A maintenance electrician scans a 3-phase motor starter with an infrared camera. Phase A is 45°C, Phase B is 46°C, and Phase C is 95°C. What is the most likely cause of this discrepancy?
Answers
AThe infrared camera needs to be recalibrated
BPhase C is carrying normal load current
CA loose connection on Phase C causing high resistance heating
DThe motor has a blown Phase A fuse
Correct answer: C — A loose connection on Phase C causing high resistance heating
A single hot phase in a 3-phase connection is almost always caused by high resistance at a loose, corroded, or failing termination.
MIFOTRA exam practicealigned to CompTIA (General IT) / BICSI·1 mark·Easy