help required anyone to removing fault in inverter

Dear one's.....
i have a three phase werkai electrical inverter china 3.7kw, problem is that when i checked the inverter initially i see the "IGBT" fp25r12kt3 has been blast and further i checked the circuit at the output of the "IGBT" some zener diode resistance and optocouplers are also faulted. then i removed three optocouplers a3120,diode by6, igbt and resistance after repairing all the circuits , first i checked on the series circuit and give the power but inverter fan and display is fail, voltage at the mosfet terminal gate and drain 533vdc but at gate and source terminal mv signal is noticed and not inverter properly working at the dc 24v terminal also mv signal...... please tell me how to remove this problem
model wks3.7kw
thanks

quite a complex question you are asking don't you have a good electrician near your place you should get the generator checked by him he can judge your problem much more efficiently