In using a portable growler for the purpose of locating a shorted stator coil in an AC motor as shown in the illustration, what statement is true as the feeler is moved from slot to slot around the stator? Illustration EL-0200

Correct Answer: Option D — The feeler will vibrate in synchronism with the 60 Hz AC power source and produce a growling noise when the feeler is moved over a slot containing a shorted coil.

A portable growler induces a magnetic field in the stator core; a shorted coil acts as a closed secondary transformer winding, producing high circulating current that vibrates a steel feeler blade loudly. This IEEE 45 and 46 CFR Subchapter J testing method isolates turn-to-turn shorts.