Question
What is used to suppress radio frequency interference from a line-driven AC motor?
Answer Options
- A) A high-pass filter in series with the motor’s power leads
- B) A brute-force AC-line filter in series with the motor’s power leads
- C) A bypass capacitor in series with the motor’s field winding
- D) A bypass choke in parallel with the motor’s field winding
Correct Answer: B
Explanation
Line-driven AC motors (used in appliances, power tools, etc.) can generate significant broadband noise due to arcing at the brushes or commutation. This noise can enter the electrical system and be radiated or conducted throughout the house and neighborhood, causing wide-ranging radio frequency interference (RFI).
The best way to suppress this noise at its source is to use a brute-force AC-line filter in series with the motor’s power leads. This filter is essentially a combination of large capacitors and chokes designed to suppress the high-frequency RF noise generated by the motor, ensuring that only the desired low-frequency AC power passes through to the motor itself.
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