What is used to suppress radio frequency interference from a line-driven AC motor?
A high-pass filter in series with the motor’s power leads
A brute-force AC-line filter in series with the motor’s power leads✓Correct answer
A bypass capacitor in series with the motor’s field winding
A bypass choke in parallel with the motor’s field winding
Explanation
Brush and commutator noise leaves a line-driven motor by conduction along its power leads, so the cure is a mains-rated interference filter inserted in those leads. A capacitor or choke placed in series or parallel with the field winding does not interrupt that conducted path.