I'm having hard time understanding how inverter works and why it works.

I mean why is it possible to power a say fridge (220V AC) with a 5v battery using a 5v to 220v inverter ?

And since this is possible why are electricity companies using high voltage lines ? that are so dangerous, why not use low voltage, and then increase it at the end point using inverter ?

Thanks to help comprehend it.

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    \$\begingroup\$ They use high voltage lines because lower voltages means higher currents, and higher currents means lower efficiency. This might give you some insight into how a step-up converter (because that's what you're actually asking about; the inverter is the bit that changes DC to AC) works; trading high current at low voltage for high voltage at low current. \$\endgroup\$ – Hearth Dec 14 '18 at 2:39
  • \$\begingroup\$ what if i have low voltage and low current ? \$\endgroup\$ – Xsmael Dec 14 '18 at 2:51
  • \$\begingroup\$ is it possible for example for a 3v battery with 1.5Amps to power a fridge ? \$\endgroup\$ – Xsmael Dec 14 '18 at 2:52
  • \$\begingroup\$ @Xsmael no, because that would be 4.5W, which is far less power than a typical fridge needs \$\endgroup\$ – BeB00 Dec 14 '18 at 2:58
  • \$\begingroup\$ No, it is not, because you have only 4.5 watts available to you there and I've certainly never seen a refrigerator that takes so little power. \$\endgroup\$ – Hearth Dec 14 '18 at 2:58

Power, i.e. watts, is ~ volts (V) * amperes (A). Powering a 600 watt fridge could be done with 240 V, 2.5 A, with 120 V, 5 A or with 5 V, 120 A. So there's no "magic", just a trade-off.

However, power loss as heat in electric wires is proportional to the current, measured in amperes. Though a 5 V battery could power the appliance, 120 A into the converter would require huge wires, about 50 times as thick as your house wiring. These bus bars would be very expensive, very heavy, hard to manipulate and difficult to connect.

In general, electric utilities and equipment manufacturers prefer to use the thinnest practical wire, so use higher voltages. Exceptions are in automotive applications, where 12 V batteries have a lower price (though many trucks use 24 V, now), and in shipboard use, where lowered voltage is considered safer in a wet environment.

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  • \$\begingroup\$ does thait mean that solar panels produce low voltage high current. which is then inverted to power appliances ? \$\endgroup\$ – Xsmael Dec 14 '18 at 3:10
  • \$\begingroup\$ oh, now i get the meaning of an inverter! :) \$\endgroup\$ – Xsmael Dec 14 '18 at 3:10
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    \$\begingroup\$ @Xsmael That's not the inversion that the name "inverter" refers to, though. That inversion is the polarity inversion involved in converting DC to AC. \$\endgroup\$ – Hearth Dec 14 '18 at 3:20

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