Inside a power inverter... Fuhjyyu's??

[Maxxarcade]

Here is an inverter I'm working on. The output MOSFET's are toast. I was surprised to find that a fairly high-end inverter is 100% F-you caps

[davmax]

Re: Inside a power inverter... Fuhjyyu's??

Wow 24 power devices, mostly MOSFET I guess. 8 empty pads?

What is the output power? Is it sine wave or modified square wave output?

The F caps seem to have considerable market penetration with manufacturers.

[Maxxarcade]

Re: Inside a power inverter... Fuhjyyu's??

the 8 empty spots are for the big output MOSFET's that I removed cause they were toast. It is a 2500W inverter. Kinda neat how it works. I think the occillator runs at 160Khz for the primary side. I believe it is modified sine wave output.

[japlytic]

Re: Inside a power inverter... Fuhjyyu's??

The waveform is modified sinewave output.
16 MOSFETs next to the transformers are used on the primary (battery) side, while the 8 MOSFETs next to the large inductors and 200V capacitors are used on the secondary (mains) side.
Depending on the model, some components are not fitted.
I found an inverter (with a similar topology to the pictures - high frequency switchmode transformer supply with MOSFETs at the high voltage DC supply to convert it to AC) which had no fuse protection on the LV winding on the secondary side - I had a close call when I accidentally shorted the rectifiers on it (The winding started to glow - fortunately, I disconnected it quickly enough!)
For 500W+ inverters, I only recommend using 24V units.

[Maxxarcade]

Re: Inside a power inverter... Fuhjyyu's??

Seems like there would be two occilators in this inverter then- One at 160Khz for the input side to give 2x 60v rails, and a 60Hz occilator to drive the output mosfets that give the current gain for the ac output. Quite a different setup than a conventional step-up transformer inverter with one occilator.

EDIT: err no, that would give it a square wave output, wouldn't it? It seems to have 4 phases on the input of each rail.

Wish I knew why it blew the outputs up, the owner did not overload it as far as I know. The output mosfets cost about $7 each, so they are looking at at least $50 worth of parts, assuming nothing else is bad. I'm concerned about the driver transistors (the TO-92 devices near the secondary side).

Looks almost like a car audio amp, with the way the case is designed...