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Designs electromagnets, motors, generators, and transformers from first principles: sizing, topology selection, loss analysis, and thermal validation.
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/agent-almanac:design-electromagnetic-deviceThis skill is limited to the following tools:
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Design a practical electromagnetic device by specifying performance requirements, selecting an appropriate topology, calculating design parameters from electromagnetic first principles, analyzing losses and efficiency, and validating the design against physical constraints including thermal limits and material saturation.
Design a practical electromagnetic device by specifying performance requirements, selecting an appropriate topology, calculating design parameters from electromagnetic first principles, analyzing losses and efficiency, and validating the design against physical constraints including thermal limits and material saturation.
Define the complete set of design targets before selecting a topology:
Primary performance metric: The single most important specification:
Secondary specifications: Efficiency target (%), maximum temperature rise above ambient (K), duty cycle (continuous, intermittent, or pulsed), physical envelope (maximum diameter, length, weight).
Supply constraints: Available voltage and current, frequency (DC or AC with specified Hz), waveform (sinusoidal, PWM, trapezoidal).
Environmental conditions: Ambient temperature range, cooling method (natural convection, forced air, liquid), altitude (affects air cooling), and vibration/shock requirements.
## Design Requirements
- **Device type**: [electromagnet / motor / generator / transformer]
- **Primary specification**: [value with units]
- **Efficiency target**: [%]
- **Supply**: [voltage, current, frequency]
- **Thermal limit**: [max temperature rise in K]
- **Size constraint**: [dimensions or weight]
- **Duty cycle**: [continuous / intermittent (on-time/off-time) / pulsed]
Expected: A complete, quantified set of requirements with no ambiguous specifications. Every requirement has a numerical value and units.
On failure: If requirements conflict (e.g., high torque in a very small volume with high efficiency), identify the tradeoff explicitly and ask the designer to prioritize. Electromagnetic devices obey fundamental scaling laws: force scales with volume, losses scale with surface area, and thermal limits constrain the power density.
Choose the device configuration that best matches the requirements:
Electromagnet topologies:
Motor topologies:
Generator topologies: Motors operated in reverse. A BLDC motor becomes a BLDC generator (back-EMF becomes output). An induction motor becomes an induction generator when driven above synchronous speed. Permanent magnet generators are preferred for small-scale (wind, hydro).
Transformer topologies:
## Topology Selection
- **Topology chosen**: [specific configuration]
- **Justification**: [why it matches the requirements]
- **Key advantages**: [for this application]
- **Key limitations**: [and mitigation strategy]
- **Alternatives considered**: [and why rejected]
Expected: A justified topology selection with clear reasoning tied to the requirements from Step 1, including acknowledged limitations.
On failure: If no standard topology meets all requirements, consider a hybrid design (e.g., Halbach array for higher field with less material) or relax a secondary constraint. Document the tradeoff.
Compute the physical dimensions and electrical parameters from electromagnetic principles:
Electromagnet design parameters:
Motor design parameters:
Transformer design parameters:
Magnetic circuit analysis: For devices with cores and air gaps:
## Design Parameters
- **Turns**: N = [value] (primary), N_2 = [value] (if applicable)
- **Wire gauge**: AWG [number] (diameter [mm], area [mm^2])
- **Core dimensions**: A_core = [mm^2], l_core = [mm], l_gap = [mm]
- **Core material**: [type], B_max = [T], mu_r = [value]
- **Winding resistance**: R = [Ohms]
- **Operating current**: I = [A], current density J = [A/mm^2]
- **Key performance**: [B-field / torque / voltage ratio = calculated value]
Expected: Numerical values for all physical dimensions and electrical parameters, derived from electromagnetic equations with units checked at each step.
On failure: If the required turns do not fit in the available winding space, either increase the core size (larger window area), use finer wire (higher current density, but more heating), or reduce the performance target. If the core operates above B_max, increase the core cross-section or add turns (to reduce the flux for the same performance via a larger NI product with a larger gap).
Quantify every loss mechanism and compute overall efficiency:
Copper losses (I^2 R):
Core losses (hysteresis + eddy current):
Eddy current losses in conductors and structure:
Mechanical losses (motors and generators):
Efficiency calculation:
## Loss Analysis
| Loss Mechanism | Formula | Value (W) | Fraction of Total |
|---------------|---------|-----------|-------------------|
| Copper (I^2R) | [expression] | [W] | [%] |
| Core hysteresis | [expression] | [W] | [%] |
| Core eddy current | [expression] | [W] | [%] |
| Mechanical (if applicable) | [expression] | [W] | [%] |
| **Total losses** | | [W] | 100% |
- **Efficiency**: eta = [%]
- **Temperature rise estimate**: Delta_T = P_total / (h * A_surface) = [K]
Expected: A complete loss breakdown with each mechanism quantified, total efficiency computed, and temperature rise estimated to verify thermal feasibility.
On failure: If efficiency is below the target, identify the dominant loss mechanism and address it: copper losses dominate in small devices (increase wire size or reduce turns), core losses dominate at high frequency (switch to lower-loss core material or reduce B_max), mechanical losses dominate at high speed (improve bearings). If the temperature rise exceeds the thermal limit, increase the cooling (forced air, heat sinks) or reduce the power density.
Verify that the design meets all specifications and is physically realizable:
Performance verification:
Saturation check:
Thermal check:
Dimensional check:
Design margin and sensitivity:
## Design Validation
| Requirement | Target | Achieved | Margin |
|------------|--------|----------|--------|
| [Primary metric] | [value] | [value] | [%] |
| Efficiency | [%] | [%] | [%] |
| Temperature rise | < [K] | [K] | [K margin] |
| Envelope | [dimensions] | [dimensions] | [fits / exceeds] |
## Sensitivity Analysis
| Parameter | Nominal | +10% Effect on Primary Metric | Most Sensitive? |
|-----------|---------|-------------------------------|----------------|
| Current | [A] | [+/- %] | [Yes/No] |
| Turns | [N] | [+/- %] | [Yes/No] |
| Air gap | [mm] | [+/- %] | [Yes/No] |
| mu_r | [value] | [+/- %] | [Yes/No] |
Expected: All requirements met with documented margins, thermal feasibility confirmed, and the most sensitive design parameter identified.
On failure: If a requirement is not met, iterate by adjusting the topology (Step 2), design parameters (Step 3), or loss mitigation strategy (Step 4). If the design is thermally infeasible, consider: reducing the duty cycle, increasing the size (more surface area for cooling), switching to a higher temperature insulation class, or adding active cooling. Document each iteration.
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