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What is the true impact of power supply differences - Japan, US, Australia?

I am used to British / European / Australia domestic mains where the nominal AC voltage is 240-Volts and the frequency is 50-Hz.

In Australia, the standard domestic outlet (General Purpose Outlet) is rated for 10-Amps, so can deliver up to 240 x 10 = 2,400 Watts of power by design. Many devices like electric heaters, hairdryers and kettles are rated at 2,400 Watts.

Most streets have three phases, and every third house connects to one of the phases.

In the US, the nominal voltage seems to be 120-Volts. At face value, this means you need 20-Amps for the same power and by inference you need twice the cross-section in the feed wires.

But that is only part of the story. The wires have resistance, and the voltage drop is directly related to the current flowing. To have the same proportional voltage drop at 120-volts as compared to 240-Volts, you would need to double the cross-section again, to four times.

Is this why there is so much discussion here about power cords, power conditioners and so on?

richardbrand

Showing 1 response by carlsbad2

carlsbad2's avatar
carlsbad2
2,023 posts
 

you’ve doubled the size of the wire twice unnecessarily. 240 volts has the advantage that current is halved so you need one size smaller wire to carry the same power.

I have a 240V amp and I use the same size power cord on it just because I can.

Power cords are sized for current flow. Power conditioners are to correct the distortion in the power signal (not the same as the distortion in the signal path). so 240 volts only gives you an advange when it comes to wire size.  240V will have no less distortion. of course we would keep going up in voltage to decrease wire size except it is a safety hazard. Frankly, 240V is much more dangerous than 120.

But in industrial applications small motors are 480V, large motors are 4KV, 6.9KV or 12KV. Transmission lines are 220KV or 500KV.

Jerry

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