It seems like fans are always off-high-medium-low. Is there a reason for this?
In: Engineering
One of my electrical engineering professors explained this to us.
The main reason is safety. A multi-speed fan is an electric motor with several windings. By using different windings, you get different torque and speed.
An electric motor winding is essentially an inductor, and inductors react in specific ways to changes in current and voltage. When you first apply a voltage to an inductor there’s a current surge, almost like it was a short circuit.
The high speed windings have the lowest such start-up current surge. They are put first so that the surge and associated heating of the wires is minimized.
I believe (but am not certain) that doing it this way is also a UL requirement.
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