Hi All,

So I am trying to run a 650W ATX power supply with a 1000W inverter. It appears the power on surge is too much for the inverter. When I power on the ATX PSU, the overload light goes red and the inverter locks out. Can i put a suitable AC cap across the output of the inverter to rectify this?

Manual for the inverter is attached.

Thanks,

Joe

 

No. Connecting a capacitor across the AC supply will draw more current.
The input circuit of a switch mode power supply will be a bridge rectifier feeding a large capacitor . So a switch on the initial current will be much higher than the normal running current. This is probably what is causing the inverter to trip out.

Les.

 

is there any way to work around this or do u need a bigger inverter? What if connect PSU to mains, turn on the PSU using paper clip method, quickly remove from mains and put on to inverter. Idea here is the big filter cap in atx psu should still be charged up from mains.

 

A NTC thermistor current surge-protector would likely help (examples), which has an initial high resistance to limit the initial surge, but then goes to a steady-state lower resistance to minimize the voltage drop during normal operation.

 

awesome, I will try this, however I cant help but think that there would already be one installed from factory? Maybe not as this is not a typical application, and this supply is a consumer grade so may be left out for cost reasons?

 

that there would already be one installed from factory?

Doubt that.
Normally it's not a problem when operating from the mains, and manufacturers don't add cost to their products unless necessary, as you noted.

 

I've got this one handy, 3A tho.....

MF72-010D11 Cantherm | Circuit Protection | DigiKey

 

I've got this one handy, 3A tho.....

MF72-010D11 Cantherm | Circuit Protection | DigiKey

That means you shouldn't load the power supply with no more than about 300W of load (from 120Vac).
Is the power supply powering a computer (which probably would be less than that) or something else?

 

As the data on the inverter shows that it is manufactured in the USA I will assume it's output voltage is 110 volts. This means that the full load current will be about 6 amps. The thermister you suggest has aa resistance of 10 ohms at 25 Deg. C which would limit the current to about 11 amps. (This is 1100 watts for 110 volts.) This might just be OK but to be safe a resistance 12 at 25 C would be better. Also it is only rated at 3 amps and the power supply would draw a bit over 6 amps at full load. So you need one rated at a bit over 6 amps .

Les.

 

You may be able to reduce the start-up current by switching off all of the cooling fans until the computer is running. It is worth a try. Also any other add on items.