What type of electrical motors are on the movie?

On the Youtube video they use commercial off-the-shelf consumer fans.

There is a control system - which is basically 4x OptoCoupler + Triac + (resistors and capacitors).

Those two motors on the movie are so nicely speed adjustable.

What they are, out of:

  1. single phase ac motors
    1. Split-phase motor
    2. Split-phase start capacitor motor
    3. Split-phase run capacitor motor
    4. Shaded-Pole motor
    5. Universal motor

for sure this is NOT no.5. (because they are specifically loud)

It seems that this is NOT no.2 neither. In the publication, author try to achieve the same, but withouth successful results (p.23-27), on page page.14 he states that this is 'Single Phase Induction Motor / Capacitor Start Type Motor / 370 W' https://es.slideshare.net/VISHNUG39/automated-speed-drive-using-raspberry-pi

Which of those motors form the list (no.1-no.5), ventilators on the youtube movies are then?

  • \$\begingroup\$ Take a screen shot and post it. \$\endgroup\$
    – Andy aka
    Commented Mar 18, 2020 at 10:24
  • \$\begingroup\$ Does it matter? And no, the control is terrible, you can see on scope that it skips entire semi-period, this is probably due to bad triggering circuit and/or program. \$\endgroup\$ Commented Mar 18, 2020 at 11:09
  • \$\begingroup\$ Not going to watch the video but the slides show very poorspeed control, about 10% speed variation for 2:1 voltage, and only document the unloaded condition. As expected for voltage control of an induction motor. \$\endgroup\$
    – user16324
    Commented Mar 18, 2020 at 11:21

2 Answers 2


The small fan is almost certainly a shaded pole motor - you can just see through the blades that the motor body is not round, and has cooling vents off to one side, due to the single coil construction.

enter image description here

These motors are exceedingly cheap, but don't have brushes to wear out like a universal(5) and deposit black dust on the blades, so are a good choice for low cost machines, despite their inefficiency.

Like all induction machines, they tend to run near the synchronous speed of the frequency of the supply to them, less an amount dependent on the load, known as slip. If you try to speed control an unloaded motor by varying the applied voltage, through amplitude or chopping, the speed variation will be minimal, but it takes only a small load to give a decent variation in speed, and these fans obviously do have that load.

The second fan looks like it'll have a cylindrical multipole motor, which could be either a permanent split capacitor (3) or a shaded pole.


It's almost certainly 5, a simple universal motor. I don't know why you ruled that out. They aren't "specifically loud".

For cost reasons, almost all household appliances with low requirements in compactness, power or reliability use them. "Fans" literally are the standard clipart example of things built with cheap universal motors.

The fact that it runs smoothly when "dimmed" can simply be attributed to the fact that it has a mechanical mass.

  • \$\begingroup\$ 99% of table top fans like that will have cheap little shaded pole motors on them. That makes them good for this kind of demonstration because you can control them via phase angle control, which is what they are doing there. \$\endgroup\$
    – JRaef
    Commented Mar 20, 2020 at 0:46

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