Hello ladies and gents. I want to share what I've been messing with recently.
Patient: Axpert VM III type 48V inverter with rated AC 5500W and 6000W PV input. 
All electrolytic capacitors in power circuits were replaced with brand-name ones 
(photo shows specific models Rubycon, KEMET, United Chemi-Con). 
I’ve added also active ventilation based on Sunon fans with magnetic bearings 
(MTBF 70k hours) + anti-dust caps. The ventilation mechanism is activated when
 the temperature on the main heat sink (IGBTs) rises above 35 * C 
(it turns on inaudibly at low speed, consuming 0.5W). If the temperature 
continues to increase, the fan speed gradually increases, it reaches its max
 at 50 ° C and higher (then the consumption from the DC 48V line is 3.5W). 
When the temperature drops below 35 * C the fans are turned off. 
What do You think?

Edited September 6, 20223 yr by Bocian

What do I think ? : absolutely spiffing , old chap . You've done some serious value adding adding here .

Those electrolytic caps was probably a few bucks ?

Well done !!!!!!

Wow, lots of fans! 

My only suggestions are replacing with long life 105°C capacitors (not just any name brand ones, a little more expensive), and consider replacing 80V rated MOSFETs with 100V rated ones. But the latter is a lot of work and expense, hard to obtain at present, and even clones may come with 80V rated MOSFETs these days. Original Voltronic inverters used to come with 75V rated MOSFETs, before the 64V battery voltage maximum.

But what you've done will probably extend the life of your inverter handily. 

It was one of the main parameters for which I was looking for brand-name replacements. Below ale declared lifespans:

• United Chemi-Con ELHS501VSN391MR60S 5000h@105C
• United Chemi-Con ELHS501VSN471MA50S 5000h@105C
• RUBYCON 450BXC47MEFC18X25 12000h@105C
• RUBYCON 63ZLH1800MEFC16x40 10000h@105C
• KEMET ALC80A123DF063 8000h@105C

Replacing transistors is pointless in my opinion. The benefits compared to the cost and time are not worth it.