Provide PLECS sample files for XML reverse-engineering

[tinix84]

Context

Dependency for #55 (PLECS exporter). We need 4 sample .plecs files to reverse-engineer the XML schema before implementing the exporter.

Place all files in tests/testData/plecs/.

---

File 1: simple_inductor.plecs

Topology: Single-winding gapped inductor

Parameter	Value
Core shape	E32/16/9 (simplified as single magnetic path)
Core material	N87, μᵣ = 2200
Core cross-section	A = 83.2 mm² = 83.2e-6 m²
Core magnetic path length	l_core = 72.7 mm = 72.7e-3 m
Air gap length	l_gap = 1.0 mm = 1.0e-3 m
Air gap cross-section	A_gap = 83.2 mm² (same as core)
Winding	N = 20 turns

Magnetic circuit (series loop):

Winding (N=20)
  │
  ├── Constant Permeance "Core"    P_core = μ₀·μᵣ·A/l = 4π×10⁻⁷ × 2200 × 83.2e-6 / 72.7e-3 ≈ 3.164e-6 Wb/A·t
  │
  ├── Constant Permeance "AirGap"  P_gap  = μ₀·A/l     = 4π×10⁻⁷ × 83.2e-6 / 1.0e-3     ≈ 1.045e-7 Wb/A·t
  │
  └── Magnetic Ground

Electrical side: Leave winding terminals unconnected or connect a voltage source if needed.

---

File 2: transformer.plecs

Topology: Two-winding transformer with core losses, no air gap

Parameter	Value
Core shape	E42/21/15 (simplified as single magnetic path)
Core material	N87, μᵣ = 2200
Core cross-section	A = 178 mm² = 178e-6 m²
Core magnetic path length	l_core = 97.2 mm = 97.2e-3 m
Air gap	None (ungapped)
Primary winding	N₁ = 24 turns
Secondary winding	N₂ = 12 turns
Core loss equivalent	Rm = 5.0e6 A·t·s/Wb

Magnetic circuit:

         ┌── Winding "Primary" (N=24)
         │
Node_A ──┤── Winding "Secondary" (N=12)
         │
         ├── Constant Permeance "Core"          P_core = μ₀·μᵣ·A/l ≈ 5.060e-6 Wb/A·t
         │
         ├── Magnetic Resistance "CoreLoss"     Rm = 5.0e6 A·t·s/Wb  (in series with core permeance)
         │
         └── Magnetic Ground

Both windings connect to the same magnetic node (Node_A). Permeance and Magnetic Resistance in series between Node_A and Ground.

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File 3: saturable_inductor.plecs

Topology: Single-winding gapped inductor with nonlinear core

Parameter	Value
Core shape	E32/16/9
Core material	N87 — use Saturable Core with BH curve
Core cross-section	A = 83.2 mm² = 83.2e-6 m²
Core magnetic path length	l_core = 72.7 mm = 72.7e-3 m
Air gap length	l_gap = 0.5 mm = 0.5e-3 m
Air gap cross-section	A_gap = 83.2e-6 m²
Winding	N = 20 turns

Magnetic circuit:

Winding (N=20)
  │
  ├── Saturable Core "Core"        A = 83.2e-6 m², l = 72.7e-3 m, BH curve = N87
  │
  ├── Constant Permeance "AirGap"  P_gap = μ₀·A/l = 4π×10⁻⁷ × 83.2e-6 / 0.5e-3 ≈ 2.091e-7 Wb/A·t
  │
  └── Magnetic Ground

For the Saturable Core BH curve, use N87 data (at least 5-10 B-H points from 0 to 0.4 T).

---

File 4: ecore_transformer.plecs

Topology: E-core transformer with explicit 3-leg magnetic circuit and center-leg air gap

Parameter	Value
Core shape	E42/21/15
Core material	N87, μᵣ = 2200
Center leg cross-section	A_center = 178 mm² = 178e-6 m²
Center leg length	l_center = 42 mm = 42e-3 m
Outer leg cross-section	A_outer = 89 mm² = 89e-6 m²
Outer leg length	l_outer = 42e-3 m
Top/bottom plate length	l_plate = 27.6 mm = 27.6e-3 m (each side)
Top/bottom plate cross-section	A_plate = 89e-6 m²
Center leg air gap	l_gap = 1.0 mm, A_gap = 178e-6 m²
Primary winding	N₁ = 24 turns (on center leg)
Secondary winding	N₂ = 12 turns (on center leg)

Magnetic circuit (3-branch, simplified):

             Node_Top
            /    |    \
     P_outer_L   |   P_outer_R
           |     |     |
           |   P_gap   |
           |     |     |
           |  Node_W   |
           |     |     |
           |  Winding "Pri" (N=24)
           |  Winding "Sec" (N=12)
           |     |     |
           |  P_center |
            \    |    /
             Node_Bot
                │
          Magnetic Ground

Element	Formula	Value
P_center	μ₀·μᵣ·A_center/l_center	≈ 1.172e-5 Wb/A·t
P_outer_L	μ₀·μᵣ·A_outer/(l_outer + 2·l_plate)	≈ 2.530e-6 Wb/A·t
P_outer_R	same as P_outer_L	≈ 2.530e-6 Wb/A·t
P_gap	μ₀·A_gap/l_gap	≈ 2.237e-7 Wb/A·t

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Acceptance Criteria

• All 4 .plecs files committed to tests/testData/plecs/
• Files open correctly in PLECS
• Parameter values match the specs above