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Regulator for high field current generators

Aviation Mechanic General (AMG) practice question 8 of 41 on Fundamentals of Electricity and Electronics. ACS element AM.I.A.K10 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONVibrating-type voltage regulators cannot be used with generators that require a high field current because the contacts pit or burn. Which type of regulator do heavy-duty generator systems use instead?

  1. AA carbon pile voltage regulator
  2. BA three-unit regulator with a reverse current cut-out
  3. CA vibrating regulator with a larger dashpot
Show the answer and explanation

Correct answer: A. A carbon pile voltage regulator

  • A — correct The handbook states that heavy-duty generator systems require a different type of regulator, such as the carbon pile voltage regulator.
  • B — incorrect The three-unit regulator is used on many light aircraft and its voltage unit works like the vibrating-type regulator; it is not the answer for high field current.
  • C — incorrect The dashpot only damps the vibrating regulator to prevent hunting; it does not solve the contact pitting caused by high field current.

BACKGROUND

Voltage regulation requires a regulating unit to sample the generator output, compare it with a reference, and adjust the field excitation to bring the output back within limits. In a vibrating-type regulator a solenoid opens and closes a contact that inserts or shorts a field rheostat, holding the terminal voltage to an average value; a dashpot damps the action to prevent hunting. Because the contacts pit or burn when they must handle high field current, vibrating-type regulators cannot be used with generators that require high field current. Heavy-duty generator systems therefore use a different regulator, such as the carbon pile voltage regulator. Many light aircraft use a three-unit regulator that combines a voltage regulator, a current limiter, and a reverse current cut-out.

STUDY TIP

Link regulator type to generator size: vibrating contacts for light loads, carbon pile for heavy-duty systems.

KEY POINTS

  • A regulator samples output, compares it with a reference, and adjusts field excitation.
  • Vibrating-type regulators are unsuitable for high field current because the contacts pit or burn.
  • Heavy-duty systems use a carbon pile voltage regulator.

SOURCES

  • FAA-H-8083-30B ch12 "Voltage Regulation of Generators" (vibrating-type regulator and carbon pile paragraph preceding "Three Unit Regulators")
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-30B Aviation Maintenance Technician Handbook – General, 14 CFR part 43 and part 65. Regulations and handbooks are revised; confirm details against the current edition.