chip shortage crisis seems to be also affecting semiconductors as many UK component sellers are giving 6 month delivery date and the prices are well higher up, at least compared with a few years back.

Pulling some information from YouTube and eevblog forums I found out that "similar" WVC inverters has been equipped with at least 3 different AC MOSFETs, the Vdss seems to be equal: 600-650v but "gate charge", "rated current" and "RDSon" are completely different between mine and them:
 RDSon 0.078ohn mine, 0.13 and 0.36 others.
 Gate charge: 57Nc 100Nc 27Nc
 Rated Current: 34A 25A 11A
... that made me think I could play up with specs finding the cheapest MOSFET available for experimentation. I bought the TOSHIBA TK25E60X in TO-220 package, pins bent and mounted on the air with direct fan cooling.

The main Fuse was not possible to be removed with hot air gun or with solder tip even when using fresh solder wire, hence the "double decker"fuse sorry looking.

The lid can not be closed but the is indoors, now mounted in a bigger control unit metal box with 2 cooling fans for the front and rear of the PCB board.

Has been working perfectly for two weeks, but final conclusion when I upgrade to 4 panels and perform the 1400w output rating.

[monkeyisland]

WVC inside metal case with double cooling fan

[jonpaul]

schematic? BOM? specs of switch FETs? line transients scope capture ?

j

[monkeyisland]

Schematic not available for the WVC 1400 R3.
It is a sub 150$ grid tie inverter, the repair is obviously a DIY more than  electronics repair shop so please understand that not worth to buy the oscilloscope to get the curves.


Original AC MOSFETs   STB40N60M2
Vdss 600v
RDSon   0.078
total gate charge   57Nc
RatedCurrent. 34A   
Max gate treshold Volt 4v

Replacement MOSFET chosen by me:
Toshiba TK25E60X
Vdss 600v
RDSon   0.125
total gate charge   40Nc
RatedCurrent. 25A   
Max gate treshold Volt 3.5v
In TO-220 package.

MOSFETs in the inverter  by YouTuber "How to guys"   
      
30NM60ND
Vdss 650v
RDSon   0.13
total gate charge   100Nc
RatedCurrent. 25A   
Max gate treshold Volt 5v

MOSFET by "All in the family'
member comment in the same YouTube linked above:

STD13NM60ND
Vdss 600v
RDSon   0.36
total gate charge   27Nc
RatedCurrent. 11A   
Max gate treshold Volt 4v