Speed control for AC fan

[Bryan]

All:

Does anyone know what type of AC motors these types of fans use. I doubt a light dimmer would work to control the speed and one has to vary the frequency. Motor speed controller etc.

[amyk]

Likely some sort of induction motor - depending on power output, could be shaded pole (lowest power), split-phase, capacitor start, or permanent split capacitor, among others. Without changing the frequency, limited speed control is possible by varying the voltage. Otherwise it is as you say, a VFD will be necessary.

[Bryan]

There is a controller on the line cord but it only varies the fan speed by maybe 10%, I didn't want to crack the case to void the warranty, might do it anyway to see what it is doing, suspect just a pot and a cap.

[pbarton]

Same fan with a speed controller....
https://www.amazon.com/VIVOSUN-Inline-Ventilation-Variable-Controller/dp/B01CTM0JF2/ref=sr_1_17?_encoding=UTF8&c=ts&dchild=1&keywords=Household+Ventilation+Fans&qid=1608330416&s=hi&sr=1-17&ts_id=5446824011

Depends if the AC motor has one winding (two leads), or two winding's (3 or 4 leads).
There are several AC motor speed control circuits if you Google “ceiling fan speed controller”.

Strange, the Amazon listing fails to mention that its 110V and 60Hz.

[Bryan]

Exact same fan I have. Did a bit of disassembly. Controller uses a Triac (BT138), will try and draw the schematic out from the PCB. I think with different values, potentiometer... maybe one could lower the speed further.

[Ed.Kloonk]

Fine looking soldering job on the black wire there.

[Bryan]

Lol, true on that.  The one on the output side of the line is worse.

[NiHaoMike]

At that price, might as well just get a 120mm Delta server fan, print some adapters to mate it to a 6" duct, and build a simple 555 circuit to vary the speed. It would be way more efficient, similar or lower total cost after adding all the parts, and the speed control will actually work over a good range.