Excessive buzzing of AC contactors may be...

🔍 Key Concepts

• AC contactor construction – especially the armature, core, and shading (shading rings) parts • Purpose of shading coils in AC magnetic devices (reducing chatter/buzz due to alternating current going through zero 60 times per second) • Difference between problems caused by coil faults vs. mechanical/flux-smoothing parts like shading coils or arc shields

💭 Think About

• Think about what happens to an AC magnetic field 60 times per second and why a contactor might try to pull in and drop out repeatedly, creating a buzz. • Which part in an AC contactor is specifically added to smooth out or delay part of the magnetic flux so the armature doesn’t chatter when the current crosses zero? • Of the faults listed, which one would directly affect that special part whose job is to prevent buzzing, rather than just causing overheating or failure to pick up at all?

✅ Before You Answer

• Identify which option refers to a part whose primary function is to reduce chatter/buzz in AC magnetic devices. • Check which fault would cause loss of the ‘holding’ effect of the magnetic field at the moment when the AC current passes through zero. • Verify that your choice is related to magnetic flux timing/smoothing, not just general damage or high voltage.

Excessive buzzing of AC contactors may be caused by what condition?

burnt arc shields

shorted armature coils

a broken shading coil

high voltage

🔍 Key Concepts

💭 Think About

✅ Before You Answer