Clarifying the Term "Nominal Voltage" - (July 6, 2023 Update) 

The short answer is "yes," every device has a range of voltage in which it can safely and effectively operate. Various codes and manufacturing standards may apply to any given device. I believe, for example, The National Electrical Manufacturers Association standards recommend that motors should be designed to operate satisfactorily at a voltage variation of plus or minus 10 percent. Other devices or equipment may be more tolerant or less tolerant of voltage variation. This is really a case-by-case matter.

Yes, loading a transformer makes a difference in voltage measurement values. On my 24V transformers, I often see 28V until I load them down. Interesting that you mention ghost voltage. I am planning on a video on the subject within the next few weeks. Thanks for the comment.

Actually wrong. The nominal is the specified voltage as per the specification. And that specification specifies tolerances above and below that nominal voltage. So in my country the nominal voltage is 230V but the actual measured voltage if the supply is 240 volts. And that 240 volts is NOT caused by a light load. The measured voltage, and when loaded, should be between Vmin and Vmax, where Vmin = Vnom - Vneg_tolerance Vmax = Vnom + Vpos_tolerance In my country the 240 is below VMax and greater than Vnom, so it it within tolerance and this is quite normal and quite acceptable. What you are talking about is two things: load regulation and cable resistance which causes voltage drop. The nominal voltage is not the open circuit voltage. That voltage does actually change across the country. And the point about "nominal" it is not the measured voltage. The dictionary definition of nominal is: "of a quantity or dimension) stated or expressed but not necessarily corresponding exactly to the real value." The key part of that definition is: not necessarily corresponding to the real value. Which is precisely consistent and is the case in my country where the nominal voltage is 230 and the measured voltage is 240V. So the nominal voltage is NOT the open circuit voltage. Definitely not.