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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 erik_squires

erik_squires
16,554 posts
 

Most of the differences in how domestic voltages and Hz vary around the world are handled by the power supply, so this is rarely really an issue.

The voltages your equipment sees are due to the actual incoming voltage less any voltage sags in the line between your panel and the outlet.

If you want to know how much your voltage is sagging due to the draw between your wall and the panel, measure the neutral to Earth voltage with and without your gear on with a multimeter or something like this. Note your total voltage sag will be 2x the difference.

What most will discover however is that a great deal of the variation in voltages at your outlet are related to outside variations or major appliance usage such as AC’s and ranges.

The most cost effective way to ensure a constant voltage at your equipment is to use a conditioner with a built-in voltage regulator such as these from Furman.

 

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