Practice question · NEC Table 430.7(B)

What Is the Locked-Rotor kVA of a 10 HP Motor?

By Mason Garry, Master Electrician · October 8, 2026 · 2 min read

Locked-rotor kVA comes from a simple formula — code letter × HP — but the table gives you a range, and the exam tests whether you pick the right end of it. Read the adjective in the stem.

Answer: A) 62.9 kVA. Code letter G tops out at 6.29 kVA per HP — 10 × 6.29 = 62.9 kVA maximum.

Where to Find It

Open your Code book to Table 430.7(B). Find code letter G down the left column: the range is 5.6–6.29 kVA per HP. Multiply the per-HP value by the motor's horsepower: 10 × 6.29 = 62.9 kVA. Tab it with the formula: code letter × HP = locked-rotor kVA.

Why This Works

The locked-rotor code letter on a motor nameplate tells you how many kVA per horsepower the motor draws at startup, with the rotor held still. Table 430.7(B) lists a range for each letter — G spans 5.6 to 6.29 kVA per HP. The question asks for the maximum, so you take the top of the range: 10 × 6.29 = 62.9 kVA.

This is one of the cleanest lookups on the exam: find the letter, multiply by the HP, done. The numbers look big next to the 10 HP rating — that's normal. Locked-rotor current is several times running current, which is exactly why the branch-circuit protection math in Article 430 gets its own article instead of living in the general overcurrent rules.

More motor table reps: our study guides cover the Article 430 lookups the exam hits hardest.

The Trap

Option B (56 kVA) is the trap — it's 10 × 5.6, the bottom of the range. If the stem said "minimum," 56 would be right. It says "maximum," so you take the top. The exam loves testing whether you read the adjective instead of grabbing whichever number you multiplied first. Option C (10 kVA) catches anyone who confuses HP with kVA — different units, different thing.

Exam Tip

Whenever a code-letter question says "maximum," use the high end of the range. Whenever it says "minimum," use the low end. Write "code letter × HP = locked-rotor kVA" on your tab for Table 430.7(B) — the formula tells you the two things to find, and the adjective tells you which end of the range to use.

Keep Drilling

This is one of 33 NEC topics. Sparky's 1,087 codebook-first questions drill all of them — every question a lookup rep with your book open, 15 minutes a day.