Does the prototype pass the engineering requirement?
Compare measured efficiency and current with the deployment gates.
The question
You are in a fictional campus interview for a Graduate Engineer Trainee role. Your team built a small motor prototype. You recorded terminal measurements, shaft torque and speed. The intended deployment requires at least 60% terminal-to-shaft efficiency and at most 22 A. The lab supply used for measurements is rated above the measured currents.
| Value | |
|---|---|
| Terminal voltage (V) | 24 |
| Terminal current (A) | 18 |
| Shaft torque (N·m) | 6 |
| Angular speed (rad/s) | 50 |
| Minimum measured efficiency (%) | 60 |
| Maximum deployment current (A) | 22 |
Use terminal voltage times current for electrical input and shaft torque times angular speed for mechanical output.
“Explain what your test supports and whether the prototype meets both deployment gates.”
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A strong answer, step by step
Open each step in turn. This is one strong answer, not the only one.
Step 1: Identify the inputs
What would you do here? Open the move you’d make.
Compute 300 W shaft output and 432 W input.
The strong move. Use a single measurement boundary and the units in the packet.
Divide input power by output power.
Tempting, but it misses something. The efficiency measures delivered shaft power as a share of terminal power.
See how a strong candidate says it
“The terminal electrical input is 24 V times 18 A, or 432 W. The mechanical shaft output is 6 N·m times 50 rad/s, or 300 W. Efficiency compares the shaft output with the terminal input.”
Why it works: Use a single measurement boundary and the units in the packet.
Step 2: Explain what passed
What would you do here? Open the move you’d make.
Report both gates at the measured duty point.
The strong move. The result supports the measured duty point.
Say the prototype is ready for every load.
Tempting, but it misses something. The opening packet gives one measured speed and torque condition.
See how a strong candidate says it
“The measured efficiency is about 69.4%, and current is 18 A. Both gates pass for this baseline run. I took the measurements, and I would describe this speed and torque when reporting the result.”
Why it works: The result supports the measured duty point.
Step 3: Answer the new duty point
The panel supplies a second measured run at 60 rad/s and 24 A. Terminal voltage stays at 24 V, torque stays at 6 N·m and the two deployment gates still apply.
What would you do here? Open the move you’d make.
Report that the new duty point fails the current limit.
The strong move. Both efficiency and current must pass.
Approve because efficiency still exceeds 60%.
Tempting, but it misses something. The current is 24 A, above the separate 22 A maximum.
See how a strong candidate says it
“The new shaft output is 360 W and terminal input is 576 W. Efficiency is 62.5%, above the 60% minimum. Current is 24 A, which exceeds the deployment limit by 2 A. I would report a failed deployment gate.”
Why it works: Both efficiency and current must pass.
Step 4: Revise the recommendation
What would you do here? Open the move you’d make.
Ask for a review and a repeat check before recommending deployment.
The strong move. The lab result and deployment decision use the specified gates.
Use the lab supply’s higher rating as the new limit.
Tempting, but it misses something. The bench supply can measure the run. The intended deployment still has a 22 A limit.
See how a strong candidate says it
“I would tell the supervisor the prototype fails the second duty point. I would ask for a design or requirement review and repeat the measurement against both gates before recommending deployment.”
Why it works: The lab result and deployment decision use the specified gates.
The answer, in short
- Decision
- Withhold the deployment recommendation for the second duty point.
- Because
- Efficiency passes, and current exceeds the deployment limit.
- What would change it
- A tested design that meets both gates would change the recommendation.
Common traps
- Dividing power in the wrong direction.
- Using one passing measurement to cover every duty point.
Check your answer
- I used the correct power units.
- I stated what I measured.
- I compared both deployment gates.
- I updated the recommendation under the new run.
Last reviewed Nov 10, 2026