would capacitor banks surfice for 500w motor? also now looking in the old inverter there are 2 modules: switcher and spwm. spwm is egs002 which runs 23khz, too high for igbt, but has a 0-400hz variable function so i read. if i swap the crystal to a lower frequency and crank up the apparant frequency to 400hz to even out at 50 i might be able to utilise this module if its not kaput. the module has dead time setings too, but i dont know how adjusting the clock will affect these.

 

would capacitor banks surfice for 500w motor?

Of course it depends about capacity of the capacitor bank. I made a quick calculation and requirement is at least tens of mF (milli farads). I used 1500 W power and 500 ms duration. Capacitor voltage drop was from 350 V to 200 V (which is too much) and got 18 mF. Could be that my calculation is all wrong but it is possible to calculate/simulate the requirement.

 

How about using triac control? Basic triac control circuit has a potentiometer to adjust voltage. Triac controlled start would reduce starting current a lot. Basic triac phase control circuit made with diac and RC circuit might work even with PWM voltage if RC circuit filters the pwm voltage. I don't know if triac itself works with pwm. Perhaps it would be best to add LC filter to inverter output.

 

spwm is egs002 which runs 23khz, too high for igbt, but has a 0-400hz variable function so i read. if i swap the crystal to a lower frequency and crank up the apparant frequency to 400hz to even out at 50 i might be able to utilise this module if its not kaput. the module has dead time setings too, but i dont know how adjusting the clock will affect these.

SPWM is generated with eg8010 IC. It can also be used as a single phase motor speed controller. It would be best to use it with original crystal and use mosfet bridge instead of your big IGBT's. Perhaps mosfets could be salvaged from old ATX power supply. Operation mode has to be changed to V/F mode. From eg8010 datasheet ( http://voron.ua/files/pdf/micoshema/EG8010_datasheet_en.pdf ) page 7/20,

"In variable frequency and variable voltage mode (Pin VVVF at “1” high electrical level) 0～100Hz(FRQSEL1,FRQSEL0=10) or 0Hz～400Hz(FRQSEL1,FRQSEL0=11), pin FRQADJ needs to connect an external adjustable resistor. Pin FRQADJ sets output frequency and voltage. EG8010 maintains V/F as a constant. R23 sets output frequency at 50Hz when voltage effective value is 220V."

With V/F mode you can start the motor smoothly and adjust the speed -and therefore power taken from the solar panels- with a potentiometer as you wish.

If the big IGBT's are the only option then changing the crystal can be tried. Maximum deadtime of 1,5s can be too short for the 400A IGBT. Hopefully lower frequency crystal increases deadtime too.

 

Those IGBT blocks you have should easily be able to run at 23 KHz at the relatively light loads you will be running them at if they have the correct size of driver IC's on them.