Differential-pitch pole-armature winding is the core technical mechanism claimed in US Patent 2,021,177 (d'Angelo, 1935). It is a method of winding the primary and secondary circuits of a pole-armature machine in which the secondary winding has a longer pitch than the primary, and at least some secondary turns encircle two, three or four poles rather than a single pole.
The mechanism as stated
In the patent's primary example (Figs. I–V), the stator has eight long narrow poles and the rotor four poles. The primary circuit consists of coils each surrounding a single pole, with adjacent coil ends sharing commutator segments and all coils on a pole interconnected in series. The secondary winding has a much greater pitch: each turn encircles a pair of poles, and the winding is wound twice around a pair of poles. For two-phase output, two separate secondary windings are placed one pole apart.
Because each secondary turn encircles two poles, and the pair's polarity is reversed twice per half-cycle (once for each pole), "one coil of the secondary winding is subjected to four variations of the magnetic flux in one half cycle." The patent states the EMF caused by the changing signs of the stator poles "is induced four times in each coil of the secondary circuit during one complete revolution of the rotor."
Why the patent says the secondary EMF exceeds the primary's
The patent gives three reasons:
- Additive EMFs. The rotor's revolving field induces one EMF in the secondary; the stator's revolving field (from pole-sign reversal) induces another. "The total electromotive force induced in the secondary circuit is thus created firstly by the changing of the signs of the poles of the stationary armature, and secondly, by the revolving magnetic field of the poles of the rotor."
- Four flux variations per half-cycle in each secondary coil, as above.
- Short primary pitch forces higher rotor speed. "In order to enable the primary winding to develop its normal counter-electromotive force, the rotor will make more revolution than would have to be made if a full-pitch winding were used, provided that the machine runs on direct current. A quickly rotating rotor will cut more lines of force and this will contribute to the increase of the voltage in the secondary winding." On AC, the field must instead be strengthened to develop normal counter-EMF.
The patent concludes that the secondary EMF is greater than the primary's "although the secondary circuit has a smaller number of conductors and turns."
Variants
- High-voltage DC secondary (Fig. VII). Each winding around a pair of poles is subdivided into multiple turns, with adjacent turn ends connected to separate adjacent commutator segments (three turns → segments 1–3, 2–4, 3–5).
- Rotating-armature three-phase (Figs. X–XI). Twelve rotor poles in groups of three same-sign poles; three secondary windings 120° apart, star-connectable; each phase winding passes twice around a group of three poles.
- Rotating-armature DC → DC (Figs. XII–XIV). Secondary turns encircling three poles (Fig. XII) or four poles (Fig. XIV).
- Stationary two-phase transformer (Fig. XV). Laminated soft-iron sheets with concentric inward poles; primary coils on each pole with one end connected to a coil in the opposite quadrant; two secondary windings each encircling two poles, each seeing "four inductions for each winding in one cycle."
Related claims in the same patent
- Self-induction and sparking. The series interconnection of primary coils and the commutator segment arrangement "avoid a great part of the effects of self-induction" and eliminate sparking "to a remarkable extent."
- Demagnetization avoidance. "At a certain time, the conductors carrying the current of one phase will have no demagnetizing effect on the poles of the armature. This takes place when the induced current flows between adjacent poles having the same polarity."
- Efficiency by armature length. "The efficiency of the motor-generator may be further increased by increasing the length of the armature, since the counter-electromotive force is produced mainly by self-induction, and self-induction is proportional to the square of the number of turns."
Evidence status
The patent asserts these operating principles; it reports no measured efficiency, no test results, and no third-party verification. The Figure Vc area argument is a geometric illustration of the stated principle, not experimental data. The demagnetization and self-induction statements are adjacent in spirit to lenz-law-cancellation claims, but the patent's claim is about commutation and demagnetization, not a Lenzless claim per se.
Related
Source notes & attribution
- https://rexresearch.com/angelo/angelo.htm