Power factor of a dc machine

There are electrostatic motors. They can be a better choice than magnetic motors for some situations.

For example, check out this electrostatic motor that can be using in places with very strong magnetic fields like near MRI machines...

http://www.shinsei-motor.com/English/techno/

Electrostatic motors can also very efficiently directly use high voltage at very low current. The one described here can run forever off the voltage differential between two wires separated by a few dozen feet of height...

http://www.rexresearch.com/elstatix/esgenmot.htm#sciam

Here is a practical book with lots of electrostatic motor information, including many designs can build yourself...

https://www.amazon.com/Electrostatics-Exploring-Controlling-Electricity-Includes/dp/1885540043/ref=as_sl_pc_ss_til?tag=joshcom-20&linkCode=w01&linkId=GY4GGJ3S5CKUMRHM&creativeASIN=1885540043

Perhaps your difficulty is that the frame of reference or the "space" containing the magnetic flux and force vectors is rotating rather than fixed to points on the structure of the machine. In induction motors, the frame of reference rotates with respect to both the stator and the rotor, moving at the synchronous speed with respect to the stator and at the slip speed with respect to the rotor. In synchronous motors, the frame of reference is fixed with respect to the rotor, but rotates at the synchronous speed with respect to the stator. Thus the vector representations of the fluxes and forces have fixed positions with respect to the phase-vector representations of the AC voltages and currents.

I believe that this representation is developed by first examining the vectors with respect to the windings in the machine without considering the motion of the rotor and then examining the machine operating at a steady-state speed.

Equivalent Circuits

The analysis and control of electric machines makes use of equivalent electric circuits that are mathematically analogous to electromagnetic machines. They have a basis in physics, but that basis may not be as firm and direct as you might like. Engineers generally use the tools that will provide answers with a level of accuracy that is suitable for the ultimate purpose. Scientists strive to explain the laws of nature as thoroughly and accurately as humanly possible. Engineers strive to design products that are useful to human endeavors and economically affordable.

Terminology

Not all engineering terminology is carefully thought out. Even terminology that is carefully created is often simplified in everyday use. As a result, some terminology can have more than one meaning depending on context. I suspect that engineers are more tolerant of imprecise terminology than scientists may be.