150925-0955 EDT
Various comments, I have not read all the posts, but I consider some as being incorrect.
Probably not mentioned in this thread, but Ohm's law does not include the power equations, the power equations are Joule's law.
Ohm's law and its extension to include imedance applys anywhere that resistance or impedance is essentially constant over the range that voltage and or current varies. Thus, consider a forward biased diode. This has a non-linear V-I curve, but over some small range I can consider it as a constant resistance equal to the slope of the curve at that point.
An AC synchronous motor has an output speed that is constant, except for a phase shift, as motor load is changed up to the point where the load is sufficient to break sync.
An AC induction motor has an output speed that is synchronous speed (the speed of a synchronous motor) minus a slip speed that increases with load. The slip speed is very dependent on the rotor resistance. Higher rotor resistance and the slip is greater for a given load. Most induction motors are made with low resistance rotors. Fan motors are probably made with high resistance rotors.
Motor core saturation, when reached, this is gradual for most motors, may increase input current rapidly and thus motor heating.
Experiment on a rectangular box fan about 20" square on the fan face.
A variac (Powerstat) and a Kill-A-Watt EZ were used in the test.
Code:
V In Amp Watts VA PF
100 0.78 56.8 79 0.71
120 0.95 81.3 113 0.71
145 1.08 113 157 0.73
Motor speed varied a great amount, low at low voltage, and high at high voltage. Sensed by noise level. Note: speed will never exceed synchronous speed.
Since 240/120 V systems usually run high on voltage these days, mine is about 125 V, I woulf not put a 208 motor on a 240 V system. Life will be shorter, and in the case of a fan the noise will be greater if the fan has a high resistance rotor.
Many questions on this forum could be answered more quickly if the questioner did some simple experiements before asking the question.
Important criteria for most electrical products are:
Maximum ambient temperature.
Temperature rise vs input conditions.
Maximum internal temperature vs life.
Speed in the case of motors, intensity for lights, etc.
And others.
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