Design the power system for a classified prototype aerial platform, then switch sides of the table and evaluate the competing proposals as a government customer.
:::{admonition} At a glance :class: key-concept **Groups of 2–4.** Three Gradescope submissions, **1 point each**. Kicked off at **Lesson 12**; work days are **Lessons 13 and 14**. Submission 1 is due **Monday 14 September at 2359**; Submissions 2–3 are due **Wednesday 16 September at 2359**. Gradescope is authoritative for all deadlines. ::: ## The Problem Your team works both sides of the contracting process. - **Part 1 — you are the contractor.** Design a power system that energizes eight electrical loads to specification. You want a better design than the other teams. - **Part 2 — you are the government evaluator.** You receive the other teams' proposals and rate them objectively with a decision matrix. You do not see anyone else's design until your Part 1 is submitted. ## System Requirements The system must properly energize the following eight loads. All AC voltages are RMS and apply to a 60 Hz system. Label the loads A–H in your design, matching the proposal diagrams. | Load | Description | Voltage | Specification | | --- | --- | --- | --- | | A | Recirculation fans | 240 Vrms | 8 kW, pf = 0.8 lagging | | B | Fuel pumps | 240 Vrms | 12 kVA, pf = 0.6 lagging | | C | Cabin lighting | 120 Vrms | 6 kW, pf = 0.8 lagging | | D | Cabin fans | 120 Vrms | 5 hp, $\eta = 88.89\%$, pf = 0.8 lagging | | E | Auto-pilot & controls | 48 V DC | $R = 2\ \Omega$ | | F | Brake power | 48 V DC | 0.75 hp, $\eta = 85\%$ | | G | Communications | 24 V DC | 500 W | | H | Flight displays | 24 V DC | 25 A | Every load type here is one you learned to handle in Lessons 6–10. Nothing in this table is new. ## Constraints A proposed system must comply with **all** of the following: - All loads connected to a bus and powered to the Table 1 specifications. - Powered by a generator **not exceeding 30 kW of real power** during normal operation, attached to either a 240 Vrms or 120 Vrms bus. - A resistor of **0.016 Ω – 0.022 Ω** between the generator and the first bus, to capture wiring losses. No cost is associated with this resistor. - Only the **COTS converters** listed in Table 2 of the handout may be used — in any quantity; the same catalog item may be used more than once, and each instance is priced and counted separately. - Every load, bus, and piece of conversion equipment gets **its own circuit breaker**. - Cost of conversion and protection must not exceed **\$500,000**. - Volume of conversion equipment must not exceed **25 m³**. :::{admonition} Compliance is not a score :class: key-concept A design that violates any constraint is not a *worse* design — it is a **non-compliant** one. Check compliance before you spend any time optimizing. ::: ## Evaluation Criteria The solicitation states the priority directly: **cost is weighted 2× efficiency, and efficiency is weighted 2× volume.** That is a ratio of 4 : 2 : 1, so: | Measure | Ratio | Weight | Direction | Normalize with | | --- | --- | --- | --- | --- | | Cost | 4 | 0.571 | smaller is better | $x_{\min}/x$ | | Efficiency | 2 | 0.286 | bigger is better | $x/x_{\max}$ | | Volume | 1 | 0.143 | smaller is better | $x_{\min}/x$ | Two of the three are smaller-is-better. Getting a direction backward is the fastest way to lose the Submission 2 point — see [Objective 1.8](../Block1Reading/Obj08/ECE215_Obj08_Reading). ## Method Work **backward from the loads**, exactly as in Lessons 8–10: 1. Find the real power and current each load demands. 2. Group loads onto buses by voltage. 3. Work back through each converter: $P_{in} = P_{out}/\eta$. 4. Sum at each bus, then step back to the generator. 5. Add the wiring-resistor loss **last**, using the *generator* current: $P = I^2R$. 6. Verify the generator total is under 30 kW. :::{admonition} The two mistakes teams make every semester :class: key-concept **Summing apparent power against the generator limit.** The 30 kW cap is on **real power**. Load B is given as 12 kVA at pf = 0.6 — that is 7.2 kW real, not 12. Sum $P$ against the limit, but size the *wiring* from the actual current, which follows $S$. **Using load current in the wiring-resistor loss.** That resistor sits between the generator and the first bus, so it carries the **total generator current** — not any individual load's. ::: ## Deliverables Three Gradescope submissions, **1 point each**, graded on specifications. ### Submission 1 — system design *(group)* Due **Monday 14 September at 2359** (before Lesson 14). Upload **two files**: your design and analysis as a **PDF**, and the completed **Design Summary workbook** built from the template below. - [ ] System design is easy to read, clearly labeled, and meets every design requirement. See the example bus diagram (Figure 1) in the handout below for the drawing conventions. - [ ] Mathematical analysis provided, legible, and clearly labeled. Gradescope returns an automatic **consistency report** on your workbook — whether your own numbers agree with each other and with the handout's catalogs. It is **advisory feedback only**; your instructors grade the two specifications above. ### Submission 2 — decision matrix *(group)* - [ ] Decision matrix filled out correctly. **Auto-graded — trivial math errors will not earn credit.** Rounding errors are fine. - [ ] Supporting analysis provided, as clearly labeled handwriting or an organized spreadsheet. ### Submission 3 — engineering analysis *(individual)* - [ ] Questions answered correctly with **concise** technical writing. Lengthy responses will not earn credit. ## Authorized Resources - Calculator and computational tools — Excel, MATLAB, Google Sheets, Python - The ECE 215 equation sheet - Slides, class notes, and the readings on this site - Practice problems - **GenAI: Level 2 only** (see the AW GenAI policy) - Collaboration with cadets **in your project group**, and EI from ECE instructors :::{admonition} Note on seeking EI from ECE 315 instructors :class: warning This project has differences in power computations from the ECE 315 Project 1. Mention that you are in ECE 215 when you ask. ::: ## Files