They are series connected motors, so the armature current also runs through the field.

Yes, this is one type of motor that I'm quite familiar with. When I was a kid, I wondered how come those motors didn't reverse their direction when I rotated their plug 180° and reconnected it.... and then it downed on me, how come they can work on AC at all? ... so I drew a nice diagram on a piece of paper, and stared at it for a while until I finally "saw it" turning in my head... years after that I learned Tesla's history and his invention of the first AC induction motor, and became amazed and astonished at his genius.

 

I may have posted this before, but some decades ago a washing M/C manuf. used a Universal motor to operate it, for this, Motorola came up with specific IC geared to this, the TDA1085a.
This was a Triac based controller using a low resolution opto pick up wheel for speed monitoring and control.
The machines usually have a bridge after the Triac and a series inductor/choke.
The motor and controller came on the surplus market for a while after falling in popularity, I used them in controlling some home based power tools, particularly nice on a band saw.
Max.

 

I put a high voltage few uF film capacitor in series with a 240VAC little fan and it made a series resonant circuit which boosted the 120VAC voltage to the fan. But for a heavy duty drill you would need a truckload of paralleled capacitors.

 

I put a high voltage few uF film capacitor in series with a 240VAC little fan and it made a series resonant circuit which boosted the 120VAC voltage to the fan. But for a heavy duty drill you would need a truckload of paralleled capacitors.

I assume you are referring to a AC induction motor?

@cmartinez version is a Universal motor.
Max.

 

I assume you are referring to a AC induction motor?

@cmartinez version is a Universal motor.
Max.

Yes, a little AC fan did not have brushes.