Every operating point the drive can reach: speed along one axis, load current along the other, efficiency as height and colour. The clipped far edge of the surface is the voltage-circle limit iq_max(rpm) — the same curve as the Curves tab. The current cap and no-load drag are applied when set. The load axis tops out just above the peak-power current (or at the cap) — higher currents are reachable only near stall and would crush the useful region.

Steady-state only, with id = 0 — no field weakening, so a drive with FW can exceed base speed and these curves. L and R_s are taken constant: no magnetic saturation (saturating L shifts high-current numbers) and no temperature rise (hot R_s shifts low-speed numbers). No switching losses; iron, windage and friction are modelled only if a no-load measurement is entered — drag torque is then taken proportional to speed through that point, which is a one-point fit: it understates constant friction at low speed and any ω² windage growth at high speed. Without it, copper is the only loss modelled. The bus is assumed stiff; sag under load lowers v_lim and every curve with it. The margin input exists because real current controllers need voltage headroom to regulate — running at 100 % utilisation is exactly how drives lose regulation and desync. Trapezoidal mode is a fundamental-equivalent model of 120° six-step (±5 % versus exact waveform simulation); timing advance is modelled as the current fundamental leading the back-EMF by the advance angle, and all displayed currents remain fundamental amplitudes (block flat-top ≈ iq/1.103, RMS shown includes the block harmonics). The stall figure is the resistance-limited current v_lim/R_s — the point where the entire inverter voltage ceiling is dropped across the winding resistance (line-to-line: √3·R_phn·iq = V_bus) — and real motors reach thermal limits far below it.