When testing for blown fuses in a...

🔍 Key Concepts

• Three-phase circuits and how fuses are arranged in each phase leg feeding a motor • Difference between using a continuity/ohmmeter (for de-energized circuits) and a voltage tester (for energized circuits) • What it means, in practice, to "test across the tops" or "across the bottoms" of fuses in a three-phase fuse block

💭 Think About

• Ask yourself: if all three fuses are good and the circuit is energized, what voltage would you expect between phases at the fuse terminals? What changes when one fuse is blown? • Think about safety: which methods require the circuit to be de-energized, and which methods require it to be energized? How does that affect what you can actually detect? • Visualize a three-pole fuse holder: where is the line side and where is the load side of each fuse? How would a blown fuse affect continuity and voltage readings at each side?

✅ Before You Answer

• Confirm whether the described method can actually distinguish between a blown fuse and a good fuse in a three‑phase system, not just show a path exists somewhere. • Check if the method depends on the circuit being energized or de-energized, and whether that matches how the instrument (ohmmeter vs. voltage tester) is properly used. • Verify whether measuring only at the tops or only at the bottoms of the fuses would show a difference between phases if one fuse is open.

When testing for blown fuses in a three-phase supply circuit to a motor, what would be an acceptable method?

ensure the circuit is de-energized, and then use an ohmmeter or continuity tester connected across the bottoms of the fuses

ensure the circuit is de-energized, and then use an ohmmeter or continuity tester connected across the tops of the fuses

apply a voltage tester diagonally across the tops of the fuses and the bottoms of the other fuses

apply a voltage tester across the tops of the fuses

🔍 Key Concepts

💭 Think About

✅ Before You Answer