How can single phase induction motor's direction be reversed?

Question

My house has a ceiling fan which has 2 wires which are connected to a capacitor, and Iam able to control the velocity and direction. After looking about these motors on the web I found out its probably a single phase induction motor.

So, this motor has 2 windings, one for driving the actual motor and the other for either starting the motor or keeping the motor spinning. I don't know which of these my 3-wire capacitor is doing. What I know is that the capacitor provides a phase change in the second winding so it can apply force when the motor is running.

So we have 2 wires to the motor, and they are in different phases, which makes the magnetic fields have different directions at different times. But: how can my fan spin the other direction as well?

Answer 1

Typically reversing the fan motor is done like this, an SPDT switch changes which end of run capacitor is connected to the feed, and in doing so changes which winding sees the advanced signal.

^{simulate this circuit – Schematic created using CircuitLab}

Answer 2

My concern with Andy aka's solution is that when the capacitor is moved from the aux winding to the main winding, the current in the aux winding may increase, and that increase may be beyond what the winding was designed for.

Here is an alternate way to swap the wires.

My schematic is modified from the same source as Andy aka's i.e. a paper uploaded by Thomas A. Lipo.

The unmodified schematic is here:

Answer 3

how can my fan spin the other direction

Well, I can't tell you precisely how they do it in your fan but consider this as a possibility: -

You swap the windings over. Use the capacitor on the regular winding and use the start winding with the AC supply and, it'll rotate in the opposite direction. Here's how it looks normally: -

Image from here and, if we swap stuff around it'll run in reverse: -