Stephen-style 3-phase alternator VIC drive: no SCR; rpm sets frequency, rotor field current sets amplitude

From Scotchn's LTspice package (Kevin_StephenMeyers_3Phase, 3PH_WYE.sub + WFC_Behave.sub, reviewed 2026-09-14). Scotchn states the 3PH_WYE block is an ALTERNATOR and that Stephen's circuit contains NO SCR.

TOPOLOGY: 3-phase wye alternator -> three transformers (K=0.995, Lpri/Lsec, ratio sqrt(Lsec/Lpri)) -> blocking diode -> resonant charging chokes (with series DCR) -> water capacitor cell. No active switch anywhere. Rectification is the automotive 6-diode arrangement implied by three branches.

• CONSEQUENCES DERIVED:
• 1. Drive frequency is mechanical — f = (poles x rpm)/120. The file's Fgen=620 Hz corresponds to ~6200 rpm on a 12-pole machine, i.e. roughly 2500 engine rpm at 2.5:1 pulley. Ripple/pulse rate = 6 x f_alt = 3720 Hz at that point and it TRACKS CRANK SPEED with no electronics. This matches the 423 DA finding that gate rate is crank speed (notebook #3368).
• 2. With no SCR there is no latch/commutation problem at all. Scotchn's standing "SCR latching/unlatching" open issue does not exist in this architecture.
• 3. The two remaining control knobs are both native to an alternator: ROTOR FIELD CURRENT sets output amplitude (the voltage-ladder / amplitude-attenuation lever), and RPM sets frequency. Closed-loop control reduces to field-current regulation plus pulley ratio.
• 4. Cost of removing the SCR — no independent gate/duty control. Gating in Stan's sense (pulse train on/off) is unavailable unless reintroduced downstream.
• 5. Resonance is only met in one rev band — for a 5 kHz tank, 6 x f_alt = 5000 -> f_alt ~ 833 Hz -> ~3300 engine rpm. Either a defect or a deliberate powerband, depending on tank design.
• 6. Model caveat found — 3PH_WYE defaults Rph=1u, Lph=1p are ideal and impose no synchronous reactance, which is why the first run drew +/-16 A. Realistic starting values Rph=0.1, Lph=200u give Xs = 0.78 ohm per phase at 620 Hz.

STATUS: unverified by simulation or bench. Derived from file inspection plus Scotchn's statement of intent. Contrast with Stan's own SCR/variac practice, which Scotchn runs on his bench.