(The same concern can use to areas with 220/240V mains, if ns am no mistaken.)

Frequently ns see combined ratings indicating that something is perfect for 110, 115, 118 or 120V (in the US). I"ve constantly referred to mains strength as 120V yet with the understanding that it varies due to the fact that of:

Different method of generation (number the phases, etc.)Line losses and also imperfect conditions

When making something, need to one always test using the lowest intended voltage (110)? What reasons are there for the differences in mains voltage?


In the US, the electrical utilities are supposed to provide power come residential customers at anywhere between 110 and 125 VAC RMS. The value 117 (or 117.5 or 118) is often seen on products, due to the fact that that is the middle of the stated range.

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If you"re arising a product for general sale, it would certainly be way to add a experimentation margin that"s at the very least 5% or also 10% beyond the nominal range — perhaps 100 to 140 VAC RMS.


Adding to the answers here regarding why the power agency does play through the voltage: lock will perform their ideal to keep your countries" welcomed hertz value, generally at 50 or 60 cycles. They will sacrifice (brownout) voltage come insure the most important variable because that equipment, hertz. Any change will make motors spin much faster or slower, meaning timers and also the choose will not role properly. A voltage drop might be native "imperfect conditions" however hertz sports is for sure unacceptable.


Addressing simply the factor why voltage varies, you are correct in thinking line losses beat a role. No common wire is a perfect conductor. Superconductors come very close, but for those of us working with normal electrical components, wires space just little valued resistors. Together such, they endure a voltage drop when present flows v them, through Ohm"s law. This is likewise why long-distance strength transmission is done at high voltage, and also stepped down as close to to the customer together pratical.

You can observe this straight when a engine in your fridge, wait conditioner, or clothes dryer turns on: the high beginning current the the motor pulls the voltage in your house down, dimming any kind of incandescent lights. Of course the running existing is lot less, so the lights appear to go back to their original brightness, however if you to be to measure closely you would discover they space a tad dimmer than they space without the engine running. With a huge AC compressor also the existing after starting is significant enough come dim the lights till it switches off.

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Of food the electrical utility attempts to mitigate this effect, however nothing is perfect.