I have a PC consuming 400 watts hooked up to a 220 VAC automatic backup 1500VA 12V dc inverter since AC grid line is not 24/7 in my country.
The main problem is that sometimes when the AC power goes down the inverter successfully turns on and backup up power is provided to the PC with no problems. Other times the inverter makes a strange sound and the PC restarts.
Using a cheap DSO oscilloscope and an ACS712 module the problem seems to be high inrush current reaching 15 A during the switching time of the inverter which is around 12 milliseconds.
I have tried the following with no success:
1) A thermistor of 3.5 ohms for a certain time then shorting it with a relay. This did not limit the inrush current.
2) A 20-ohm high power resistor for a certain time then shorted it with a relay. This method limited the current but the PC restarted. Probably due to a voltage drop at this current level.
3) A solid state relay with zero crossing trigger to facilitate the slow rise of current. This minimized the inrush current but the problem remained.
Is there any other way to make this work?