How does a Permanent capacitor motor actually work?

[NTesla]

TL;DR

I'm trying to understand how a Permanent capacitor motor, of the type single phase induction motor, that is used in ceiling fan, works.

Pic 1:

Pic 2:

Pic 3:

I'm trying to understand how motor of ceiling fan works. I have been scouring the internet since last 3 days. Watched a lot of youtube videos about it. Read quite a lot of websites related to single phase induction motors. Also read relevant chapters in 2 books about it. Till so far, I have come to the conclusion that the motor used in ceiling fan as shown in the picture is a single phase induction motor, and more specifically, the Permanent capacitor motor.

However, the youtube videos explain 3 phase induction motors, which i think has been explained quite good. Even in the videos which do explain single phase induction motor, the explanation is: the starter coil and the running coil create a rotating magnetic field. But how that rotating magnetic field is created(at intuitive level, or at math level) has not been explained at all. How the torque is created and transferred to the rotor, has not been explained at all.

I'm hoping that someone who has seen the pic that i have posted alongwith this post, and understands this type of motor would be able to guide me in understanding how this motor actually works, at the minutest level. If there is any book, resource etc, that in your opinion would help me in understanding this particular motor would be much helpful.

I'm an undergraduate student. I understand the impact on a closed conductor in a time variant magnetic field. I understand how electricity is induced in that closed coil. I also understand that a force acts on a current carrying conductor when placed in a magnetic field. What I'm failing to understand is that, in that particular motor, as shown in the pics,
how:
1) A rotating magnetic field is created. I'm talking about this particular motor only.
2) How the torque is created in a particular direction.
3) How that torque is transferred to the rotor of that particular motor.

 

[Tom.G]

From:
https://www.nidec.com/en/technology/motor/glossary/item/capacitor-run_motor/

"The capacitor-run motor is a representative example of the rotating-field single-phase AC induction motor. Its main application lies in fans. It has a two-phase winding configuration consisting of the main and auxiliary windings. A capacitance of about 3μF is connected to the auxiliary winding, as shown in the figure. Its function is to advance the phase of the current of the auxiliary winding by about 90° relative to the current of the main winding to create a rotating field."

Above found (after sorting thru much junk!) with:
http://www.google.com/search?q=how+does+a+capacitor+run+motor+work

Your photos seem to show that the rotor is permanent magnet type. Probably to keep the size down while supplying sufficient torque to drive the fan blades.

Cheers,
Tom

 

[NTesla]

Appreciate you help. However, the links that you posted above, in your reply, answers none of the 3 questions that I've posted above.

 

[Tom.G]

You may have noticed that your motor has two separate windings. These are positioned 'between' each other, i.e. looking around the periphery of the stator, the fields of the two windings alternate.

One of those winding is fed thru a series capacitor, whereas the other winding is connected directly to the incoming AC power,

If you have an electrical background you may remember that when driven by AC, a capacitor and an inductor (coil) affect a circuit in different ways.

When fed with AC, the current in a capacitor will occur near the Zero-crossing of the supply voltage, whereas the current in an inductor will lag after the peak supply voltage a bit .

Next, recall that it is the Current thru a coil that creates the magnetic field.

Putting all of that together, you have alternating coils in the stator with:

1) One set of coils is fed thru a capacitor, causing peak current and field strength near the Zero-crossing of the input voltage.​

2) Another set of coils is connected to the supply voltage, where the peak current is somewhat delayed after the Peak voltage.​

To the permanent magnets in the rotor, this is seen as a moving field and, being attracted to the strongest field, the rotor will chase the moving field all the way around the motor.

Hope this Helps!

Cheers,
Tom

 

[Baluncore]

What I'm failing to understand is that, in that particular motor, as shown in the pics, how:
1) A rotating magnetic field is created. I'm talking about this particular motor only.
2) How the torque is created in a particular direction.
3) How that torque is transferred to the rotor of that particular motor.

1. The rotating field comes from the sum of the sine current phasors via the capacitor phase shift, and the cosine current phasors from direct connection.
2. The direction of rotation is determined by the polarity of the sine coil connection, relative to the cosine coil. If you negate the sine coefficient, the rotation goes backwards.
3. The rotating field induces eddy currents in the external rotor, that drag the rotor in the direction of the rotating field. The rotor has a slower rotation than the rotating magnetic field, as it will slip, like any induction motor.

 

[Averagesupernova]

I don't understand why it is difficult to understand how a single phase capacitor motor creates a rotating magnetic field if you understand how a three phase machine creates a rotating magnetic field. Difficulty accepting that a capacitor causes a phase shift in the current?
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My trouble with understanding an induction motor in general was not realizing that the rotor acts as a shorted secondary winding of a transformer. The fact that the phase delays in windings due to a capacitor or any other possible means is not relevant.
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I don't understand why you don't understand.

 

[Tom.G]

I don't understand why you don't understand.

If the OP understood why he does not understand, he Would understand.

 

[nsaspook]

Part of the initial understanding issue is that the "single" phase motor is really a multi-phase motor at starting. The capacitor, the shade rings, etc ... are all methods to generate a second phase needed for a rotating magnetic field.

Capacitor-run motor induction motor

Capacitor-start induction motor
https://www.allaboutcircuits.com/textbook/alternating-current/chpt-13/single-phase-induction-motors/

Some "single" phase motors run better with dedicated second phase coil and other types just need that second phase coil to start spinning in the needed direction. However, if you move the single phase motor shaft with your hand (creating a "rotation vector"), it will rotate on its own without needing the second phase coil.
https://www.orientalmotor.com/ac-motors-gear-motors/technology/ac-motor-fundamentals.html