Power usage 120 volts versus 12 volts

[nothermark]

FWIW I'm just an old electronics technician who has had his fingers in many different aspects of the art and science. I learned early on that if I understood the basic physics then I could understand the system and that led to good break/fix or engineering results depending on who way paying me to do what at the time. The reason the utility grids use high voltage is that power loss is the current squared times the resistance. For a given amount of power there is less loss at high voltage than at high current in the same size wire. Power factor correction uses capacitors to compensate for the phase shift between the current peak and the voltage peak caused by inductive loads like big motors. FWIW it is conceivable but not normal to need to do the opposite. There are just a lot more motors than capacitive loads. ;-) From what I understand I the CG's already charge for peak loads. Having said that I suspect a lot of the issues around CG problems really stem from the local untility supplier. They do not want short term high usage loads that don't pay them for the capacity the rest of the year. If I had a seasonal operation I would be looking at some of the local generation options as a cost reduction effort. Not sure where the numbers would come out. Not sure I would bother looking too hard either as it is a pass through cost. ;-)

[Ray,IN]

Originally Posted by CountryFit

in theory, the power (v * i) consumed by an appliance on 120v should be equal to that when on battery factored by inverter efficiency. in reality, there are more than that; the current draw is much greater than what appears on paper.

the example i am giving below is my real life experience.

appliance: sharp carousel convection microwave. 1600w input, 800w output
inverter: magnum ms2812. efficiency 88 - 90%
battery working voltage: 13.0-13.4v

when the microwave is working, on paper i should expect current draw

1600 ÷ 13.2 ÷ 0.89 = 136a (approx.)

but i have observed it drew 154 - 158a. why was that?

one of the reasons the extra energy was used was the loss occured during current traveling. i am using #2 awg cables between battery and the inverter. while it was working, i touched the cables i could feel the warmness. the heat, another form of energy, was converted from electricity and lost to the air. this heat issue occurs on all electrical transmissions, even on the main lines at 10000+v from a power plant to the transformer stations. if i were to change the cables to #4 awg, heat will still be there but in a lesser degree.

hope this clears some of the clouds.

Isn't #4 smaller than #2 wire?

[Mr_D]

Originally Posted by MtnTrek

cool,
and what about power factor correction, and why does the utility grid infrastructure use such high voltages. Do you think CGs will ever start peak demand charges..... J/K

Happy motoring.

Throw in some phase angles for fun!

[CountryFit]

Originally Posted by Ray,IN

Isn't #4 smaller than #2 wire?

i corrected it in post #9. it should have been 2/0 and 4/0 respectively