Expedition refrigerator vs. cube/half size 120V?

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e9999 said:
I tried. Unfortunately, I used an inverter that could not handle the big starting surge. And it fried.
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was that an Autozone special 400 watter?
 
close. It was a Coleman Powermate 400W. IIRC, it did actually trip its breaker several times but I persisted to experiment a bit and see what would happen and it finally gave up the ghost. Keep in mind that the fridge only uses something like 125W when running so there was in theory a good deal of extra capacity but I pushed it too far. Had I been conservative it would probably have survived the first attempt or 2. I took it apart to see what had fried, I think there were at least some transistors that had literally blown up to pieces -I forgot- but I didn't bother fixing it, the cost of the parts was too high and it was too small for my purposes.
 
ac devices have a start-up spike draw...that 125 watts on start-up was likely close to 600...
 
the inverter was rated at 800W surge. And in fact, when I measured the startup surge it was about 800W or so.
 
LAMBCRUSHER said:
ac devices have a start-up spike draw...that 125 watts on start-up was likely close to 600...
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Not strictly accurate, inductive loads have a current spike at start up is a more accurate statement. Inductive loads include motors, such as the one in a fridge compressor.
 
rusty_tlc said:
Not strictly accurate, inductive loads have a current spike at start up is a more accurate statement. Inductive loads include motors, such as the one in a fridge compressor.
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yeah yeah yeah...
 
you say tomato, I say tomato :p
 
rusty_tlc said:
Not strictly accurate, inductive loads have a current spike at start up is a more accurate statement. Inductive loads include motors, such as the one in a fridge compressor.
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To be truly accurate pure inductive loads don't have a current spike as such, they have an exponential rise in current. But back to the fridge and what makes inverters smoke up. When an inductive load like a fridge motor is energized the initial high peak starting current observed is due to the low impedance the stalled motor presents to the supply and the absence of back emf - the voltage that is generated in the rotor that opposes the supply voltage and limits current. Back emf voltage opposes the supply voltage and the net effect is that instead of having say 120v across 10ohms impedance for 12 amps at some phase angle we would probably have something closer to 2, 3 maybe 5 volts across that same 10ohms impedance for a much much lower current.
 
PADDO said:
To be truly accurate pure inductive loads don't have a current spike as such, they have an exponential rise in current. But back to the fridge and what makes inverters smoke up. When an inductive load like a fridge motor is energized the initial high peak starting current observed is due to the low impedance the stalled motor presents to the supply and the absence of back emf - the voltage that is generated in the rotor that opposes the supply voltage and limits current. Back emf voltage opposes the supply voltage and the net effect is that instead of having say 120v across 10ohms impedance for 12 amps at some phase angle we would probably have something closer to 2, 3 maybe 5 volts across that same 10ohms impedance for a much much lower current.
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Very good explanation.
 
hey dude, remember me? I used to toss you in the trash can in the caffateria...you got a job for me?
 
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