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Cheap inverter issue - auto shutdown
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Posted: Monday, August 10, 2009 at 09:43 AM
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Note - the circuit into which I was plugging the inverter was actually not being shut off at the circuit breaker - so it was feeding the wiring in the whole house.

For my next experiment I tried an APC UPS (350VA).  It worked just fine when I plugged it into the home and it would power lights.  Based upon what the power meter was telling me (bouncing from 2W to 64W when I turn go from an aprox 40W draw to adding 20W of CFL lights)  these things are NON SINUSOIDAL!   The 350VA UPS was unable to startup my fridge as it couldn't supply the surge current for the motor.  I'd try one of the 1400VA UPS's I have - but they'd be a bitch to carry home on my bicycle.

Posted: Tuesday, August 4, 2009 at 07:50 AM
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I'm not sure if anyone has run into this - but it's puzzling me.

I took a 700W Motomaster and wired it, from my car,into my house to see if I could power the fridge and freezer.  Both were energy efficient models from 15 and 8 years ago.  The inverter can power them - when connected directly with an extension cord.

But if I connect the inverter to the house wiring - even though the circuit I'm on is SHUT OfF at the circuit breaker - the inverter just powers down with the fault light flashing slowly!  As the battery voltage is fine and there is no load (resistance is infinity) this screams that the issue is due to the length of the cable - a transmission line effect.  What' I'm lacking is a nice 50m (100m?) piece of cable to test this theory with!

For the curious the frige draws 100W when running, but was sucking 150W according to the UPM EM100 power meter when powered from the non-sinusoidal inverter.  To be honest, in the tests I've done I don't trust this power meter with the sort of waveform that comes out of these inverters!  This is based upon tests using the 700W inverter to power P4 computers - where the power meter indicated signif LESS power draw than the computer acutally uses.

Next up - I'm going to use a cheap UPS and wire it into my home to see if it'll power the fridge and freezer.  Why you ask?  Well - I expect more power outages and longer ones.  They were not unusual in the 1960's and 70's when I was growing up on a farm - and if I can use the juice in my car's battery to prevent losses of food in the fridge and freezer - for a cheap inverter - then I'm all for it.  I already use metal lined boxes in the garage for energy-free winter food storage (grains, nuts).

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