Inverter and 240v mini fridge?

[swampthing]

Can any electrical gurus answer my conundrum please? I have a brand new 240v mini fridge (compressor type) The spec badge on it states 47watts input. I have a 150w inverter (new) but it wont start the fridge. I borrowed mates 600w and that works fridge. What is the smallest inverter that will work and why wont 150 w run a 47w fridge. Please help, cant face any more warm cider. /forums/images/graemlins/confused.gif

 

[ccscott49]

The smaller inverter will run the fridge, just wont start it! I dont know what the startup current is for a small fridge, but I would bet its about 300 watts minimum.

Anybody you know got a 300w inverter you can try? By the way, pure sine wave will be much better for the fridge compressor.

 

[swampthing]

Thanks for speedy reply, Am I correct in assuming that a larger inverter has greater losses than a small one? Also ,are the pure sine ones dearer, ?

 

[ccscott49]

Large inverters are normally same as small ones reference losses. Pure sine wave are more expensive, but IMHO worth it, in the long run, your fridge would last longer., but if you arent bothered about longevity, go for modified sine wave.

 

[jeremyshaw]

Inductive load problem, surely, as Englander says. See
http://en.wikipedia.org/wiki/Inrush_current

My AC watermaker runs at 15amps, but needs over 25amps to kick off. You might be able to re-borrow your friends big inverter and see what the peak load draw is with a decent clampmeter - or ask the manufacturer.

Any electricians know if there is a rule of thumb for electric motors' inductive loads vs normal loads? I've never been able to find one...

 

[charles_reed]

Ironically all the 12v fridge units on the market use a 230v AC compressor. The clever part is they have a dedicated solid-state transformer to convert the DC to AC.

Mine pulls 6amp @12v on start up sinking back to 3 amps if system voltage is less than 13.5v or staying @ 4 amps when on "supercool" when system volts exceed 13.5.

From those figures I'd doubt the effectiveness of your 150 watt inverter. I had a Belkin 150 watt inverter which, if faced with anything like its rated output, just squealed and died.