On every electric fan I see, the power knob is always set up to have one position for “off”, one for “low” and one for “high” (and possibly “medium.”) But the order it’s in is always “Off-High-Medium-Low”. Intuitively it seems to me like it should be “Off-Low-Medium-High” If you ask me, they’re all doing it backwards. Does anyone else have any idea what I’m talking about? Why is it set up like this for every electric fan I’ve used? It’s cosmic questions like this that keep me up at night.
It’s usually best for an electric motor to start it in high speed. As I recall this is because the impedance is less at high speeds. Having the switch set like this encourages you to start the fan in high speed.
I think it’s not exactly that the motor should start in high speed, but rather that you want to apply more power to the motor to get it spinning, then back off. It would be fine to apply the higher power for so brief a time that the fan is still not running fast.
I think the problem with starting it on the low speed setting (of course you always start it at zero speed and it climbs infinitesimally from there) would be that it is liklier to not be able to start at all, because the bearings are old and full of sticky grease or whatever, and it would sit there cooking with all the electrical power turning to heat and no air moving around to keep the motor cool.
Bigger industrial motors may be started with higher power than they can continually run with, for the same reason.
Mine has simply 0 - 1 - 2 - 3, with 0 being off, 1 being low, etc. So it seems you’re just not buying the right fans.
My problem is 1 is too fast and noisy to let me get to sleep. I can’t imagine any circumstance that 2 or 3 could be of use. I need some sort of transformer to step it down by about 75%.
I had a feeling this question had been asked before. Not only is there a previous thread on it, the thread Crafter_Man linked to has a link to an even older thread. :o
Sounds to me like you’re the one who’s not buying the right fan… 
Having read most of the previous threads and this one I’m not all that satisfied with the answers.
I also have a fan that is the 0-1-2-3 type. 0 is off, 1 is low etc. I took the motor housing off and the motor is a single-phase capacitor induction motor. The field windings in this motor consist, in the simplest case, of a main winding on opposing poles on the stator (field) core and an auxiliary winding on poles that are physically at 90[sup]o[/sup] to the main poles. This winding is connected to the power through a capacitor which makes the current in this winding out of time phase with the main field current. The combination of the two fields produces a rotating magnetic field that generates a corresponding field in the rotor which then spins in synchronism (almost) with the main field. This type of motor has good starting torque virtually independent of speed and so will can have the switching arrangement above. That is it can start in low, medium or high speed with equal ease.
My fan has this type of motor and the speed of the fan is determined by the number of poles. Motor synchronous speed in rpm is line frequency in Hz*60 divided by the number of pairs of poles. So for 60 Hz and two poles the synchronous speed is 3600 rpm; for 4 poles 1800; for 6 poles 1200 etc. The actual operating speed is a little less than this because with these motors there has to be a little “slip” between synchronous speed and operating speed so as to generate an armature current to make the rotor turn. In many such motors the auxiliary field is disconnected by a centrifugal switch after starting because it is no longer needed.
Another type of induction motor that has good starting torque, although not as good as above, is the split phase motor. This motor has the same physical arrangement as the capacitor motor but the auxiliary winding is wound with fine wire so that it has a relatively high resistance compared with the main field winding. The resistance also introduces a time phase shift in the auxiliary field current and produces a rotating field. However not as much phase shift is provided, the rotating field varies quite a bit in amplitude during a cycle and the starting torque isn’t as high as with the capacitor motor.
Either of these motors could power a fan that will start easily at even low speeds.
The third type of induction motor is the shaded-pole motor which has low starting torque, but is the least expensive of the three and is suitable for fans because when the fan starts little air is being moved so there isn’t much of a load. This motor just has one winding. A short distance removed from the mair pole in the direction of desired rotation a small slot is cut into the field core. Around the core in this slot is place one or two shorted turns. These turns develop a current because of induction from the main field current and the current in the shorted turns develops a small magnetic field that is phased relative to the main field so as to produce a small rotating magnetic field component so the motor will start. However the starting torque is small and it could be that they should always be started in high speed.
My fan has OFF on both ends of the knob, so figure that one out.
I didn’t buy it … nice try though 