I notice that a lot of fans, including all I have recently bought, have3 speeds controlled by a switch. So I was wondering how they manage to control the speed (yeah, I know ... via the position of the switch :-) Latest one I bought has parts more visible (I don't want to take them apart). There are 4 wires to the switch. So it would seem likely that one wire is common and the other 3 are selected by position, and none are selected for off. There's a 3uf capacitor and what looks like a shaded-pole winding in the motor itself.
The motor type that seems to fit is "permanent split-capacitor", also known as "capacitor start and run".
If the starting winding is permanently connected, is there any design change over that of a switched winding that is needed because it will be permanently powered? For example would the number of winding turns need to be greater? Or maybe different capacitor? Or at at different angle in the stator?
I read that the switch selects taps in the main winding for speed. But is this just a selection that affects slip, or does it change the way the winding is slectrically configured? Could more taps allow more steps in motor speed? Is there a low end limit on the speed that can be set this way?
I have noticed that it always is the case that the first position next to the off position is the highest speed position. Is this done because that is the best for starting the fan from a not-running state?
I tested a couple of fans I have (the circulate air in the computer room by getting them spinning in the wrong direct by driving the backware with another face facing into it. Then I flip the switch and notice that the fan has no trouble getting started by quickly slowing down the rotation that's going in the wrong direction, to a stop, then going in the right direction. This works fine even which quickly switched to the slow speed.
My father has a ceiling fan with a pull chain that increments the speed in steps with 3 speeds possible, and also has a wall switch with 3 speeds. Turns out there there are more than just 3 speeds possible based on the combinations of both switches. How does this happen? I have not looked at the wiring, but I assume there are as many wires as the wall switch needs to have going between the fan and the wall switch. Could the pull chain switch be selecting different taps on the other end of the winding?
The ceiling fan has a reverse switch. I'm guessing that simply reverses the permanent start winding.